Patent Publication Number: US-11388541-B2

Title: Audio communication system and method

Description:
TECHNOLOGICAL FIELD 
     The present invention is in the field of Human-Machine Interface, utilizing audio communication and is relevant to systems and method for providing hands-free audio communication and generation of 3D auditory space. 
     BACKGROUND 
     Audio communication takes a large portion of human interaction. We conduct telephone conversations, listen to music or sound associated with TV shows and receive alert such as alarm clock or finish of a microwave oven or dishwasher cycle. 
     The natural wave behavior of acoustic signals and the relatively long wavelength results with large spreading of the sound waves and allows people located in a common region to hear the sound and perceive the data carried thereon. 
     Various techniques are known for allowing a user to communication via sound while maintaining privacy of the communication. Between such techniques, best known examples include the telephone receiver and headphones or earphones, all providing relatively low amplitude acoustic signals directed at one or both of the user&#39;s ears. 
     Binaural hearing ability of humans and animals enables them to locate sounds in three dimensions within an auditory space (i.e. to resolve direction and possibly also distance and distinguish between sounds arriving from different locations in the auditory space). 
     This is possible because the brain infers the direction and possibly also the distance/location of the sound source by comparing the binaural sounds sensed by the left and right ears to identify sound modifications/differences (sound cues) between the two ears that are indicative of the direction/location of the sound source. Among the sound cues included are time difference of arrival, and intensity difference due to a difference in the acoustical paths of propagation of the sound from the source to the two ears respectively, as well as spectral (frequency spectrum) modifications caused by interaction of the sounds arriving from the sound source with the head/ears anatomy, in which the original source sound is modified before it enters the ear canal for processing by the auditory system. The brain processes these modifications of the sounds captured by the two different ears to infer the direction and possibly distance of the sound source(s). 
     An illusion of three dimensional (3D) auditory space, a so-called virtual auditory space (VAS), can be generated by headphones by utilizing appropriate filtering of sounds presented over the headphones. When utilizing headphones, a head-related transfer function (HRTF) is typically used for carrying out appropriate filtering of the sounds presented over each individual one of the headphones for creating the VAS. 
     Generally, the head-related transfer function (HRTF) is a response function characterizing how an ear of a user receives sound from a point in space. As indicated above, properties of the user&#39;s head and ears (e.g. size and shape and/or mechanical properties thereof), transform the sound sensed by the eardrum and thereby affect how sounds from different points in space are perceived, and particularly introduce different spectral modifications to sounds arriving to the user from different directions relative to the user. Typically, some sound frequencies (e.g. from 2-5 kHz) are amplified, while others are attenuated, while the parameters of the of the amplification/attenuation generally depend on the direction and possibly also distance of the sound source. Also as indicated above, time delay and intensity difference are introduced to sounds arriving from the same source to the left and right ears of the user, due to a difference in the acoustical path from the source to the two ears respectively. 
     A virtual auditory space (VAS) sensation can be created, for example by headphones by utilizing a couple of HRTFs for two ears of the user respectively, to synthesize binaural sound that is perceived by the user as coming from a particular direction/location in space. The HRTFs introduce spectral modifications to the sounds depending on the relative directions from which they arrive to the respective ears. The HRTF presents the spectral modifications applied by the head to sound propagating from a certain direction in free air until the sound arrives and is sensed by the eardrum of a particular ear. Moreover, typically proper relative time delays and intensity differences are also respectively introduced to the sounds transmitted to the two ears whereby the magnitude of the time delay and intensity difference depends on the different trajectories/paths (direct or indirect) of sounds from the particular direction/location of a sound source towards the respective ears. 
     Techniques developed by the inventors of the present application provide private sound transmitted to a selected user from a remote location. The details of this technique are described in WO 2014/076707 and in WO 2014/147625 both assigned to the assignee of the present application. 
     More specifically, WO 2014/076707 discloses a system and method for generating a localized audible sound field at a designated spatial location. According to this technique, spatially confined audible sound carrying predetermined sound-data is produced locally at a designated spatial location at which it should be heard. Even more specifically, according to the disclosed technique in order to generate the locally confined audible sound carrying the desired sound-data, frequency content of at least two ultrasound beams are determined based on the sound data and the of at least two ultrasound beams are transmitted by an acoustic transducer system (e.g. transducer system including an arrangement of a plurality of ultrasound transducer elements) Then, the spatially confined audible sound is produced at the designated location by the at least two ultrasound beams. For example, the at least two ultrasound beams include at least one primary audio modulated ultrasound beam, whose frequency contents includes at least two ultrasonic frequency components selected to produce the audible sound after undergoing non-linear interaction in a non linear medium, and one or more additional ultrasound beams each including one or more ultrasonic frequency components. Location-data indicative of the designated location is utilized for determining at least two focal points for the at least two ultrasound beams respectively such that focusing the at least two ultrasound beams on the at least two focal points enables generation of a localized sound field with the audible sound in the vicinity of the designated spatial location. 
     WO 2014/147625, which is also assigned to the assignee of the present application, describes a transducer system including a panel having one or more piezo-electric enabled foils/sheets/layers and an arrangement of electric contacts coupled to the panel. The electric contacts are configured to define a plurality of transducers in the panel. Each transducer is associated with a respective region of the panel and with at least two electric contacts that are coupled to at least two zones at that respective region of the panel. The electric contacts are adapted to provide electric field in these at least two zones to cause different degrees of piezo-electric material deformation in these at least two zones and to thereby deform the respective region of the panel in a direction substantially perpendicular to a surface of the panel, and to thereby enable efficient conversion of electrical signals to mechanical vibrations (acoustic waves) and/or vice versa. The transducer of this invention may be configured and operable for producing at least two ultrasound beams usable for generating the spatially confined audible sound disclosed in WO 2014/076707 discussed above. 
     GENERAL DESCRIPTION 
     There is a need in the art for a novel system and method capable of managing private sound (i.e. providing sound to a selected user to be privately consumed/heard by the user) directed to selected one or more users located within certain space. The technique of the present invention utilizes one or more Three Dimensional Sensor Modules (TDSM) associated with one or more transducer units for determining location of a user and determining an appropriate sound trajectory for transmission private sound signals to the selected user, while eliminating, or at least significantly reducing interference of the sound signal with other users, which may be located in the same space. 
     In this connection it should be noted that the Three Dimensional Sensor Modules may or may not be configured for providing three dimensional sensing data when operating as a single module. More specifically, the technique of the present invention utilizes one or more sensor modules arranged in a region of interest and analyzes and processes sensing data received therefore to determine three dimensional data. To this end the TDSM units may include camera units (e.g. array/arrangement of several camera units) optionally associated/including diffused IR emitter, and additionally or alternatively may include other type(s) of sensing module(s) operable sensing three dimensional data indicative of a three dimensional arrangement/content of a sensing volume. 
     The technique of the present invention utilizes one or more transducer units (transducer arrays) suitable to be arranged in a space (e.g. apartment, house, office building, public spaces, vehicles interior, etc. and mounted on walls, ceilings or standing on shelves or other surfaces) and configured and operable for providing private (e.g. locally confined) audible sound (e.g. vocal communication) to one or more selected users. 
     For example, in some implementations of the present invention, one or more transducer units such as the transducer unit disclosed in WO 2014/147625, which is assigned to the assignee of the present application, are included/associated with the system of the present invention and are configured to generate directed, and generally focused, acoustic signals to thereby create audible sound at a selected point (confined region) in space within a selected distance from the transducer unit. 
     To this end, in some embodiments of the present invention the one or more transducer units are configured to selectively transmit acoustic signals at two or more ultra-sonic frequency ranges such that the ultra-sonic signals demodulate to form audible signal frequencies at a selected location. The emitted ultra-sonic signals are focused to the desired location where the interaction between the acoustic waves causes self-demodulation generating acoustic waves at audible frequencies. The recipient/target location and generated audible signal are determined in accordance with selected amplitudes, beam shape and frequencies of the output ultra-sonic signals as described in patent publication WO 2014/076707 assigned to the assigned of the present application and incorporated herein by reference in connection to the technique for generating private sound region. 
     The present technique utilizes such one or more transducer units in combination with one or more Three Dimensional Sensor Modules (TDSMs) and one or more microphones units, all connectable to one or more processing unit to provide additional management functionalities forming a hand-free audio communication system. More specifically, the technique of the invention is based on generating a three dimensional model of a selected space, and enable one or more users located in said space to initiate and respond to audio communication sessions privately and without the need to actively be in touch with a control panel or hand held device. 
     In this connection the present invention may provide various types of communication sessions including, but not limited to: local and/or remote communication with one or more other users, receiving notification from external systems/devices, providing vocal instructions/commands to one or more external devices, providing internal operational command to the system (e.g. privilege management, volume changes, adding user identity etc.), providing information and advertising from local or remote system (e.g. public space information directed to specific users for advertising, information about museum pieces, in ear translation etc.). The technique of the invention may also provide indication about user&#39;s reception of the transmitted data as described herein below. Such data may be further process to determine effectiveness of advertising, parental control etc. 
     To this end the present technique may be realized using centralized or decentralized (e.g. distributed) processing unit(s) (also referred herein as control unit or audio server system) connectable to one or more transducer units and one or more TDSMs and one or more microphone units or in the form of distributed management providing one or more audio communication system, each comprising a transducer unit, a TDSM unit, a microphone unit and certain processing capabilities, where different audio communication systems are configured to communicate between them to thereby provide audio communication to region greater than coverage area of a single transducer unit, or in disconnected regions (e.g. different rooms separated by walls). 
     The processor, being configured for centralized or distributed management, is configured to receive data (e.g. sensing data) about three dimensional configuration of the space in which the one or more TDSM are located. Based on at least initial received sensing data, the processor may be configured and operable to generate a three dimensional (3D) model of the space. The 3D model generally includes data about arrangement of stationary objects within the space to thereby determine one or more coverage zones associates with the one or more transducer units. Thus, when one or more of the TDSMs provides data indicative of user being located in certain location in the space, a communication session (remotely initiated or by the user) is conducted privately using a transducer unit selected to provide optimal coverage to the user&#39;s location. 
     Alternatively or additionally, the technique may utilize image processing techniques for locating and identifying user existence and location within the region of interest based on input data from the one or more TDSM unit and data about relative arrangement of coverage zones of the transducer array units and sensing volumes of the TDSM units. It should be understood that generally an initial calibration may be performed to the system. Such initial calibration typically comprises providing data about number, mounting locations and respective coverage zones of the different transducer array units, TDSM units and microphone units, as well as any other connected elements such as speakers when used. Such calibration may be done automatically in the form of generating of 3D model as described above, or manually by providing data about arrangement of the region of interest and mounting location of the transducer array units, TDSM units and microphone units. 
     It should be noted that the one or more TDSMs may comprise one or more camera units, three dimensional camera units or any other suitable imaging system. Additionally, the one or more transducer units may also be configured to periodic scanning of the coverage zone with an ultra-sonic beam and determine mapping of the coverage region based on detected reflection. Thus, the one or more transducer units may be operated as sonar to provide additional mapping data. Such sonar based mapping data may include data about reflective properties of surfaces as well as the spatial arrangement thereof. 
     Additionally, the one or more microphone units may be configured as microphone array units and operable for providing input acoustic audible data collected from a respective collection region (e.g. sensing volume). The one or more microphone units may include an array of microphone elements enabling collection of audible data and providing data indicative of direction from which collected acoustic signals have been originated. The collected acoustic directional data may be determined based on phase or time variations between signal portions collected by different microphone elements of the array. Alternatively, the microphone unit may comprise one or more directional microphone elements configured for collecting acoustic signals from different directions within the sensing zone. In this configuration, direction to the origin of a detected signal can be determined based on variation in collected amplitudes as well as time delay and/or phase variations. 
     Generally, an audio communication session may be unilateral or bilateral. More specifically, a unilateral communication session may include an audible notification sent to a user such as notification about new email, notification that a washing machine finished a cycle etc. A bilateral audio communication session of the user generally includes an audio conversations during which audible data is both transmitted to the user and received from the user. Such communication sessions may include a telephone conversation with a third part, user initiated commands requesting the system to perform one or more tasks etc. 
     Additionally, the system may be employed in a plurality of disconnected remote regions of interest providing private communication between two or more remote spaces. To this end, as described herein below the region of interest may include one or more connected space and additional one or more disconnected/remote location enabling private and hand free communication between users regardless of physical distance between them, other than relating to possible time delay associated with transmission of data between the remote locations. 
     The technique of the present invention may also provide indication associated with unilateral communication session and about success thereof. More specifically, the present technique utilize sensory data received from one or more of the TDSMs indicating movement and/or reaction of the user at time period of receiving input notification and determine to certain probability if the user actually noticed the notification or not. Such response may be associated with facial of body movement, voice or any other response that may be detected using the input devices associated with the system. 
     As indicated above, the 3D model of the space where the system is used may include one or more non-overlapping or partially overlapping coverage regions associated with one or more transducer units. Further, the present technique allows for a user to maintain a communication session while moving about between regions. To this end, the system is configured to receive sensing data from the one or more TDSMs and for processing the sensing data to provide periodic indication about the location of one or more selected users, e.g. a user currently engaged in communication session. 
     Further, to provide private sound the one or more transducer unit are preferably configured and operated to generate audible sound within a relatively small focus point. This forms a relatively small region where the generated acoustic waves are audible, i.e. audible frequency and sufficient sound pressure level (SPL). The bright zone, or audible region, may for example be of about 30 cm radius, while outside of this zone the acoustic signals are typically sufficiently low to prevent comprehensive hearing by others. Therefore the audio communication system may be also configured for processing input sensing data to locate a selected user and identify location and orientation of the user&#39;s head and ears to determine location for generating audible (private) sound region. Based on the 3D model of the space where the system is employed, the processing may include determining a line of sight between a selected transducer unit and at least one of the user&#39;s ears. In case no direct line of sight is determined, a different transducer unit may be used. Alternatively, the 3D model of the space may be used to determine a line of sight utilizing sound reflection from one or more reflecting surfaces such as walls. When the one or more transducer units are used as sonar-like mapping device, data about acoustic reflection of the surfaces may be used to determine optimal indirect line of sight. Additionally, to provide effective acoustic performance, the present technique may utilize amplitude adjustment when transmitting acoustic signals along an indirect line of sight to a user. 
     In this regards, it should be also be noted that in cases/embodiments where the system is configured to engage with both ears of a user separately, amplitude adjustment and balancing is also carried out for balancing the volume between the two ears (specifically in cases where the ears are at different distances to the transducer units serving them). 
     In this connection, the above described technique and system enables providing audio communication within a region of interest (ROI), by employing a plurality of transducer array units and corresponding TDSM units and microphone units. The technique enables audio private communication to one or more users, for communicating between them or with external links, such that only a recipient user of certain signal receives an audible and comprehensible acoustic signal, while other users, e.g. located at distance as low as 50 cm from the recipient, will not be able to comprehensively receive the signal. 
     Also, the technique of the present invention provides for determining location of a recipient for direct and accurate transmission of the focused acoustic signal thereto. The technique also provides for periodically locating selected users, e.g. user marked as in ongoing communication session, to thereby allow the system to track the user and maintain the communication session even when the users moves in space. To this end the technique provides for continuously selecting preferred transducer array units for signal transmission to the user in accordance with user location and orientation. The system and technique thereby enable a user to move between different partially connected spaces within the ROI (e.g. rooms) while maintaining an ongoing communication session. 
     Binaural hearing ability of humans and animals enables them to locate sounds in three dimensions within an auditory space (i.e. to resolve direction and possibly also distance and distinguish between sounds arriving from different locations in the auditory space). 
     This is possible because the brain infers the direction and possibly also the distance/location of the sound source by comparing the binaural sounds sensed by the left and right ears to identify sound modifications/differences (sound cues) between the two ears that are indicative of the direction/location of the sound source. Among the sound cues included are time difference of arrival, and intensity difference due to a difference in the acoustical paths of propagation of the sound from the source to the two ears respectively, as well as spectral (frequency spectrum) modifications caused by interaction of the sounds arriving from the sound source with the head/ears anatomy, in which the original source sound is modified before it enters the ear canal for processing by the auditory system. The brain processes these modifications of the sounds captured by the two different ears to infer the direction and possibly distance of the sound source(s). 
     An illusion of three dimensional (3D) auditory space, a so-called virtual auditory space (VAS), can be generated by headphones by utilizing appropriate filtering of sounds presented over the headphones. When utilizing headphones, a head-related transfer function (HRTF) is typically used for carrying out appropriate filtering of the sounds presented over each individual one of the headphones for creating the VAS. 
     Generally the head-related transfer function (HRTF) is a response function characterizing how an ear of a user receives sound from a point in space. As indicated above, properties of the user&#39;s head and ears (e.g. size and shape and/or mechanical properties thereof), transform the sound sensed by the eardrum and thereby affect how sounds from different points in space are perceived, and particularly introduce different spectral modifications to sounds arriving to the user from different directions relative to the user. Typically, some sound frequencies (e.g. from 2-5 kHz) are amplified, while others are attenuated, while the parameters of the of the amplification/attenuation generally depend on the direction and possibly also distance of the sound source. Also as indicated above, time delay and intensity difference are introduced to sounds arriving from the same source to the left and right ears of the user, due to a difference in the acoustical path from the source to the two ears respectively. 
     A virtual auditory space (VAS) sensation can be created, for example by headphones by utilizing a couple of HRTFs for two ears of the user respectively, to synthesize binaural sound that is perceived by the user as coming from a particular direction/location in space. The HRTFs introduce spectral modifications to the sounds depending on the relative directions from which they arrive to the respective ears. The HRTF presents the spectral modifications applied by the head to sound propagating from a certain direction in free air until the sound arrives and is sensed by the eardrum of a particular ear. Moreover, typically proper relative time delays and intensity differences are also respectively introduced to the sounds transmitted to the two ears whereby the magnitude of the time delay and intensity difference depends on the different trajectories/paths (direct or indirect) of sounds from the particular direction/location of a sound source towards the respective ears. 
     Thus according to one broad aspect of the present invention, there is provided a system for use in audio communication. The system includes:
         one or more (e.g. a plurality of) transducer units to be located in a plurality of sites for covering respective coverage zones in said sites. The sites may be different spaces and/or regions of interest (ROIs) to which audio services should be provided by the system. The at transducer units (e.g. at least some of them) are capable of emitting ultra-sonic signals in one or more general frequencies for forming local audible sound field at selected spatial position within their respective coverage zones; the transducer unit may include an array of transducer elements.   one or more (e.g. a plurality of) a three dimensional sensor modules (TDSMs; also referred to herein as three dimensional input device, e.g. 3D camera, radar, sonar, LIDAR) configured to provide data about three dimensional arrangement of the surrounding within a field of view of the input device. The TDSMs are adapted to be located in the sites (spaces) to be covered by the system, and each three dimensional sensor module is configured and operable to provide sensory data about three dimensional arrangement of elements in a respective sensing volume within the sites.   a mapping module providing map data indicative of a relation between the sensing volumes and the coverage zones of said TDSMs and transducer units respectively.   a user detection module connectable to said one or more three dimensional sensor modules for receiving said sensory data therefrom, and configured and operable to process said sensory data to determine spatial location of at least one user within the sensing volumes of the TDSMs. and   an output sound generator (also referred to herein as sound processing utility) connectable to said one or more transducer units and adapted to receive sound data indicative of sound to be transmitted to said at least one user, and configured and operable for operating at least one selected transducer unit for generating localized sound field carrying said sound data in close vicinity to said at least one user, wherein said output sound generator utilizes the map data to determine said at least one selected transducer unit in accordance with said data about spatial location of the at least one user such that the respective coverage zone of said selected transducer unit includes said location of said at least one user.       

     In some embodiments the system includes an audio session manager (e.g. including input and output communication utilities) which is configured to enable communication with remote parties via one or more communication networks; and at least one sound processing utility. The at least one processor utility comprises: region of interest (ROI) mapping module configured and operable to receive three-dimensional input of the field of view from the 3D input device and generate a 3D model of the ROI; user detection module configured and operable to receive three-dimensional input of the field of view from the 3D input device and determine existence and location of one or more people within the region of interest. The processor unit is configured for generating voice data and for operating the at least one transducer unit to transmitting suitable signal for generating a local sound field at close vicinity to a selected user&#39;s ear thereby enabling private communication with the user. 
     The system may further comprise a received sound analyzer connectable to one or more microphone units configured for receiving audio input from the ROI, and adapted to determine data indicative of location of origin of said audio signal within the ROI. 
     Additionally or alternatively, the system may comprise, or be connectable to one or more speakers for providing audio output that may be heard publicly by a plurality of users. Further, the system may also comprise one or more display units configured and operable for providing display of one or more images or video to users. 
     It should be noted that the system may utilize data about user location for selection of one or more transducer units to provide local private audio data to the user. Similarly, when speakers and/or display units are used, the system may utilize data about location of one or more selected users to determine one or more selected speaker and/or display units for providing corresponding data to the users. 
     According to some embodiments the processing unit may further comprise a gesture detection module configured and operable to receive input audio signals and location thereof from the audio-input location module and to determine if said input audio signal includes one or more keywords requesting initiation of a process or communication session. 
     The processing unit may further comprise an orientation detection module. The orientation detection module may be configured and operable for receiving data about said 3D model of the region of interest and data about location of at least one user, and for determining orientation of the at least one user&#39;s ears with respect to the system thereby generating an indication whether at least one of the at least one user&#39;s ears being within line of sight with the at least one transducer unit. 
     According to some embodiments, the processor unit may further comprise a transducer selector module configured and operable for receiving data indicating whether at least one of the at least one user&#39;s head or ears being within line of sight with the at least one transducer unit and for determining optimized trajectory for sound transmission to the user&#39;s ears. The optimized trajectory may utilize at least one of: directing the local sound region at a point being within line of sight of the at least one transducer unit while being within a predetermined range from the hidden user&#39;s ear; and receiving and processing data about 3D model of the region of interest to determine a sound trajectory comprising one or more reflection from one or more walls within the region of interest towards the hidden user&#39;s ear. 
     According to some embodiments, the processing unit may be configured and operable for communicating with one or more communication systems arranged to form a continuous field of view to thereby provide continuous audio communication with a user while allowing the user to move within a predetermined space being larger than a field of view of the system. Further, the communication system may be employed within one or more disconnected regions providing seamless audio communication with one or more remote locations. 
     According to some embodiments, the processing unit may be configured and operable for providing one or more of the following communication schemes:
         managing and conducting a remote audio conversation, the processing unit is configured and operable for communication with a remote audio source through the communication network to thereby enable bilateral communication (e.g. telephone conversation);   providing vocal indication in response to one or more input alerts received from one or more associates systems through said communication network;       

     responding to one or more vocal commands from a user generate corresponding commands and transmit said corresponding commands to selected one or more associates systems through the communication network, thereby enabling vocal control for performing one or more tasks by one or more associated systems. 
     According to yet some embodiments, the processing unit may further comprise a gesture detection module configured and operable for receiving data about user location from the user detection module and identify whether one or more predetermined gestures are performed by the user, upon detecting said one or more predetermined gestures, the gesture detection module generates and transmits a corresponding command to the processing unit for performing one or more corresponding actions. 
     The system may also comprise a face recognition module configured and operable for receiving input data from the a three dimensional input device and for locating and identifying one or more users within the ROI, the system also comprises a permission selector module, the permission selector module comprises a database of identified users and list of actions said users have permission to use, the permission selector module received data about user&#39;s identity and data about a requested action by said user, and provides the processing unit data indicative to whether said user has permission for performing said requested action. 
     According to one other broad aspect of the present invention, there is provided a system for use in audio communication. The system comprising: one or more transducer units to be located in a plurality of physical locations for covering respective coverage zones, wherein said transducer units are capable of emitting ultra-sonic signals in one or more frequencies for forming local audible sound field at selected spatial position within its respective coverage zone; one or more Three Dimensional Sensor Modules (TDSM) (e.g. 3D camera, radar, sonar, LIDAR) to be located in said sites, wherein each three dimensional sensor module is configured and operable to provide sensory data about three dimensional arrangement of elements in a respective sensing volume within said sites; a mapping module providing map data indicative of a relation between the sensing volumes and the coverage zones; a user detection module connectable to said one or more three dimensional sensor modules for receiving said sensory data therefrom, and configured and operable to process said sensory data to determine spatial location of at least one user&#39;s ear within the sensing volumes of the three dimensional sensor modules; and a sound processor utility connectable to said one or more transducer units and adapted to receive sound data indicative of sound to be transmitted to said at least one user&#39;s ear, and configured and operable for operating at least one selected transducer unit for generating localized sound field carrying said sound data in close vicinity to said at least one user&#39;s ear, wherein said output sound generator utilizes the map data to determine said at least one selected transducer unit in accordance with said data about spatial location of the at least one user&#39;s ear received from the corresponding user detection module such that the respective coverage zone of said selected transducer unit includes said location of said at least one user&#39;s ear. 
     The one or more transducer units are preferably capable of emitting ultra-sonic signals in one or more frequencies for forming local focused demodulated audible sound field at selected spatial position within its respective coverage zone. 
     The system may generally comprise a received sound analyzer configured to process input audio signals received from said sites. Additionally, the system may comprise and audio-input location module adapted for processing said input audio signals to determine data indicative of location of origin of said audio signal within said sites. The received sound analyzer may be connectable to one or more microphone units operable for receiving audio input from the sites. 
     According to some embodiments the system may comprise, or be connectable to one or more speakers and/or one or more display units for providing public audio data and/or display data to users. Generally the system may utilize data about location of one or more users for selecting speakers and/or display units suitable for providing desired output data in accordance with user location. 
     According to some embodiments, the user detection module may further comprise a gesture detection module configured and operable to process input data comprising at least one of input data from said one or more TDSM and said input audio signal, to determine if said input data includes one or more triggers associated with one or more operations of the system, said sound processor utility being configured determine location of origin of the input data as initial location of the user to be associated with said operation of the system. Said one or more commands may comprise a request for initiation of an audio communication session. The input data may comprise at least one of audio input data received by the received sound analyzer and movement pattern input data received by the TDSM. More specifically, the gesture detection module may be configured for detecting vocal and/or movement gestures. 
     According to some embodiments, the user detection module may comprise an orientation detection module adapted to process said sensory data to determine a head location and orientation of said user, and thereby estimating said location of the at least one user&#39;s ear. 
     According to some embodiments, the user detection module includes a face recognition module adapted to process the sensory data to determine location of at least one ear of the user. The output sound generator is configured and operable for determining an acoustic field propagation path from at least one selected transducer unit for generating the localized sound field for the user such that the localized sound field includes a confined sound bubble in close vicinity to the at least one ear of the user. 
     For example the face recognition module may be configured and operable to determine said location of the at least one ear of the user based on an anthropometric model of the user&#39;s head. In some cases the face recognition module is configured and operable to at least one of constructing and updating said anthropometric model of the user&#39;s head based on said sensory data received from the TDSM. 
     In some embodiments, the face recognition module is adapted to process the sensory data to determine locations of two ears of the user, and wherein said output sound generator is configured and operable for determining two acoustic field propagation paths from said at least one selected transducer unit towards said two ears of the user respectively, and generating said localized sound field such that it includes two confined sound bubbles located in close vicinity to said two ears of the user respectively, thereby providing private binaural (e.g. stereophonic) audible sound to said user. 
     In some embodiments, the output sound generator is configured and operable for determining respective relative attenuations of acoustic field propagation along the two propagation paths to the two ears of the user, and equalizing volumes of the respective acoustic fields directed to the two ears of the user based on said relative attenuations, to thereby provide balanced binaural audible sound to said user. 
     According to some embodiments the user detection module is further configured and operable to process the received sensory data and to differentiate between identities of one or more users in accordance with the received sensory data, the user detection module thereby provides data indicative of spatial location and identity of one or more users within the one or more sensing volumes of the three dimensional sensor modules. 
     The system may also comprise a face recognition module. The face recognition module is typically adapted for receiving data about the user location from the user detection module, and for receiving at least a portion of the sensory data associated with said user location from the TDSMs, and is configured and operable for applying face recognition to determine data indicative of an identity of said user. In some configurations, the system may further comprise a privileges module. The privileges module may comprise or utilize a database of identified users and list of actions said users have permission to use. Generally, the privileges module receives said data indicative of the user&#39;s identity from said face recognition module and data about a requested action by said user, and provides the processing unit data indicative to whether said user has permission for performing said requested action. 
     According to some embodiments, the sound processor utility may be adapted to apply line of sight processing to said map data to determine acoustical trajectories between said transducer units respectively and said location of the user&#39;s ear, and process the acoustical trajectories to determine at least one transducer unit having an optimal trajectory for sound transmission to the user&#39;s ear, and set said at least one transducer unit as the selected transducer unit. Such optimized trajectory may be determined such that it satisfies at least one of the following: it passes along a clear line of sight between said selected transducer unit and the user&#39;s ear while not exceeding a certain first predetermined distance from the user&#39;s ear; it passes along a first line of sight from said transducer unit and an acoustic reflective element in said sites and from said acoustic reflective element to said user&#39;s ear while not exceeding a second predetermined distance. 
     According to some embodiments, sound processor utility utilizes two or more transducer units to achieve an optimized trajectory, such that at least one transducer unit has a clear line of sight to one of the user&#39;s ears and the least one other transducer unit has a clear line of sight to the second user&#39;s ear. 
     According to some embodiments, the sound processor utility may be adapted to apply said line of site processing to said map data to determine at least one transducer unit for which exist a clear line of site to said location of the user&#39;s ear within the coverage zone of the at least one transducer unit, and set said at least one transducer unit as the selected transducer unit and setting said trajectory along said line of site. 
     In case the lines of site between said transducer units and said location of the user&#39;s ear are not clear, said line of site processing may include processing the sensory data to identify an acoustic reflecting element in the vicinity of said user&#39;s; determining said selected transducer unit such that said trajectory from the selected transducer unit passes along a line of site from the selected transducer unit and said acoustic reflecting element, and therefrom along a line of site to the user&#39;s ear. 
     The output sound generator is configured and operable to monitor location of the user&#39;s ear to track changes in said location, and wherein upon detecting a change in said location, carrying out said line of site processing to update said selected transducer unit, to thereby provide continuous audio communication with a user while allowing the user to move within said sites. The sound processor utility may be adapted to process said sensory data to determine a distance along said propagation path between the selected transducer unit and said user&#39;s ear and adjust an intensity of said localized sound field generated by the selected transducer unit in accordance with said distance. In case an acoustic reflecting element exists in the trajectory between the selected transducer unit and the user&#39;s ear, said processing utility may be adapted to adjust said intensity to compensate for an estimated acoustic absorbance properties of said acoustic reflecting element. Further, in case an acoustic reflecting element exists in said propagation path, said processing utility may be adapted to equalized spectral content intensities of said ultrasonic signals in accordance with said estimated acoustic absorbance properties indicative of spectral acoustic absorbance profile of said acoustic reflecting element. 
     Generally, the sound processor utility may be adapted to process the input sensory data to determine a type (e.g. table, window, wall etc.) of said acoustic reflecting element and estimate said acoustic absorbance properties based on said type. 
     The sound processor utility may also be configured for determining a type of one or more acoustic reflective surfaces in accordance with data about surface types stored in a corresponding storage utility and accessible to said sound processor utility. 
     According to some embodiments, the system may comprise a communication system connectable to said output sound generator and configured and operable for operating said output sound generator to provide communication services to said user. The system may be configured and operable to provide one or more of the following communication schemes:
         managing and conducting a remote audio conversation, the communication system is configured and operable for communication with a remote audio source through the communication network to thereby enable bilateral communication (e.g. telephone conversation);   managing and conducting seamless local private audio communication between two or more users within the region of interest;   processing input audio data and generating corresponding output audio data to one or more selected users;   providing vocal indication in response to one or more input alerts received from one or more associates systems through said communication network; and   responding to one or more vocal commands from a user generate corresponding commands and transmit said corresponding commands to selected one or more associates systems through the communication network, thereby enabling vocal control for performing one or more tasks by one or more associated systems.       

     The system  1000  may comprises a gesture detection module  550  (which is also referred to herein interchangeably as gesture detector) configured and operable for receiving data about user location from the user detection module, and connectable to said three dimensional sensor modules for receiving therefrom at least a portion of the sensory data associated with said user location; said gesture detection is adapted to apply gesture recognition processing to said at least a portion of the sensory data to identify whether one or more predetermined gestures are performed by the user, upon detecting said one or more predetermined gestures, the gesture detection module generates and transmits a corresponding commands for operating said communication system for performing one or more corresponding actions. 
     According to some embodiments, the system may further comprise a user response detection module adapted for receiving a triggering signal from said communication system indicative of a transmission of audible content of interest to said user&#39;s ear; and wherein said user response detection module is adapted for receiving data about the user location from the user detection module, and for receiving at least a portion of the sensory data associated with said user location from the three dimensional sensor modules, and is configured and operable for processing said at least portion of the sensory data, in response to said triggering signal, to determine response data indicative of a response of said user to said audible content of interest. The response data may be recorded in a storage utility of said communication system or uploaded to a server system. 
     The system of claim may be associated with an analytics server configured and operable to receive said response data from the system in association with said content of interest and process said statistically response data provided from a plurality of users in response to said content of interest to determine parameters of user&#39;s reactions to said content of interest. 
     Generally, said content of interest may include commercial advertisements and wherein said communication system is associated with an advertisement server providing said content of interest. 
     According to one other broad aspect of the present invention, there is provided a vocal network system comprising a server unit and one or more local audio communication systems as described above arranged in a space for covering one or more ROI&#39;s in a partially overlapping manner; the server system being connected to the one or more local audio communication systems through a communication network and is configured and operable to be responsive to user generated input messages from any of the local audio communication systems, and to selectively locate a desired user within said one or more ROI&#39;s and selectively transmit vocal communication signals to said desired user in response to one or more predetermined conditions. 
     According to yet one other broad aspect of the invention, there is provided a server system for use in managing personal vocal communication network; the server system comprising: an audio session manager configured for connecting to a communication network and to one or more local audio systems; a mapping module configured and operable for receiving data about 3D models from the one or more local audio systems and generating a combined 3D map of the combined region of interest (ROI) covered by said one or more local audio systems; a user location module configured and operable for receiving data about location of one or more users from the one or more local audio systems and for determining location of a desired user in the combined ROI and corresponding local audio system having suitable line of sight with the user. The server system is configured and operable to be responsive to data indicative of one or more messages to be transmitted to a selected user. In response to such data, the server system receives, from the user location module, data about location of the user and about suitable local audio system for communicating with said user and transmitting data about said one or more messages to the corresponding local audio system for providing vocal indication to the user. 
     The user location module may be configured to periodically locate the selected user and the corresponding local audio system, and to be responsive to variation in location or orientation of the user to thereby change association with a local audio system to provide seamless and continuous vocal communication with the user. 
     According to yet another broad aspect of the invention, there is provided a method for use in audio communication, the method comprising: providing data about one or more signals to be transmitted to a selected user, providing sensing data associated with a region of interest, processing said sensing data for determining existence and location of the selected user within the region of interest, selecting one or more suitable transducer units located within the region of interest and operating the selected one or more transducer elements for transmitting acoustic signals to determined location of the user to thereby provide local audible region carrying said one or more signals to said selected user. 
     According to yet another broad aspect of the invention, there is provided a method comprising: transmitting a predetermined sound signal to a user and collecting sensory data indicative of user response to said predetermined sound signal thereby generating data indicative of said user&#39;s reaction to said predetermined sound signal, wherein said transmitting comprising generating ultra-sonic field in two or more predetermined frequency ranges configured to interact at a distance determined in accordance with physical location of said user, to thereby form a local sound field providing said predetermined sound signal. 
     According to another broad aspect of the present invention there is provided a system for use in audio communication. The system includes:
         at least one transducer unit adapted for forming local audible sound field at selected spatial position within at least one respective coverage zone of at least one site;   at least one sensor (e.g. Three Dimensional Sensor Module—TDSM) configured and operable to provide sensory data about three dimensional arrangement of elements in a respective sensing volume within the at least one site;   a user detection module connectable to the at least one sensor (e.g., to one or more TDSMs) for receiving the sensory data therefrom, and configured and operable to process the sensory data to determine spatial location of at least one user within the at least one site;   a face recognition module adapted to process the sensory data to determine location of at least one ear of the user; and   an output sound generator connectable to the one or more transducer units and adapted to receive sound data indicative of sound to be transmitted to the at least one user, and configured and operable for determining an acoustic field propagation path from said at least one transducer unit for generating a localized sound field including a confined sound bubble in close vicinity to the at least one ear of the user, and operating the at least one transducer unit for generating the localized sound field.       

     According to yet another broad aspect of the present invention there is provided a method for use in audio communication, the method includes: providing data about one or more signals to be transmitted to a selected user; providing sensing data associated with a region of interest; processing the sensing data to determine existence of the selected user within the region of interest, and to determine a location of at least one ear of the user in the region of interest; and selecting and operating one or more suitable transducer units located within the region of interest for transmitting acoustic signals to the determined location of the at least one ear of the user. 
     In some implementations the location of the at least one ear of the user is determined based on an anthropometric model of the user&#39;s head. In some cases, the anthropometric model is constructed and/or updated based on the sensing data. 
     In some embodiments the method/system are configured and operable for: processing the sensing data to determine locations of two ears of the user; determining two acoustic field propagation paths from the selected one or more transducer units towards the two ears of the user respectively; and operating the selected transducer unit(s) for transmitting acoustic signals to the determined locations of the two ears along the two respective acoustic field propagation paths. In some cases, the method further includes determining respective relative attenuations of acoustic field propagation along the two propagation paths to the two ears of the user, and equalizing volumes of the respective acoustic fields directed to the two ears of the user based on the relative attenuations, to thereby provide balanced binaural audible sound to the user. 
     According to another board aspect of the present invention there is provided a method for producing virtual binaural audio space, the method comprising: 
     (a) providing staged audio data indicative of at least one audio data piece and a position of a virtual source of said audio data piece relative to a listener; 
     (b) determining a head positioning data indicative of location and orientation of a user&#39;s head, whereby the user is designated to be said listener of the audio data; 
     (c) transmitting one or more ultrasound fields towards a one or more selected audio center points located in the vicinity of the user&#39;s head for producing, via sound from ultrasound effect, left and right audible sound fields with said at least one audio data piece at respective left and right ears of said user, and, 
     (d) based on said position of the virtual source and said head positioning data, controlling at least one parameter of said one or more ultrasound fields such that a difference between said respective left and right audible sound fields is perceived by the user as an audible sound field propagating to said user from said position of the virtual source and carrying said at least one audio data piece. 
     In some embodiments, the determining of the head positioning data comprises monitoring the user&#39;s head position to determine head positioning data indicative of at least a location of said user&#39;s head, and determining one or more selected audio center points in accordance with the position of said virtual source and the location of said user&#39;s head. For example, the one or more ultrasound fields are produced by one or more transducer systems; wherein said head positioning data is further indicative of an orientation of the user&#39;s head; and wherein said head positioning is processed to determine one or more relative locations and orientations of the user&#39;s head with respect to said one or more transducer systems, to select at least one of said transducer systems for projecting said one or more ultrasound fields to said one or more selected audio centers. 
     In some embodiments, the position data of said virtual source relative to the listener is indicative of azimuth and elevation data of the virtual source relative to said user&#39;s head; said one or more selected audio center points comprise a single audio center point located within a perimeter region surrounding said user&#39;s head by a distance not exceeding 30 centimeters from the head; and wherein said controlling of the at least one parameter of said ultrasound fields comprises utilizing the azimuth and elevation data of the virtual source relative to the user&#39;s head to determine a position of said single audio center point within said perimeter region such that acoustic interactions of said left and right audible sound fields with the user&#39;s head mimics a head related transfer function (HRTF) of said head from the position of the virtual source. Typically, a nominal azimuth and nominal elevation of said single audio center point relative to said user&#39;s head matches said azimuth and elevation of the virtual source relative to the user&#39;s head. 
     The position of the single audio center point may be maintained fixed under changes in an orientation of said user&#39;s head to thereby provide that said virtual source is perceived by the user to be at a fixed position relative to the user. 
     In some embodiments, the position data of said virtual source relative to the listener is indicative of azimuth and elevation data of the virtual source relative to said user&#39;s head. The controlling of the at least one parameter of said ultrasound fields may comprise:
         a. in case the azimuth of said virtual source is within a certain angular range of relative to a symmetry plane of said user&#39;s head, selecting said one or more audio center points to includes a single audio center point located at said azimuth relative to the head and within a perimeter region that surrounds said user&#39;s head by a distance not exceeding 30 centimeters from the head, such that interaction of said left and right audible sound fields with the user&#39;s head during their propagation from said single audio center point towards the left and right ears of the user respectively mimics a head related transfer function (HRTF) effect of the head on sounds arriving the azimuth of the virtual source; and   b. in case the azimuth of said virtual source exceeds said certain angular range, the method includes selecting said one or more audio center points to include at least two audio center points within said perimeter, and transmitting at least two ultrasound fields towards said at least two audio center points for separately producing said left and right audible sound fields.       

     In some embodiments, the one or more ultrasound fields comprise left and right ultrasound fields transmitted towards respective left and right audio center points located in the vicinity of said user&#39;s left and right ears, for separately producing said left and right audible sound fields at said user&#39;s left and right ears. The head positioning may be processed to determine one or more relative locations and orientations of the user&#39;s head with respect to said one or more transducer systems, to select at least one of said transducer systems for use as a left transducer system for projecting sound field to a left ear of the user, and selecting at least one of said transducer systems as a right transducer system for projecting sound field to a right ear of the user, said selected left and right transducer systems being the same or different transducer systems from said one or more transducer systems. The intensities of the one or more ultrasound fields may be selected such that said audible sound fields are above auditory level only within a maximal radius not exceeding a range of 25-50 CM from said left and right audio center points, thereby providing private virtual binaural audio space to said user. 
     The controlling of the at least one parameter may comprise adjusting a time delay between the left and right ultrasound fields in accordance with a difference between a distance of said virtual source to said left and right ears, respectively. 
     The controlling of the at least one parameter may comprise utilizing a head related transfer function (HRTF) for applying spectral adjustment to frequency contents of said left and right ultrasound fields, respectively, in accordance with a position of said virtual source relative to said user&#39;s head. 
     The controlling of the at least one parameter of said left and right ultrasound fields may comprise utilizing azimuth and elevation data of the virtual source relative to the user&#39;s head to shift said left and right audio center points, respectively, relative to left and right locations of the left and right ears of the user such that acoustic interactions of said left and right audible sound fields with the user&#39;s head at least partially mimics a head related transfer function (HRTF) of said head from the position of the virtual source. The intensities of said left and right ultrasound fields may be selected such that said respective left and right audible sound fields are above auditory level within a radius R not exceeding a range of 50 cm from said left and right audio center points, respectively, and wherein the shifted left and right audio center points are spaced from left and right locations of the left and right ears, respectively, by a distance not exceeding said radius R. 
     In some embodiments, the one or more transducer systems are phased array ultrasound transducers, and wherein the method further comprises carrying out the following per each ultrasound field of said one or more ultrasound fields which is to be generated at a respective audio center point: 
     assigning an ultrasound transducer system of said one or more transducer systems to said ultrasound field, based on locations of said one or more transducers systems relative to the audio center point of said ultrasound field and based on the location of the head; 
     processing said at least one audio data piece based on the relative position between the assigned transducer system and the audio center point of said ultrasound field for generating a corresponding transducer channel adapted for operating the assigned transducer system, for generating the respective ultrasound field such that frequency contents of the ultrasound field generates the respective audible sound field with said at least one audio data piece via sound from ultrasound; 
     applying beam forming to transducer channel to produce beam-formed channel for operating phase arrays of assigned transducers to generate a respective ultrasound beams directed to the audio center point of said ultrasound field. 
     In some embodiments, the generating of the corresponding transducer channel comprises utilizing the audio data piece for determining frequency content of one or more ultrasound beams to be transmitted by the assigned transducer system towards said audio center point, wherein at least one of said ultrasound beams is an audio modulated ultrasound beam, whose frequency contents include at least two ultrasonic frequency components selected to produce said audible sound after undergoing non-linear interaction in a non-linear medium; and 
     said beam forming of the transducer channel comprises:
         determining one or more distinct respective focal points for one or more ultrasound beams; and   processing the frequency content of the one or more ultrasound beams to form a beam-formed ultrasound channel comprising a set of phase shifted signals adapted for actuating elements of the respective phased array ultrasound transducers for generation of said one or more ultrasound beams focused on said distinct focal points.       

     The invention also provides an alerting method for use in producing audible alerts to a vehicle driver, the alerting method comprising: monitoring a vehicle environment and upon identifying at least one hazard/event, carrying out the method of any one of the preceding claims, comprising generating said staged audio data such that said at least one audio data piece is indicative of said at least one identified hazard/event and said position of the virtual source corresponds to a position of said identified at least one hazard/event relative to a driver location in the vehicle. 
     The invention also provides a system for producing virtual binaural audio space, the system comprising: 
     (a) an audio session manager configured and operable to provide staged audio data indicative of at least one audio data piece and a position of a virtual source of said audio data piece relative to a listener; 
     (b) a head positioning module configured and operable to determine head positioning data indicative of location and orientation of a user&#39;s head, whereby the user is designated to be said listener of the audio data; 
     (c) a binaural ultrasound fields manager configured and operable for generating signals of one or more ultrasound channels signals to be provided to one or more ultrasound transducers for transmitting one or more respective ultrasound fields towards one or more audio center points, to thereby produce, via sound from ultrasound effect, audible sound fields at said audio center points carrying said at least one audio data piece points and propagating from said audio center points towards left and right ears of said user to affect left and right audible sound fields perceived by said left and right ears of said user; and 
     wherein said binaural ultrasound fields manager is configured and operable for controlling at least one parameter of the ultrasound channels to adjust in accordance with the position of the virtual source and the head positioning data in order to affect a difference between said respective left and right audible sound fields such that the left and right audible sound fields are perceived by the user as an audible sound field propagating to said user from the direction of the virtual source and carrying said at least one audio data piece; 
     (d) an output sound from ultrasound generator module configured and operable to process the one or more ultrasound channels for generating beam formed ultrasound channels for operating said transducers to transmit one or more ultrasound fields towards the one or more selected audio center points. 
     The head positioning module is connectable to one or more sensing modules for receiving therefrom sensing data indicative of said user; and wherein the head detection module determining of the head positioning data comprises monitoring the head positioning module comprising a pattern recognition system adapted to process said sensing data to detect said user&#39;s head and determine head positioning data indicative of a location and orientation of the user&#39;s head relative to said one or more ultrasound transducer systems. 
     The binaural ultrasound fields&#39; manager may be configured and operable to control the locations of said one or more selected audio center points in accordance with the position of said virtual source relative to the location of said user&#39;s head. The binaural ultrasound fields manager may control the locations of said one or more selected audio center points irrespective of an orientation of said head relative to the virtual source. The head positioning module may determine said position data indicative of azimuth and elevation of the virtual source relative to said user&#39;s head; said binaural ultrasound fields manager utilizes the azimuth and elevation of the virtual source relative to select said one or more selected audio center points and control their locations such that: 
     (a) the one or more selected audio center points are located within perimeter region surrounding said user&#39;s head by a distance not exceeding 30 cm from the head; and 
     (b) wherein respective locations of the audio center points within said perimeter region are adjusted such that audible sound fields, generated via sound from ultrasound effect at said audio center points, undergo acoustic interactions with the user&#39;s head to from said left and right audible sound fields at the user&#39;s ears, whereby said acoustic interaction mimics a head related transfer function (HRTF) applied by the user&#39;s head to sounds arriving thereto from the direction of the virtual source. 
     The binaural ultrasound fields manager may select said audio center points to include a single audio center point located within said perimeter region at a nominal azimuth and elevation matching the azimuth and elevation of the virtual source relative to the head. 
     The binaural ultrasound fields manager may be configured to maintain the position of the single audio center point fixed under changes in an orientation of said user&#39;s head to thereby provide that said virtual source is perceived by the user to be at a fixed position relative to the user. 
     In some embodiments, the system operates as follows:
         in case the azimuth of said virtual source is within a certain angular range of relative to a symmetry plane of said user&#39;s head, said binaural ultrasound fields manager selects said audio center points to include a single audio center point located at said azimuth relative to the head and within a perimeter region that surrounding said user&#39;s head by a distance not exceeding 30 cm from the head, such that interaction of said left and right audible sound fields with the user&#39;s head during their propagation from said single audio center point towards the left and right ears of the user respectively mimics a head related transfer function (HRTF) effect of the head on sounds arriving from the azimuth of the virtual source; and   in case the azimuth of said virtual source exceeds said angular range, the binaural ultrasound fields manager selects said audio center points to include at least two audio center point within said perimeter for respectively transmitting at least two ultrasound fields towards said at least two audio center point to separately produce said left and right audible sound fields, via sound from ultrasound effect occurring at the at least two audio center points; and said binaural ultrasound fields manager utilizing an ultrasound head related transfer function (US-HRTF) for applying spectral adjustment to frequency contents of at least two ultrasound fields such that the left and right audible sound fields are perceived by the user as audible sound arriving from the direction of the virtual source.       

     The binaural ultrasound fields manager may select said audio center points to include at least left audio center point in the vicinity of said user&#39;s left and right ears, for respectively transmitting at least two ultrasound fields towards said at least left and right audio center points to separately produce said left and right audible sound fields, via sound from ultrasound effect occurring at the left and right audio center points; and 
     wherein said binaural ultrasound fields manager controlling said at least one parameter of said transducer channels&#39; signals comprises utilizing an ultrasound head related transfer function (US-HRTF) in accordance with a direction of said virtual source relative to said user&#39;s head, thereby applying spectral adjustment to frequency contents of at least two ultrasound fields, such that the left and right audible sound fields are perceived by the user as audible sound arriving from the direction of the virtual source. 
     The system may comprise a transducer selector module configured and operable for processing the head positioning data to determine one or more relative locations and orientations of the user&#39;s head with respect to said one or more transducer systems, and thereby selecting one or more selected transducer systems of said one or more transducer systems for projecting said ultrasound fields to said audio center points. 
     The binaural ultrasound fields manager may be configured and operable to adjust intensities of said one or more ultrasound fields such that said audible sound fields generated therefrom are above auditory level only within a maximal radius not exceeding a range of 25-50 CM from said audio center points, thereby providing private virtual binaural audio space to said user. 
     Also, in some embodiments, the binaural ultrasound fields manager is configured and operable for controlling said at least one parameter by carrying out one or more of the following:
         processing the at least one audio data piece based to generate one or more ultrasound channels each comprising signals for generating an ultrasound field whereby a frequency content of the ultrasound field is adapted for generating a respective audible sound field corresponding to said at least one audio data piece via sound from ultrasound effect;   adjusting a time delay between the ultrasound channels in accordance with the position of said virtual source relative to the head;   utilizing an ultrasound head related transfer function (US-HRTF) for applying spectral adjustment to frequency content of the ultrasound channels, respectively, whereby said US-HRTF is tuned in accordance with a position of said virtual source relative to said user&#39;s head;   utilizing azimuth and elevation data of the virtual source relative to the user&#39;s head to set said one or more of the audio center points, relative to locations of left and right ears of the user, such that acoustic interactions of said left and right audible sound fields with the user&#39;s head at least partially mimics a head related transfer function (HRTF) of said head from the position of the virtual source.       

     The system may comprise a localized sound from US beam generator adapted for processing each ultrasound channel of the ultrasound channels to generate data indicative of one or more of ultrasound beams to be transmitted by one or more of the transducer systems towards the audio center point corresponding to the ultrasound channels, wherein at least one of said ultrasound beams is an audio modulated ultrasound beam, whose frequency content includes at least two ultrasonic frequency components selected to produce said audible sound after undergoing non-linear interaction in a non-linear medium, and determining one or more distinct respective focal points for said one or more ultrasound beams in the vicinity of said audio center point for causing destructive interference between said one or more beams at one or more regions surrounding said audio center point to thereby form confined localized audible sound field in the vicinity of said audio center point. 
     The one or more transducer systems may be configured as phased array ultrasound transducers, and the system may comprise a beam forming module adapted for processing the data indicative of one or more of ultrasound beams to generate a beam-formed ultrasound channel comprising a set of phase shifted signals adapted for actuating elements of the phased array ultrasound transducers for generating said one or more ultrasound beams focused on said distinct focal points. 
     The invention also provides an alerting system comprising the above-described system for producing virtual binaural audio, and a hazard notification monitor configured and operable for monitoring a vehicle environment and upon identifying at least one event of interest (e.g. hazard) in the vehicle environment, generating said staged audio data such that said at least one audio data piece is indicative of said at least one identified event of interest and said position of the virtual source corresponds to a position of said identified at least one event of interest relative to a driver location in the vehicle. 
     In another broad aspect the present invention provides conversational AI systems and methods for enabling conversational AI systems to conduct rich interactions with users. 
     Conventional conversational AI technologies generally utilize amplified speakers to provide feedback to users. This approach however lacks privacy and limits the type of feedback to of the conventional conversational AI technologies audio only. —further reducing the capacity for rich interactions. 
     The technique of the present invention facilitates selective or automated public or private communication with users of the conversational AI systems, while enabling private or public provision of audible sound to the user. Furthermore, the technique of the present invention facilitates determining the state of the user of the conversational AI (e.g. the user&#39;s pose, emotional state or other characteristics, such as gender, age group, skin color, etc.) thereby enable both efficient and rich interactions with the user. In some implementations of the invention the system determines feedback actions to be provided to the user, based on such properties as the user&#39;s (e.g. the a user&#39;s pose, facial expression) as well in relation to gestures (physical or vocal/verbal) of the user. Once determined, the feedback actions can then be rendered to the user using a combination of spatially localized audio, public audio, haptic feedback and other modalities including visual feedback. 
     Thus, according to further yet another broad aspect of the present invention, there is provided an audio communication system. The audio communication system includes the following:
         (a) one or more transducers to be located in one or more sites and capable of forming audible sound fields within respective coverage zones thereof;   (b) one or more sensors to be located in the one or more sites and configured and operable to provide sensory data about respective sensing volumes within the sites;   (c) a user detector connectable to the one or more sensors for receiving the sensory data therefrom, and configured and operable to apply recognition processing to said sensory data to identify at least one user within the sensing volumes; said user detector comprises:
           i) a user recognition module capable of processing the sensory data to identify said user within the sensing volumes (e.g. the user recognition module may be for example adapted to apply user recognition and/or face recognition);   ii) a received sound analyzer configured to process input audio signals received from said sites to determine data indicative of received sound originating from the user;   
           (d) a gesture detector configured and operable to carry out gesture recognition processing according to at least one of the following to thereby identify one or more vocal or non-vocal gestures of the user:
           a. apply the gesture recognition processing to at least a part of said sensory data associated with a spatial location of the at least one user, to identify a non-vocal gesture made by said user;   b. apply the gesture recognition processing to at least the sound originating from the user, to identify a vocal gesture made by the user;   
           (e) an audio session manager configured and operable to provide communication services to the user; the audio session manager being connectable to the gesture detector and configured and operable for processing the vocal and/or non-vocal gestures to determine one or more actions, being gesture responsive actions, to be performed by the audio communication system in response to the vocal or non-vocal gestures. In this connection the audio session manager is adapted to determine sound data for transmission to the user in association with the one or more actions; and   (f) an output sound generator connectable to said one or more transducers and adapted to receive sound data indicative to be transmitted to said at least one user, and configured and operable for operating at least one selected transducer of said transducers for transmission of the sound data to said user.       

     According to some embodiments, one or more of the transducers are capable of emitting ultra-sonic signals in one or more frequencies, and capable of directing and/or focusing the ultra-sonic signals at a spatial position within their respective coverage zone for forming local audible sound field near said spatial position. Accordingly, the output sound generator may be capable of operating the at least one selected transducer for generating localized sound field carrying the sound data to a selected spatial position being in close vicinity to the user. For instance, the system may include a mapping module providing map data indicative of a relation between the sensing volumes and the coverage zones of said sensors and transducers. The output sound generator utilizes the map data to determine the at least one selected transducer in accordance with the data about spatial location of the user such that the respective coverage zone of the selected transducer unit includes said location of said at least one user. 
     Alternatively, or additionally, in some embodiments the one or more of the transducers are capable of emitting sound signals in the audible frequency regime to thereby generate conventional audio at their respective coverage zones. 
     According to some embodiments, the audio session manager of the system is adapted to determine a type of privacy for said transmission of the sound data. The type of privacy being indicative of whether the transmission is to be conducted as:
         (i) private transmission of ultrasound signals by which local audible sound field with said sound data is formed in close vicinity of the user; or   (ii) public transmission audible sound signals with the sound data at a region of the user; and
 
In such embodiments the output sound generator is adapted to receive data indicative of the type of privacy of the transmission, and selectively operate the at least one selected transducer for the transmission of the sound data according to the privacy type.
       

     According to some embodiments the audio session manager includes a user response detector connectable for receiving pattern recognition data from the user/face recognition module and from the received sound analyzer. The user response detector is adapted for processing said data to determine and monitor a user-state of the identified user. For instance, the user-state of the identified user may include:
         intrinsic user state comprising data indicative of the user&#39;s activity (sleeping, awake, working, dancing, cooking, playing, sport, etc); and/or   extrinsic user state comprising data indicative of the contextual environment at which the user&#39;s activity takes place (alone or with other persons/public, being in local or remote social engagement, environmental conditions including audible sounds to which the user is exposed, the location of the user etc′).       

     To this end, according to some embodiments, the audio session manager is configured and operable for autonomously determine one or more actions, being autonomous actions, to be performed by the audio communication system in response to at least one of the intrinsic and extrinsic properties of the monitored user-state. For instance, the autonomous actions may include one or more of the following:
         activation of private or public notification or alert;   activation of user authentication.
 
In this connection it should be noted that the activation of the notification or alert may be associated with any one of the following extrinsic properties of the user state:
   detection of intrusion to a private space of the user (e.g. home or car intrusion);   lapse of preset time schedule (such as cooking time or wakeup time);
 
In some implementations the private or public activation is determined based on a present policy associated with said notification or alert.
       

     It should be noted that according to some embodiments the gestures detected by the system may include one or more of the following:
         one or more gestures indicating the user request for the system to transfer from public to private communication mode and vice versa;   one or more gestures presenting a user request for specific content to be presented to him in audio, visual or haptic forms;   one or more gestures presenting a user request for present of scheduled notifications/alarms by the system;   one or more gestures presenting a user request for autonomous presentation of one or more types of entertainment content by the system.       

     As indicated above, according to some embodiments the audio session manager is adapted to determine a type of privacy for required for performing the one or more actions. Based on that type of privacy, the audio session manager selectively operates one or more means to implement the required actions. The one or more means may include for example one or more of the following: 
     (a) private means comprising:
         (i) private transmission of ultrasound signals by said one or more transducers to form local audible sound field with said sound data is formed in close vicinity of said user;   (ii) provision of haptic feedback to said user;   (iii) provision of display content to said user via a private display device connectable to the system; (e.g. the private display device may be virtual or augmented eyewear display, or a display of personal user device which is defined as private)       

     (b) public means comprising:
         (i) public transmission audible sound signals by the one or more transducers to form with the sound data at a region of the user;   (ii) provision of display content via a display device (e.g. a TV or other public display) connectable to the system;   (iii) initiation of alarm via an alarm system connectable to the system;       

     It should be noted that in some implementations the provision of haptic feedback to the user may conducted by carrying out at least one of the following:
         operating the one or more transducers for generating the haptic feedback. In this case one or more of the transducers should be configured and operable for generating haptic feedback;   operating a personal user device (mobile-phone, smart-watch, etc′) connectable to the system and having a haptic feedback functionality.       

     According to yet another broad aspect of the present invention there is provided a method for audio communication. The method includes:
         obtaining spatial sensory data from one or more sensors (e.g. optical/lidar/sonar sensors) located at one or more sites;   obtaining input audio signals from one or more microphones located at the one or more sites;   applying pattern recognition to identify at least one user within the sites. the pattern recognition processing may include:
           application of user (or face) recognition to the sensory data to identify the user within the sites and determine user state properties thereof (including one or more of the following: user&#39;s position, movement, pose, expression etc′);   processing of the input audio signals received from the sites to distinguish between received sounds originating from the user and sounds to which the user is exposed, and determining data indicative of the user&#39;s speech by applying speech recognition to at least parts of the sounds originating from the user;   
           applying gesture recognition processing to the user state properties and to the user speech data to identify one or more vocal or non-vocal gestures of the user;   processing the vocal and/or the non-vocal gestures to determine one or more actions, being gesture responsive actions, to be performed in response to the vocal or non-vocal gestures.       

     In implementations/cases where at least one of the gesture responsive actions includes transmission of sound data to said user, the method may also include:
         determining a type of privacy for the transmission of the sound data. The type of privacy being indicative of whether the transmission is to be conducted as:
           (i) private transmission of ultrasound signals by which local audible sound field with the sound data is formed in close vicinity of the user; or   (ii) public transmission audible sound signals with the sound data at a region of the user; and   
           operating an output sound generator to selectively operating at least one selected transducer at a location of the identified user for the transmission of the sound data to the user with the transmission being conducted as private or public transmission according to said determined type of privacy.       

     According to some embodiments the method further includes operating an artificial intelligence to process at least one of the user state properties, the user speech data, and gestures, of said user. The operated artificial intelligence may be used to determine the sound data to be transmitted to the user. 
     According to some embodiments the method further includes:
         utilizing the user/face recognition and the processing of the sounds to which the user is exposed, to determine and monitor a user-state of the identified user. As indicated above the user-state of the identified user may include:
           intrinsic user state comprising data indicative of the user&#39;s activity; and   extrinsic user state comprising data indicative of the contextual environment at which the user&#39;s activity takes place; and   
           operating an artificial intelligence to autonomously determining one or more actions to be performed by the audio communication system in response to at least one of the intrinsic and extrinsic properties of the monitored user-state.       

     Thus, the present invention provides an audio communication systems and methods, which are capable of being implemented as, or in conjunction with, conversational AI system(s). The system of the invention may include:
         a. one or more audio sensors   b. one or more visual/spatial sensors   c. transducers or arrays thereof capable of serving as spatially localized audio feedback system;   d. pattern recognition techniques for processing the sensor inputs to determine physical gestures, spoken user data, as well as user pose, video and other sensed data; and   e. Artificial intelligence techniques of implementing conversational AI capable of determining and providing private (or spatially localized) or public actions to the user, in response to the results of the pattern recognition.       

     As will be appreciated from the below detailed description, in some implementations the technique of the present invention also provides support for haptic feedback; utilizes the processing ambient audio and user state estimation; employs biometric/emotional state estimation based on audio/video data; and utilizes cloud connection to enable incorporation of additional services and AI agents&#39; capabilities. 
     As described, will be appreciated by those versed in the art, the system of the present invention may be implemented as a home/office-based system and/or it may be integrated into a vehicle (e.g. a part of the human machine interface thereof). In the latter configuration, the system can be implemented to provide driver and passenger specific feedback to spoken requests and/or to system estimates of user state. The system may also be integrated with, or connectable to, secondary sensors such as from a home security system, in order to enhance user state estimation accuracy. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
         FIGS. 1A to 1D  schematically illustrate an audio communication system according to some embodiments of the invention, whereby  FIG. 1A  is a block diagram of the audio communication system,  FIG. 1B  schematically exemplifies deployment of the audio communication system,  FIG. 1C  shows a block diagram of an end unit of the audio communication system, and  FIG. 1D  is a block diagram of the audio communication system according to an embodiment of the invention; 
         FIG. 2  illustrates an additional example of audio communication system according some embodiments of the present invention, utilizing central control unit; 
         FIG. 3  exemplifies an end unit for private communication, suitable for use in the audio communication system according to some embodiments of the invention; 
         FIG. 4A  is a flow chart showing a method carried out according to an embodiment of the present invention for transmitting localized (confined) sound field towards a user. 
         FIGS. 4B and 4C  are schematic illustrations of a localized (confined) sound field generated in the vicinity of the user&#39;s head and ears respectively; 
         FIG. 4D  is a flow chart of a method for determining the location of the user&#39;s ears according to an embodiment of the present invention; 
         FIG. 5  exemplifies employment of an audio communication system according to some embodiments of the invention in a region of interest; 
         FIG. 6  schematically illustrates an audio communication server/control unit according to some embodiments of the present invention; 
         FIG. 7  exemplifies a method of operation for transmitting acoustic signals to a user according to some embodiments of the invention; 
         FIG. 8  exemplifies a method of operation for maintaining ongoing communication for moving user according to some embodiments of the invention; 
         FIG. 9  exemplifies a method of operation for responding to user initiated requests according to some embodiments of the present invention; and 
         FIG. 10  exemplifies a method of operation for determining user response to transmitted acoustic signal according to some embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     As indicated above, the present invention provides a system and method for providing private and hand-free audible communication within a space. Reference is made together to  FIGS. 1A to 1D , whereby  FIG. 1A to 1D , whereby  FIGS. 1A and 1D  are block diagrams of an audio communication system  1000  according to embodiments of the present invention,  FIG. 1B  schematically illustrates an exemplary deployment of the audio communication system  1000  and  FIG. 1C  is a block diagram exemplifying the configuration of an end unit  200  of the audio communication system  1000  according to some embodiments of the invention. 
     System  1000  includes one or more acoustic/sound transducers units  100 , each may typically include an array of sound transuding elements which can be operated for generating and directing directive sound beam(s) towards selected directions. For instance, transducer array units  100   a  and optional  100   b  to  100   n  are exemplified in the figure). The transducer array units  100   a - 100   n  may each be in charge of a specific region/area which is in the line of sight of the respective transducer unit. Additionally, the audio communication system  1000  also includes one or more sensors  110  (i.e. also referred to herein as spatial sensors e.g. including for example optical/camera sensors in the visible or other wavelengths) capable of providing sensing data (optical/visual and/or depth sensing data) indicative of spatial or three dimensional, arrangements/locations of objects/structures of/in the environment/sensing-volumes covered by the respective spatial sensors  110 . For instance the spatial sensors  110 , which are also referred to herein without loss of generality as three dimensional sensing devices/module (TDSM), may for example include passive and/or active sensors, such as one or more cameras (e.g. operating in the visual and/or IR wavebands), and/or depth sensors (e.g. LIDARs and/or structured light scanners), and/or echo location sensors (e.g. sonar), and/or any combination of sensors as may be known in the art, which are capable of sensing the 3D structure of the environment and provided sensory data indicative thereof. It should be noted that in some cases the spatial sensors  110  (TDSM modules) are configured to utilize/operate the transducer units  100  also as sonar modules for sensing the 3D structure of the environment. In this case, the transducer units  100  may be adapted to operate in both transmission and reception modes of ultra-sonic signals, and/or the audio input sensors  120  and/or other sensors associated with the TDSM modules  110  may be configured and operable in the ultra-sonic wavelength(s) for sensing/receiving the reflected/returned sonar signals. 
     In the present example the TDSM(s)  110  include TDSM unit  110   a  and optionally additional TDSM units  110   b  to  110   m  whereby each of the TDSM units is capable of monitoring the 3D structure of an area of a given size and shape. Accordingly, at each space/site (e.g. room/office/vehicle space) to be serviced by the audio communication system  1000 , at least one TDSM  100  and possibly more than one TDSM  100  is installed in order to cover the main regions of that space and provide the system  1000  with 3D sensory data indicative of the structure of that space. Additionally, the system includes a control system  500  (also referred to herein as local audio system) that is connectable to the TDSM(s)  110  and to the transducer unites  100  and configured and operable to receive from the TDSM(s)  110  3D sensory data indicative of the 3D structure of one or more spaces at which the TDSM(s)  110  are located/furnished, and operate the transducer unites  100  located at these spaces so as to provide designated audio data/signals to users in these spaces. 
     According, to some embodiments of the present invention the control system  500  includes a user detection module  520  (also referred to interchangeable herein as user detector) connectable to one or more of the TDSM(s)  110  (e.g. via wired or wireless connection) and configured and operable for processing the 3D sensory data obtained therefrom to detect, track and possibly also identify user(s) located in the space(s), at which the TDSM(s)  110  are installed. To this end, the user detection module  520  is configured and operable to process the sensory data to determine spatial location elements within the space(s)/sensory-volume(s) covered by the TDSM(s), and in particular detect the location of at least one of a user&#39;s head or a user&#39;s ear within the sensing volumes of the three dimensional sensor modules. 
     Generally, the TDSM(s)  110  may be located separately from the transducers  100  and/or may be associated with respective sensing coordinate systems (with respect to which the 3D sensing data of the sensing volumes sensed thereby is provided). 
     Indeed, as shown for Example in  FIG. 1B , the sensing coordinate systems may be different from the coordinate systems of the acoustic transducers  100 . For example in  FIG. 1B  the coordinate system C of the TDSM  110   b  in room R 2  is shown to be different than the coordinate system C′ of the transducer unit  100   b  covering that room. Accordingly the TDSM  110   b  can detect/sense the location of the user P (e.g. its head/ears) which is located within the sensing volume SVb and provide data indicative of the user&#39;s head/ear(s) location relative to the coordinate system C of the TDSM  110   b . The transducer  100   b  may be arranged in the room at a different location and/or at different orientation and may generally be configured to operate relative to a different coordinate system C′ for directing sound to the user P located at the transducer&#39;s  100   b  coverage zone CZb. 
     Therefore, according to some embodiments of the present invention, in order to bridge between the different coordinate systems of the TDSM(s)  110  and the transducers  100 , which may be installed at possibly different locations and/or orientations, the control system  500  includes a mapping module  510 , which is configured and operable for mapping between the coordinate systems of the TDSM(s)  110  with respect to which the sensory data is obtained, and the coordinate systems of the transducers  100  with respect to which sound is generated by the system  1000 . For instance, the mapping module  510  may include/store mapping data  512  (e.g. a list of one or more coordinate transformations, such as C to C′ transformation), which maps between the coordinates of one or more TDSM(s)  110  to the coordinates of one or more corresponding transducers  100  that pertain-to/cover the same/common space that is sensed by the corresponding TDSMs  110 . 
     Optionally the mapping module  510  also includes a calibration module  514  which is configured and operable for obtaining the mapping data between the TDSMs  110  and the transducers  100 . This is discussed in more details below. 
     Additionally, the control system  500  includes an output sound generator module  600  (also referred to interchangeably hereinbelow as sound processing utility/module). The output sound generator module  600  (the sound processing utility) is connectable to the one or more transducer units  100  and is adapted to operate the one or more transducer units  100  to generate acoustic signals to be received/heard by one or more of the users detected by the user detection module  520 . 
     To this end, the output sound generator module  600  may be associated with an audio input module  610  (e.g. external audio source) of an audio session manager  570  of the system  1000 . The audio input module  610  is configured and operable for receiving and providing the output sound generator module  600  with sound data to be transmitted to at least one predetermined user of interest (e.g. user P) in the spaces (e.g. the apartment APT) covered by the system. 
     According to some embodiments the output sound generator module  600  includes a transducer selector module  620  configured and operable for selecting the at least one selected transducer (e.g.  100   a ) out of the transducers  100 , which is suitable (best suited) for generating and directing a sound field to be heard by the predetermined user (e.g. by user P). 
     To this end, according to some embodiments the output sound generator module  600  is connected to the user detection module  520  for receiving therefrom data indicative of the location(s) of the user(s) of interest to be serviced thereby (e.g. the locations may be specified in terms of the coordinate systems C of at least one of the TDSM(s)  110 ). The output sound generator module  600  is connected to the mapping module  510  and is adapted for receiving therefrom mapping data  512  indicative of the coordinate mapping (e.g. transformation(s)) between the coordinate system of the TDSM(s)  110  sensing the user of interest P (e.g. coordinates C of TDSM  110   b ) and the coordinate system of one or more of the transducers  100  (e.g. coordinates C′ of transducer  100   b ). 
     The transducer selector receives the location of the predetermined user from the user detection module  520  (the location may be for example in terms of the respective sensing coordinate system of the TDSM (e.g.  110   b ) detecting the user P. The transducer selector module  620  is configured and operable for utilizing the mapping data obtained from the mapping module  510  (e.g. coordinate transformation C-C′ and/or C-C″) for converting the location of the head/ears of the detected user P into the coordinate spaces/systems of one or more of the transducers  100 . Optionally, the transducer selector module  620  may be adapted to also receive data indicative of structures/objects OBJ (e.g. elements such as walls and/or furniture and/or surfaces thereof) located in the vicinity of the user of interest P (e.g. in the same space/room as the user P shown in  FIG. 1B ). Then, the transducer selector module  620  utilizes the mapping data obtained from the mapping module  510  (e.g. coordinate transformation C-C′ and/or C-C″) for converting the location and possibly also the orientation of the head/ears of the detected user P into the coordinate spaces/systems of one or more relevant transducers  100 . The relevant transducers being for that matter, transducers within which coverage zones the user P is located (to this end excluded are the transducers which are not in the same space and/or which coverage zones do not overlap with the location of the predetermined user). Possibly, at this stage the transducer selector module  620  utilizes the mapping data obtained from the mapping module  510  to convert the location of the objects OBJ in the space to the coordinate of the relevant transducers. Then based on the location and orientation of the user&#39;s head/ear(s) in the coordinate spaces of the relevant transducers  100 , the transducer selector module  620  determine and selects the transducer(s) (e.g.  100   b ) whose location(s) and orientation(s) are best suited for providing the user with the highest quality sound field. To this end, the transducer selector  620  may select the transducer(s) (e.g.  100   b ) which have the shorter un-obstructed line of sight to the predetermined user P (to his head/ears). In case no transducer with un-obstructed line of sight is found, the transducer selector  620  may utilize the pattern recognition to process the 3D sensory data (e.g. 2D and/or 3D images from the TDSMs) to identify acoustic reflectors such near the user, and select one or more transducers that can optimally generate a sound field to be reached to the user via reflection from the objects OBJ in the space. To this end, the transducer selector  620  determines a selected transducer(s) e.g.  100   a  to be used for servicing the predetermined user to provide him with audio field, and determines an audio transmission path (e.g. preferably direct, but possibly also indirect/via-reflection) for directing the audio field to the head/ears of the user. 
     The output sound generator module  600  also includes an audio signal generator  630 , which is configured and operable to generate audio signals for operating the selected transducer to generate and transmit the desired audio field to the predetermined user. In this regards, the audio signal generator  630  encodes and/possibly amplifies the sound data from the audio input module  610  to generate audio signals (e.g. analogue signals) carrying the sound data. In this regards, the encoding of the sound data on a signals to be communicated to speakers of the selected acoustic transducer (e.g.  100   a ) may be performed in accordance with any known technique. 
     Particularly, in some embodiments of the present invention, the audio signal generator  630  is configured and operable for generating the audio field carrying the sound data only in the vicinity of the user, so that the user privately hears the audio field transmitted to him, while user&#39;s/people in his vicinity cannot hear the sound. This may be achieved for example by utilizing the sound from ultrasound technique disclosed in WO 2014/076707, which is assigned to the assignee of the present invention and incorporated herein by reference. To this end the audio signal generator  630  may include a sound from ultrasound signal generator  632  which is configured and operable for receiving and processing the sound data while implementing the private sound field generation technique disclosed in WO 2014/076707, so as to produce private sound field which can be heard only by the predetermined user to which it is directed. To this end, the relative location of the user, relative to the selected transducer (as obtained from the transducer selector  630 ), is used to generate ultrasonic beams which are directed from the transducer to the location of the user and configured to have a non-linear interaction in that region forming the localized sound field at the region of the user. 
     Additionally, the system may include a beam forming module  634  configured and operable for processing the generated audio field carrying signals to generate a plurality of beam-formed signals, which when provided to the plurality of transducer elements of the selected acoustic transducer(s) (e.g.  100   b ) generate an output acoustical beam that is focused on the user (on his head and more preferably on his ears). The beam forming module  634  of the present invention may be configured and operable for implementing any one or more of various known in the art beam forming techniques (such as phase array beam forming and/or delay and subtract beam forming), as will be readily appreciated by those versed in the art. 
     Thus the control system  500  is configured and operable to process the sensory data obtained from the TDSM(s)  110  in order to determine user(s) in the monitored space to which audio signals/data should be communicated and operate the one or more transducer units,  100   a  and  100   b , in order to provide the user(s) with hand free private audio sessions in which the user(s) privately hear the sound data designated thereto without other users in the space hearing it. 
     According to some embodiments the system includes an audio session manager  570  which is configured and operable for managing audio sessions of one or a plurality of users located in the space(s) covered by the system  1000 . The audio session manager  570  may be adapted to manage various types of sessions including for example unilateral sessions in audio/sound data is provided to the user (e.g. music playing sessions, television watching sessions, gaming and others) and/or bilateral sessions in which audio/sound data is provided to the user and also received from the user (e.g. phone/video calls/conference sessions and/or voice control/command sessions and others). To this end, the session manager may manage and keep track of a plurality of audio sessions associated with a plurality of users in the space(s) covered by the system which distinguishing between the sounds to be communicated to the different respective users and also distinguishing between the sounds received from the different respective users. 
     To this end, optionally in implementations in which the system is configured to enable users to conduct bi-directional (bi-lateral) audio communication sessions (such as telephone calls). The system  1000  includes one or more audio input sensor modules  120  distributed in the spaces/sites covered by the system. Each audio input sensor module  120  is configured and operable for receiving audio information from user(s) at the space covered thereby. The audio session manager  570  includes an input sound analyzer  560  adapted to process the audio information from the audio input sensor module  120  in order to distinguish between the sounds/voices of different users. 
     For example, the audio input sensors  120  may be configured and operable as directive audio input sensors, which can be used to discriminate between sounds arriving from different directions. Accordingly, the input sound analyzer  560  is configured and operable for discriminating the input sound from different users in the same space based on the different relative directions between the users and one or more of the directive audio input sensors  120  in that space. 
     For instance, in some cases a directive audio input sensor  120  is implemented as a microphone array. The microphone array may include a plurality of directive microphones facing different directions, or a plurality of microphones (e.g. similar ones) and an input sound beam former. Accordingly the array of differently directed directive microphones, and/or an input sound beam former (not specifically shown) connected to the array of microphones, provides data indicative of the sound received from different directions in association with the directions from which they are received. The input sound beam former may be configured and operable to process the signals received by the microphone array according to any suitable known in the art beam forming technique in order to determine the directions of different sounds received by the array. The input sound analyzer  560  may be configured and operable to associate the sounds arriving from different directions with different respective users in the monitored space(s), based on the locations of the users in these spaces, as determined for example by the user detection module  520 . More specifically, the input sound analyzer  560  may be adapted to utilize user detection module  520  in order to determine the location of different users in the space(s) monitored by the system  1000 . Then, utilizing the mapping module  510  (which in that case also holds mapping data relating the coordinates (locations, orientations, and sensing characteristics) of the microphone arrays  120  to the coordinates of the TDSMs  110 ), the input sound analyzer  560  determines to which user belongs the sounds arriving from each specific direction. Accordingly, the sound analyzer  560  associates the sound coming from each user&#39;s direction with the session of the user. Thus, whereby the output sound generator module  600  provides sounds privately to respective users of the system and the sound analyzer  560  separately/distinctively obtains the sound from each user, a bilateral audio communication can be established with each of the users. 
     As indicated above, the system  1000  may be configured as a distributed system including the one or more transducer units (typically at  100 ) and the one or more TDSMs (typically at  110 ) distributably arranged in desired spaces, such as a house, apartment, office, vehicle and/or other spaces, and a management server system  700  connected to the distributed units. For instance  FIG. 1B  shows a distributed system  1000 . The system  1000  includes TDSMs  110   a  to  110   c  and arranged in rooms R 1  to R 3  of an apartment APT and connected to the control system  500  which manages the audio communication sessions within the apartment, The system  1000  also includes the TDSM  110   e  and the transducer  100   e  arranged in a vehicle VCL, and connected to the control system  500 ′ which manages the audio communication sessions within the vehicle VCL. In various implementations of the system, the control systems  500  and  500 ′ (which are also referred to herein as local audio systems) may be connected to their respective TDSMs  110  and transducers  100  by wired or wireless connection. The management server system  700  manages the audio communication sessions of the users while tracking the locations of the users as they transit between the spaces/sites covered by the system (in this case the rooms R 1 -R 3  of the apartment APT and the vehicle VCL). 
     The server system  700  may for example reside remotely from the control systems (local audio systems)  500  and/or  500 ′ (namely remotely from the apartment APT and/or from the vehicle VCL) and may be configured and operable as a cloud based server system servicing vocal communication to the user as he moves in between the rooms of the apartment APT, from the apartment to the vehicle VCL and/or while he drives the vehicle VCL. To this end the, control system  500  or one or more modules thereof may be configured and operable as a cloud based service connectable to the plurality of TDSMs and transducers from remote, e.g. over network communication such as the internet. To this end the control systems  500  and/or  500 ′ and possibly also other modules of the system  1000 , except for the TDSMs  110  and the transducer array units  100  may be implemented as cloud based modules (hardware and/or software) and located remotely from the spaces (e.g. apartment APT, vehicle VCL and/or office) which are covered by the system and adapted to communicated with the TDSMs  110  and the transducer array units  100 . Accordingly, there may be no physical hardware related to the control systems  500  and/or  500 ′ at the spaces covered by the system. 
     To this end, the server system  700  communicates with the control systems  500  and  500 ′ to receive therefrom data indicative of the location of the user of interest (P). To this end the server system  700  receives user detection data obtained from the user detection modules  520  of the control systems  500  and  500 ′ by processing the sensing data gathered by the varies TDSMs  110  who sense the users of interest (e.g. user P) while he moves in the various spaces (rooms of the apartment and/or the vehicle). Accordingly the server system  700  tracks the user as he moves between the various spaces, while managing the audio session(s) of the user as he moves. In case the user, while in active audio session, moves from the coverage spaces of the TDSMs and transducers of one/first control system (e.g.  500 ) to the coverage zone of another/second control system (e.g.  500 ′), the server system  700  operates the second control system  500 ′ to continue the active audio session of the user. 
     Indeed, in some cases the user may move to places/location at which no TDSMs  110  and no transducers  100  are installed. For example when the user walks on the path between the apartment APT and the vehicle VCL. Therefore in some embodiments that the server system  700  further includes a mobile session module  710  (e.g. a modem) in which is capable of transferring the audio communication session to a mobile device MOB of the user (e.g. a preregistered mobile device such as a mobile phone prerecorded in the server  700  as associated with the user) in order to allow the user to maintain continuous audio session while he transit between different spaces. Thus, once the user exit the coverage zones of the system he can continue with his audio session via his phone. 
     Alternatively or additionally, in some implementations, the system  1000  includes one or more full package units which include at least one transducer unit  100 , at least one TDSM  110 , and optionally an input audio sensor (microphone array)  120  packaged together in the same module. This is illustrated for example in  FIG. 1C , and in  FIG. 1B  see modules  100   a + 110   a  and  100   c + 110   c . Optionally the full package units also include the control unit  500  and the audio session manager  570 . 
     In this case the transducer unit  100  and the TDSM  110  are preinstalled within the package and the relation between the coordinates of their sensing volumes and coverage zones are predetermined apriority and coded in the control unit&#39;s mapping module  510  (e.g. memory). Accordingly no calibration of the mapping between the TDSM and the transducer is required in this case. To this end full package unit of this example is configured to be deployed in a certain space, without calibration and may be used to provide private audio communication session to the user at the space at which it is deployed. 
     Generally however, calibration may be required in order to determine the mapping data associating the coordinate spaces/systems of the transducers (e.g. C′) the coordinates spaces/systems of the TDSMs (e.g. C), and possibly also the coordinate system of the audio input sensors  120 . More specifically calibration may be required in cases where the transducers and the TDSMs are located separately as illustrated in  FIG. 1B , To this end, optionally the mapping module  510  includes a calibration module  514  configured and operable for obtaining and/or determining calibration data indicative of the relative locations and orientations of the different TDSMs and transducers and possibly also of the audio input sensors  120  that are connected to the control system  500 . 
     In some embodiments the calibration module  514  is adapted to receive manual input calibration data from a user installing the system  1000 . For instance such input data may be indicative of the relative locations and orientations of the TDSMs and the transducers, and the calibration module  514  may be adapted to utilize this data to determine mapping data indicative of coordinate transformations between the coordinates of the TDSMs  110  and those of the transducers  100  and possibly audio input sensors  120 . 
     Alternatively or additionally, the calibration module  514  may be adapted to implement and automatic calibration scheme in which the sensing capabilities of the TDSMs  110  and possibly also the audio sensing capabilities of the audio input sensors  120  are employed in order to determine locations and orientations of the TDSMs  110  relative to the various transducers  100  and/or input sensors  120 . To this end, in some embodiments the calibration module  514  utilizes the pattern recognition engine  515  in order to process the data sensed by each TDSMs  110  to identify the transducers  100  and possibly audio input sensors  120  located in the sensing zone of each TDSM and determine their relative locations and orientations relative to the TDSMs  110 . 
     Indeed, in some embodiments in order to identify the transducers  100  and optionally identify the audio input sensors  120 , the calibration module  514  utilizes certain pre-stored reference data indicative of the appearance and/or shape of the transducers and/or the audio input sensors. This reference data may be used by the pattern recognition engine  515  to identify these elements in the spaces (sensing volumes SVa-SVn) monitored by the TDSMs. 
     Moreover, optionally, according to some embodiments the transducers  100  and possibly the audio input sensors  120  are configured with a package carrying identifying markers (e.g. typically visual passive markers, but possibly also active markers such as active radiation emitting markers) and/or acoustic markers and/or other markers which aid at identifying the types and the locations and orientations of the transducers  100  and/or the audio input sensors  120  by the TDSMs. To this end, the markers should be of a type identifiable by the sensors included in the TDSMs. In such embodiments the pre-stored reference data used by the calibration module  514  may include data indicative of the markers carried by different types of the transducers  100  and/or the audio input sensors  120  along with the respective types and audio properties thereof. The reference data may be used by the pattern recognition engine  515  to identify the markers in the spaces (sensing volumes SVa-SVn) monitored by the TDSMs, and thereby determine the relative locations and orientations of the transducers  100  and optionally the audio input sensors  120 . 
     Yet alternatively or additionally, the calibration module may be adapted to carry out an active calibration phase in which the location of the transducers is determined by sensing and processing sound field generated by the transducers during the calibration stage and locating (e.g. echo-locating) the transducers based by detecting and processing the calibration sound fields generated thereby (e.g. by employing the TDSMs  110  and/or the audio input sensors  120  to sense these sound field and process the sensed sound fields; e.g. utilizing beam forming) in order to determine the relative location and orientation of the transducers relative to the TDSMs and/or  110  and/or the audio input sensors  120 . 
     Thereafter, once the relative locations and orientations of the transducers  100  are determined, the calibration module  514  determines the coordinate transformations between the coordinate spaces/systems of the transducers  100  (the coverage zones&#39; CZa-CZm coordinates of the transducers  100   a - 100   m  by which the system can adjust/control the direction and/or location of the generated sound field), and the coordinate spaces of the sensing zones SVa-SVn of the TDSMs. This allows to generate the mapping data of the mapping module which enables to accurately select and operate the selected traducer in order to generate and direct a sound field towards a location of a user P detected by one of the TDSMs. Optionally, in the same way, the calibration module  514  determines the coordinate transformations between the coordinate spaces/systems of the coverage zones (not specifically shown in the figures) of the audio input sensors  120 , by which the system receives the sounds from the users, and the coordinate spaces of the sensing zones SVa-SVn of the TDSMs. This allows to generate the mapping data enabling to accurately determine the user whose voice is received by the audio input sensor(s)  120 . 
     It should therefore be noted, although not specifically shown in the figure, that the control system  500  and generally the system  1000  include one or more communication input and output ports for use in network communication and/or for connection of additional one or more elements as the case may be. 
     In some embodiment, system  1000  may also include one or more display units  130  connectable to the control unit  500  and configured and operable for providing display data to one or more users. The control unit  500  may receive data about location of a user from the user detection module and based on this location data, determine a suitable display unit  130  for displaying one or more selected data pieces to the user, and to further select an additional display unit  130  when the user is moving. The control unit may operate to display various data types including but not limited to one or more of the following: display data associated with another user taking part in an ongoing communication session, display data selected by the user (e.g. TV shows, video clips etc.), display commercial data selected based on user attributes determined by the system (e.g. age, sex), etc. The control unit  500  may allow the user to control the displayed data using one or more command gestures as described further below. Additionally, in some embodiments the display is also a part of a user interface of the system (possibly also including user input device  130  such as keyboard and/or touch-screen and/or gesture detection), that is configured and operable as a system setup interface presenting the user with setup and configuration parameters of the system and receiving from the user instructions for configuring the setup and configuration parameters of the system  1000 . 
     The one or more TDSMs  110  are configured for providing data about three dimensional arrangement of a region within one or more corresponding sensing zones. To this end the one or more TDSMs  110  may include one or more camera units, three dimensional camera units, as well as additional sensing elements such as radar unit, LiDAR (e.g. light based radar) unit and/or sonar unit. Additionally the control unit  500  may be configured to operate the one or more transducer units  100  to act as one or more sonar units by scanning a corresponding coverage volume with an ultra-sonic beam and determined arrangement of the coverage volume in accordance with detected reflection of the ultra-sonic beam. 
     As indicated above, the transducer units  100  may each include an array of transducer elements.  FIG. 3  shows an example of such transducer unit  100  which may be included in the system  1000  and which is particularly suited for implementing a sound from ultrasound technique (such as that disclosed in WO 2014/076707) for generating a localized sound field (e.g. a confined sound bubble) within its coverage zone (e.g. in the vicinity of the head/ear(s) of a designated user of interest). The transducer unit  100  includes: an array of transducer elements  105  configured to emit acoustic signals at ultra-sonic (US) frequency range, and a sound generating controller  108  configured to receive input data indicative of an acoustic signal to be transmitted and a spatial location to which the signal is to be transmitted. The sound generating controller  108  is further configured and operable to operate the different transducer elements  105  to vibrate and emit acoustic signals with selected frequencies and phase relations between them. Such that the emitted US signals propagate towards the indicated spatial location and interact between them at the desire location to generate audible sound corresponding to the signal to be transmitted as described further below. In this connection the terms transducer array, transducer unit and transducer array unit as used herein below should be understood as refereeing to a unit including an array of transducers elements of any type capable of transmitting acoustic signals in predetermined ultra-sound frequency range (e.g. 40-60 KHz). The transducer array unit may generally be capable of providing beam forming and beam steering options to direct and focus the emitted acoustic signals to thereby enable creation of bright zone of audible sound. 
     The one or more microphone arrays  120  are configured to collect acoustic signals in audible frequency range from the space to allow the use of vocal gestures and bilateral communication session. The microphone array  120  is configured for receiving input audible signals while enabling at least certain differentiation of origin of the sound signals. To this end the microphone array  120  may include one or more direction microphone units aligned to one or more different directions within the space, or one or more microphone units arranged at a predetermined distance between them within the space. In this connection it should be noted that as audible sound has typical wavelength of between few millimeters and few meters, the use of a plurality of microphone units in the form of phased array audio input device may require large separation between microphone units and may be relatively difficult. However, utilizing several microphone units having distances of few centimeters between them and analyzing audio input according to time of detection may provide certain indication about direction and location of the signal origin. Typically it should be noted that audio input data may be processed in parallel with sensing data received by the one or more TDSMs  110  to provide indication as for the origin of audio input signals and reduce background noises. 
     The control/processing system  500  is configured and operable to provide hand free private sound communication to one or more users located within the space where the system is employed. Generally, the system  1000  is configured and operable to initiate, or response to initiation from a user, an audio communication session of one or more users while providing private sound region where only the selected user can hear the sound signals. To this end, the control unit  500  utilizes the sensing data about three dimensional arrangement of the space to determine location of a selected user, the transmits acoustic signals of two or more selected ultra-sonic frequencies with suitable amplitude, phase, frequencies and spatial beam forming to cause the ultra-sonic signals to interact between them at vicinity of the selected user to demodulate frequencies of audible sound. This provides a region of sound that the user can hear, while the sound cannot be heard outside of a relatively small region. To this end the control unit  500  is generally configured to provide certain data processing abilities as well as calibration data indicative of correspondence between coverage zones of the transducer array units  100  and sensing volumes of the TDSM units  110 . As indicated above, such calibration data may be pre-stored or automatically generated by the system. The control system  500  and/or the audio session manager  570  may include an audio input module  610  configured and operable for communicating with one or more audio sources (e.g. local or remote communication modules and/or other audio data providers) to obtain therefrom audible data to be provided to the user. Also, the control system  500  and/or the audio session manager  570  may include an audio analyzer  560  configured and operable for receiving input audio signals from one or more microphone units  120 . The control system  500  may also include a gesture detection module  550  configured and operable to process the audio signal from the microphone units  120  to determine if an audio signal indicative of one or more gestures was received from a user of the system, and possibly associate such gestures with certain instructions received from the user (e.g. user&#39;s instructions with respect to an ongoing communication session of the user and/or initiation of a communication session etc′). 
     The mapping module  510  is connectable to the one or more TDSM  110  units and configured and operable to receive input indicative of three-dimensional sensing data of the respective sensing volumes. The mapping module  510  is further configured for processing the input sensing data and generate a three dimensional (3D) model of the one or more respective sensing volumes of the TDSMs. In cases where the system is configured as a distributed system, e.g. as in the present example of  FIG. 1B , the mapping module of one control unit  500  may be configured to communication along a suitable communication network with mapping modules of one or more other audio communication systems connected thereto. Additionally or alternatively, the mapping module may be pre-provided with data about arrangement of the different transducer units  100 , TDSM units  110  and microphone units  120  to thereby enable correlations between sensing data and recipient location determined by the TDSM units  110  and corresponding transducer units  100 . 
     The user detection module  520  is configured and operable for receiving input sensing data from the one or more TDSMs  110  and for processing the input sensing data to determine existence and location of one or more people within the corresponding sensing volume. In this connection, the user detection module may include or be associated with a pattern recognition engine/utility  515  which is configured and operable for recognizing various objects in the image(s) obtained from the TDSMs  110 . For that matter it should be understood that the images of the TDSMs  110  may include: visual images(s) and/or IR image(s) and/or echo-location image(s) and/or depth image(s) and/or composite image(s) comprising/constructed from any combination of the above. The exact types of image information obtained from the TDSMs  110  may generally depend on the specific configuration of the TDSMs used and the sensors included therein. To this end, the term image should be understood here in its broad meaning relating to a collection of data pixels indicative of the spatial distribution of various properties of the monitored space, such as various spectral colors, depth and/or other properties. The pattern recognition engine/utility  515  may utilize various types of image processing techniques and/or various pattern recognition schemes as generally known in the art, for identifying people and/or their heads/ears (e.g. P in  FIG. 1B ) and possibly also other recognizable objects (e.g. OBJ in  FIG. 1B ) in the space/sensing volume(s) monitored by the TDSM(s) and determining their location in the monitored space. This allows for separating image data portions associated with people or generally foreground objects from the background image data. 
     To this end in some implementations pattern recognition engine/utility  515  is configured and operable to apply pattern recognition processing to the image(s) obtained from the TDSMs  110  and to thereby generate a 3D model of the spaces monitored by the TDSMs. In turn the user detection module  520  may be adapted to determining (monitoring) and tracking (in time) the location(s) (e.g. 3D location) of one or more user(s) (e.g. of the user of interest P) based on the 3D model of the space generated by the pattern recognition engine/utility  515 . Accordingly the user detection module  520  determine desired location at which to generate private sound region (sound bubble) for the user(s) of interest P, such that said location is centered on a selected user&#39;s head, and more preferably centered on/near the individual ear(s) of the user 
     In some configuration of the system, the user detection module  520  may include, or be connected to, one or more of face recognition module  530  (which is also referred to herein interchangeably as face/user recognizes), orientation/head detection module  540 , and gesture detection module  550 . Generally, it should be noted that the user detection module  520  is configured and operable for processing input sensing data utilizing one or more generally known processing algorithms to determine existence of one or more people (potential users) within the corresponding sensing volume. The face recognition module  530  may generally be configured to receive sensing data (e.g. the images of the TDSMs) indicative of existence and location of one or more selected users and to process the data by one or more face recognition techniques to determine identity of the one or more detected users. The face recognition module  530  is thus configured and operable for generating identity data indicative of the locations and identities of one or more detected user(s) and for providing the identity data to the output sound generator module  600  to enable the transducer selector  620  to select a suitable transducer unit and operate it for generating local private sound region audible to a selected user. The face recognition module  530  may be adapted to provide the identity data also to the received sound analyzer  560  so that the latter can process the sounds received from the audio input sound to determine/recognize/separate the sounds arriving from each particular user in the monitored space. In some embodiments, the face recognition module  530  may also be adapted to perform casual pairing and determine the user age/sex for purposes such as delivering commercials etc. 
     The output sound generator module  600 , and the audio input module  610  may generally provide data about input audio signal to the user detection module  520  in accordance with location of a user, one or more gestures provided by the user (e.g. vocal gestures) and bilateral ongoing communication session. 
     To this end, the orientation/head detection module  540  is configured to receive at least a part of the sensory data from the TDSMs and/or at least a part of the 3D model obtained from the pattern recognition module  515 , which is associated with the location of user of interest P, and to process the sensory data to determine location of the selected user&#39;s head and possibly also the orientation of the user&#39;s head. Accordingly the orientation/head detection module  540  may provide the data indicative of the location and orientation of the user&#39;s head to the output sound generator module  600  so that the latter can generate a local/confined sound field in the vicinity of (e.g. at least partially surrounding) the user&#39;s head. 
     As discussed in more details below, in some embodiments of the present invention the head orientation module  540  is further configured processing the sensing data from the TDSMs and/or the 3D model obtained from the pattern recognition module  515  in order to determine data indicative of the location and orientation of the user&#39;s ear(s) and provide such data to the output sound generator module  600  so that the latter can generate a local/confined audible sound field at least partially surrounding the user&#39;s ear(s). 
     As indicated above, the head orientation module  540  and/or the transducer selector module  620  may also generate data indicative of line of sight between one or more transducer units and the user&#39;s ears/head. In this connection it should be noted that in some embodiments the one or more transducer units  100  and the one or more TDSMs  110  may be configured within a single physical package to simplify deployment of the system. 
     As shown for example in  FIG. 1C , in some embodiments, providing distributed processing, such physical package may also include the control system  500  and additional elements (not specifically shown) such as memory and communication utilities and power supply unit that are not specifically shown here. In some other configuration, the physical unit (namely with the same package) may include the transducer unit  100 , TDSM  110 , microphone unit  120 , power supply unit (not specifically shown), and a communication utility (not specifically shown) providing communication with a remote control system  500 , which is configured to receive and process the sensory data selectively transmit the physical distributed unit data about audio communication sessions. 
     Thus, a line of sight determined by the orientation detection module  540  based on sensory data may typically be indicative to line of sight of a corresponding transducer unit  100 . In some configurations of the invention, the orientation detection module may be configured to select a transducer unit  100  most suitable for transmitting selected acoustic signals to a recipient in accordance with determined location of the recipient&#39;s head/ears. 
     Reference is now made more specifically to  FIG. 1D  in which the audio communication system  1000 , similar to that of  FIG. 1A , is presented in user-centric manner illustrating in more details the communication services facilitated by the system  1000  to the user U. Indeed as described above, it should be understood that, the system  1000  may provide services, simultaneously or intermittently/successively, to several users, which may possibly reside at different sites/locations (depending on the distribution of the system at said sites). Without loss of generality,  FIG. 1D  illustrates how the system  1000  is configured and operable for providing the communication services to a certain user U. As illustrated in  FIG. 1D , from a user-centric perspective the similar modules with similar/like functionalities as illustrated and described above with reference to  FIG. 1A  are arranged in the following layers: 
     I. A User Interface (UI) Layer 
     The user interface (UI) layer is a so-called physical layer responsible of receiving physical/signal/sensory inputs and producing physical/signal/sensory outputs from and to the user. As illustrated the user interface (UI) layer generally include the input modules for receiving/sensing information about the user, and output modules for providing interacting with the user; 
     The input modules of the user interface include the following:
         (i) the above-described sensors/TDSMs  110  which are, designated to be located in one or more sites and configured and operable to provide sensory data (e.g. optical/sonar/depth data) about respective sensing volumes within the sites. The sensory data may be indicative of the position orientation, posture and movements of the user U within the sensing volumes (processing the sensory data to derive the above properties of the user may be accomplished for example by the recognition layer described in the following);   (ii) the above-described microphones and/or microphone arrays  122  (with or without the audio beamformers  124 ) arranged in the one or more sites. The microphones are adapted to sense sound/vocals produced by the user U, whereby distinction between the sounds from the user and other sounds may be achieved for example by beamforming of the received sounds to discriminates sounds arriving from the user&#39;s position, and/or by processing/vocal-pattern-recognition of the user&#39;s voice.   (iii) Optionally, the user interface layer also includes additional input modules  130 .I of the above-described UI  130 , such as key-board, computer mouse, gam controllers, or touch screen/pad (for example of a mobile device or a computerized system of the user), which may be connected to the system  1000  and with which the user can interact in the conventional ways to provide inputs to the system  1000 .       

     The output modules of the user interface layer may include the following:
         (i) The above described one or more transducers  100  to be located in one or more sites and capable of forming audible sound fields within respective coverage zones thereof; The transducers  100  may be conventional audio transducers capable of generating audible sound wide spread over their respective coverage zones, and/or may include transducer arrays for production of localized audible sound from ultrasound in the vicinity of the user&#39;s head/ear(s), such that the sounds can be privately heard by the user U and substantially not heard by other persons in his vicinity.   (ii) Optionally the output modules of the user interface layer may also include a display, or a display interface,  130 . 2  for presenting the user with visual information (e.g. display interface for connecting to a predetermined display—e.g. of a user&#39;s device).   (iii) Optionally the output modules of the user interface layer may also include a haptic feedback unit/module, or an interface to such haptic feedback unit/module,  130 . 3  by which haptic feedback can be provided to the user (e.g. the haptic feedback interface may be an interface adapted for connecting/communicating with a predetermined haptic feedback unit/module of the user—e.g. exploiting haptic capabilities of preexisting user&#39;s personal device). In some embodiments, the transducers  100  may be utilized to provide both private audio and far-field haptic sensations, using focused ultrasound.       

     Thus, with the above-described user interface layer, the system  1000  as described in  FIGS. 1A and 1D  above, may received acoustic-optical information about the user&#39;s U behavior (including the user&#39;s location, posture, movement, and vocal signature), and may output in response, at least an audible sound with sound data to be privately or publicly heard by the user. 
     From a user-centric perspective some of the modules illustrated and described with reference to  FIG. 1A  above, facilitates such interaction with the user U and are arranged in Recognition and Artificial-Intelligence (AI) layers as described in the following: 
     II. The Recognition Layer 
     The recognition layer primarily includes the above-described user detector  520  (user detection module) which is connectable to the one or more TDSMs/spatial-sensors  110  described above for receiving therefrom the spatial sensory data about the sensing volumes (monitored sites/spaces) at which the user may reside U, and also connectable to the audio input sensors  120  (e.g. microphones  122  and/or audio beamformers  124 ) for receiving therefrom the auditory/sound sensory data from the sensing volumes. The user detector  520  is configured and operable to apply recognition processing to sensory data to identify the at least one user U within the sensing volumes. As indicated above the user detector  520  includes:
         i) the user/face recognizer  530 , which is capable of processing the spatial sensory data received from the monitored sites/spaces to identify the user U within monitored sites;   ii) the received sound analyzer  560  which is capable of processing the input audio signals received from said sites to determine data indicative of received sound originating from the user U;       

     As will be appreciated from the below description, the user/face recognizer  530  as well as the received sound analyzer  560  may be adapted to perform complex pattern recognition processing in the spatial/visual optical region as well as the acoustical/auditory sound regime to identify and recognize the user U, his posture and movements, as well as recognition of auditory sounds (vocals/verbals) originating from him or auditory sounds to which the user is exposed. For that end to be achieved, the user/face recognizer  530  as well as the received sound analyzer  560  may be facilitated with pattern recognition engine/processor  515  trained or trainable with reference pattern data (spatial/imagery pattern data and/or auditory/sound pattern data) facilitating accurate pattern recognitions. 
     Moreover, as also described below, in some embodiments the user/face recognizer  530  is also equipped with anthropometric model(s) characterizing the special appearance and relations between various features of the user or his face. The anthropometric model(s) may include a general model suited for various users, or a customized model(s) of the specific user U. In some implantations the system  1000  is trainable system, as generally known in pattern recognition training techniques. In such embodiments the system is initially equipped and starts with a general anthropometric user model and is trained during operation to recognize the specific characteristics of different users U of the system  1000  and during such training constructs a specific more accurate anthropometric models for specific users of the system. Given the general or the user-specific, anthropometric model, the user/face recognizer  530  processes the spatial sensory data from the sensors  110 , to identify the user U therein (e.g. identify portions of the sensory data which may be representative of the user), and utilize the pattern recognition to identify the user and optionally determine his facial expression or posture, for instance by matching the sensed data with the anthropometric facial or bodily model of the user. Thus, preferably in some implementations the user/face recognizer  530  yields data indicative of the identified user U, as well as data indicative of the user&#39;s posture and/or facial expression. 
     Furthermore, the received sound analyzer  560  may be adapted to discriminate the user&#39;s U voice from other received sounds. To achieve that the received sound analyzer  560  may for example utilize the position of the user as determined by the user/face recognizer  530 , and operate the beamformers  124  to filter out received sound from locations other than that location to identify the user&#39;s originated voice or other sounds, or vice versa, in order to determine sounds other than the user&#39;s sounds to which the user is exposed. Alternatively, or additionally, discrimination of the user&#39;s U voice may be based on the specific spectral signature of the user&#39;s voice. For that, optionally, the received sound analyzer  560  may include reference data  562  about the user&#39;s U voice and may utilize this reference data to extract and discriminate the user&#39;s U voice from the received sounds by filtering out the parts (e.g. spectral parts) of the received sounds that do not fit the model  562  of the user&#39;s voice, or vice versa in order to determine sounds other than the user&#39;s voice to which he is exposed. It should be understood that the model  562  of the user&#39;s U voice may be evolvable/trainable model and the system  1000  may be adapted to learn the user&#39;s U voice and train and adjust this model  562  accordingly during successive interactions with the users, so that the user&#39;s voice can be more easily recognized and possibly also the user state (e.g. sleeping/wakening/awake, preoccupied/engaged/relaxed etc′) may be identified based on the variations in the spectral signature of the user&#39;s voice. Yet additionally, as also described below, in some embodiments the received sound analyzer  560  may be adapted to process the received sounds, or at least the identified parts thereof that are associated with the user&#39;s U own voice, by utilizing a natural language processor (NLP)  561  to interpret the language and decipher, e.g. by speech recognition, the meaning/intent of the vocal expressions by the user (similarly NLP  561  may be used to decipher the meaning of other voices to in the surroundings to which the user is exposed). It should be noted that for determining/estimating the user state, the system may implement the above-described pattern/speech recognitions of the sensors/microphones, either locally and/or using remote compute resources (e.g. cloud-based). Accordingly, the modules  530  and  560  may be implemented as local or cloud-based modules. 
     III. The AI Layer 
     As indicated above, in some embodiments the system  1000  provide hand free communication, as well as to provide hand free management and control of the system. For that end to be achieved, on top of the indicated above which are capable of detecting various aspects of the state of the user U, the system  1000  utilizes an artificial intelligence (AI) layer capable of processing the various recognized aspects of the state of the user U, and determining actions to be carried out by the system  1000  in response to the recognized user&#39;s state. The various aspects of the user state that may be processed by the AI layer including for instance the data/patterns recognized by the pattern recognition modules  530  and  560  of the recognition layer, which pertain to the user&#39;s speech, location, pose, movement, as well as audible sounds to which the user is exposed. 
     In an example the AI layer includes a gesture detector  550  (gesture detection module), which may be adapted to process the above indicated various aspects of the state of the user U to determine command or more generally messages expressed by the user, via such gestures. The gesture detector  550  is generally configured and operable to process directly or indirectly, the spatial input sensing data (from sensors  110 ), which is associated with one or more selected users U, and to process and analyze the input data to detect user behavior/movement associated with one or more predetermined gestures defined to initiate one or more commands/actions in response to the user. In some embodiments, the gesture detection module  550  may also be configured for receiving and processing, directly or indirectly, the audio signals, which are received from the user(s) and collected by the microphone array  120 , to detect one or more vocal gestures associates with one or more predetermined commands. In this connection it should be noted that the term gesture herein should be construed as relating to forms of both verbal/vocal communication and non-verbal or non-vocal communication expressed by visible bodily actions (such as movement of hands, face, or other body parts), and which communicate particular messages such as the user&#39;s feelings/sentiments and thoughts, either in place of, or in conjunction with, speech or other vocal gestures). Non vocal/verbal gesturers may be detected by the spatial sensors  110  (TDSMs) of the system. Vocal/verbal gestures may be detected by the audio input sensors  120 . 
     More specifically, according to an embodiment of the present invention, the gesture detector configured and operable to carry out gesture recognition processing according to at least one of the following to thereby identify one or more vocal or non-vocal gestures of said user:
         c. apply the processing to at least a part of the sensory data associated with a spatial location of the at least one user, to identify a non-vocal gesture made by said user;   d. apply the gesture recognition processing to at least the sound originating from the user, to identify a vocal gesture made by said user;       

     Generally, to provide hand free audio communication, as well as to provide hand free management and control of the system  1000 , the audio session manager  570 , may be configured and operable to be responsive to one or more predetermined gestures (movement and/or vocal) of the user identified by the gesture detector  550  and to initiate one or more predetermined operation commands in response to the detected gestures. 
     Further in some embodiments, some of the operation commands may include one or more commands associated with external elements configured to receive suitable indication from the audio communication system of the invention. Such operation commands may for example include:
         command for initiating in an audio communication session (e.g. telephone conversation with selected contact person),   a request for notification based on one or more conditions, and any other predetermined command defined by the system and or user.       

     The session manager  570  may include action decision module  572  which is determining a desired action to be conducted by the system based on a gesture identified by the gesture detector  550 . In a simple implementation action decision module  572  may include gesture-command association (e.g. algorithm or reference data such as lookup table) capable of associating gestures (e.g. predetermined gestures) with commands/actions (e.g. predetermined commands/actions) to be executed by the system in response to the detected gestures. In more advanced implementations, the session manager  570  implements or is incorporated with an action decision AI engine  572  that is capable of processing the received gestures and determined the commands expressed thereby and the required actions from the system  100  in response. 
     In this connection it should be noted that in some implementations the one or more gestures that are identified by the system may include for example one or more of the following:
         a. One or more gestures indicating the user request for the system to transfer from public to private communication mode and vice versa;   b. One or more gestures presenting a user request for specific content to be presented to him in audio, visual or haptic forms;   c. One or more gestures indicating a user&#39;s request for having a notification or alarm set upon fulfilment of one or more conditions (e.g. house intrusion; predetermined schedule or cooking etc′).   d. One or more gestures presenting a user request for autonomous presentation of one or more types of entertainment content by the system.       

     The above also clarifies the required feedback/gesture-responsive actions to be performed by the system in response to said gestures, namely actions relating to: switching the system interaction with the user from public to private communication mod; and vice versa; provision of specifically request or autonomously selected content, to the user utilizing auditory, visual or haptic forms; scheduled notifications/alarms and or other actions. 
     As indicated above these gestures and their meaning may be apriori set/fixed (e.g. in dereference data of the system), or the system may employ AI according to any known in the art technique in order to learn what the user means/requests by particular vocal/verbal or non-vocal gesture. It should be also noted that the employment of AI may be local or cloud based, and may be on global AI training for many users, or a user specific AI training, or as based on a combination of global AI training for providing the basis of the AI and user specific training applied to the globally trained AI per each user of interest, so that the AI gets “familiar” with the specific users of interest, and can respond to them more accurately (e.g. the user state information, as determined by pattern/speech recognition of the sensors/microphones can be utilized in a heuristic, machine learning, cloud-based AI or other software system to identify appropriate to provide to the user in response to various gestures thereof). 
     In addition to the feedback/gesture-responsive actions which may be performed by the system  1000 , in response to gestures made by the user, in some implementations the system is also configured and operable for autonomously determining some actions that need to be conducted, based on the user-state of the user. 
     As indicated above and further discussed below, in some embodiments the system  100 , particularly the session manager  570 , may include a response detection module  571  that is configured and operable to determine contextual data relating to the user&#39;s environment/behavior and state. More specifically, the user response detector  571  is adapted to process the data received from the pattern recognition modules  530  and  560  as indicated above, to determine/estimate and monitor a user-state of the identified user U. For instance, such contextual data may be indicative of the user&#39;s reaction/response so some occurring even affecting the user such as a signal/or an audio content that is communicated to the user. As indicated above the received sound analyzer  560  may be capable of discriminating the sounds to which the user is exposed, and the gesture detector  550  is capable of recognizing the user&#39;s gestures (vocal/verbal no-vocal gestures), which if occur in time proximity, may be gestures provided in response to the sounds to which the user was exposed. In turn, the is configured and operable to receive data indicative of inputs from the sensors  110  and  120 , particularly for example receive that data indicative of sounds/contents to which the user is exposed (e.g. from the pattern recognition modules  530  and  560 ), and to utilize the gestures detected by the gesture detector  550  to analyze/process/estimate the user&#39;s response/reaction to these sounds/contents. Accordingly, the response detection module  571  may process the same to identify cause and effect relations between the user response/reaction to various inputs, or vice-versa identifying the contextual reason for the user response/reaction. The cause-and-effect relations are indicative of a user&#39;s sentiment/desired-response to various events to which he is exposed. 
     In some implementations the action decision AI engine  572  not only processes the gestures identified by the gesture detector  550 , but also received data from the response detection module  571  indicative of the context of the user&#39;s gesture/reaction, e.g. whether the user&#39;s gesture is provided in response to some signal content/event to which the user was exposed. Accordingly, in determining the required actions to be implemented by the system, not only the user&#39;s gesture may be taken into account but also the context at with this gesture is made. This may provide for more natural AI interaction with the system. For instance, the system  1000 , or more specifically artificial intelligence engine of the action decision AI  572  of the session manager  570  processes and learns the user state as provided by the response detection module  571  (e.g. as recognized by the pattern recognition modules  530  and/or  560 ) and possibly also processes the timely related user gestures detected by the gesture detector  550  in relation to the times of various user states, and based on an adaptive AI learning process, autonomously predict/estimates a suitable autonomous action to be implemented by the system  1000  in order to improve the user&#39;s state. 
     It should be noted that the “cause” of the cause-and-effect relations are generally also associated with the specific state of the identified user U, which may be construed to include the following properties:
         intrinsic user state indicative of the user&#39;s activity (sleeping, awake, working, dancing, cooking, playing, training, etc′); and   extrinsic user state indicative of the contextual location and environment at which said user&#39;s activity takes place (alone or with other persons/public, being engaged in local or remote social communication, environmental conditions to which the user is exposed, as well as audible sounds to which the user is exposed, the location of the user etc′).
 
The “effect” of this cause-and-effect relations would be the desired user response to the situation presented by the user state (by the “cause”). The goal of the adaptive AI learning process of the action decision AI  572 , would be to autonomously predict/estimates a suitable autonomous action to be implemented by the system  1000  in order to improve the user&#39;s state, and obviate/reduce a need for the user to take any further action in relation with the “cause”. As will be readily appreciated by those versed in the art, identification of the cause-and-effect relations may require a learning process based on accumulated monitoring of user reactions over time. Accordingly, in some implementations the response detection module  571  an artificial intelligence module/engine according to any suitable technique known in the art that would be able to accurately estimate the user-state based on data provided to the response detection module  571  from the sensors or from the pattern recognition modules. In turn, the action decider  572 , may be trainable to monitor both the user state (as obtained from  571 ) and the related user gestures (as obtained from  550 ) to be able to autonomously predict/estimates and implement actions that may be carried out by the system in order to improve the user state (in case improvement is assessed to be required), such that to obviate/reduce a need for further user action in relation to such state.
       

     It should be noted that the AI engines employed by either response detector  571  or the action decider  572  may be configured and operable according to any suitable AI technique as will be appreciated by those versed in the art, and may be implemented locally and/or via cloud-based modules/services. These AI trainings may be based on global AI training which are conducted based on the responses and reactions of many users, or it may be a user specific AI training. In some implementations the initial training is global AI training and user specific training may be further applied to the globally trained AI, per each user of interest, so that the AI gets “familiar” with the specific users of interest, and can respond to them more accurately. Accordingly, in some embodiments the audio session manager  570  of the system is also configured and operable for autonomously determine one or more actions, being autonomous actions, to be performed by the audio communication system  1000  in response to at least one of the intrinsic and extrinsic properties of the monitored user-state. 
     Thus, according to embodiments of the invention the system  1000  is configured and operable for deciding about gesture-responsive actions (feedback actions) to be implemented by the system in response to verbal/vocal or non-vocal gestures of the user U of the system. As indicated above the gesture-responsive actions which may be conducted by the system may for instance include one or more of the following:
         a. switching the system interaction with the user from public to private communication mode, and vice versa;   b. provision of specifically requested content, to the user utilizing one or more of auditory, visual and haptic forms;   c. provision of autonomously selected content (e.g. based on general request of the user) utilizing auditory, visual or haptic forms;   d. Activation of private or public notification or alert according to user-initiated schedule.
 
Alternatively or additionally, according to embodiments of the invention the system  1000  is configured and operable for deciding about autonomous actions to be implemented by the system in response to certain user-states. The autonomous actions which may be conducted by the system may for instance include one or more of the following:
   e. Activation of private or public notification or alert in response to certain identified user state;   f. Activation of private or public user authentication (e.g. in case the user is not authenticated by the system);       

     It should be noted that some of the above listed actions might require retrieval of content (e.g. sound data or visual data or haptic content) to be presented/provided to the user U. The content may be for example retrieved by action decider  572  or by an AI module therefor, from either a local content repository or from on-line content providers such as Search Engines, websites, social networks or others. Local and or remote AI may generally be used as known in the art to assess the best suitable content to be provided in response to the user request, based on the user&#39;s preferences (e.g. as those are often listed by content providers). 
     The above listed actions a. to f, as well as other possible actions, might be implemented by the system in various forms and/or utilizing various means. As shown in  FIG. 1D , the following one or more user interface output means (i) to (vi) may be included or connectable to the system  1000  and may be used by the system to perform the required actions: 
     Private UI output means may include:
         A. private transmission of ultrasound signals by said one or more transducers  100  to form local audible sound field with said sound data is formed in close vicinity of said user;   B. provision of haptic feedback to said user via a personal user device (mobile-phone, smart-watch, etc′) connectable to the system and having a haptic feedback functionality/interface  130 . 3 ;   C. provision of display content to said user via display device (or interface thereof)  130 . 2  which is connectable to the system and characterized as a private display (e.g. virtual or augmented eyewear display, or a display of personal user device which is defined as private);       

     Public UI output means may include:
         D. public transmission audible sound signals by said one or more transducers to form with said sound data at a region of said user;   E. provision of display content via a display device (e.g. a TV) connectable to the system;   F. initiation of alarm via an alarm system connectable to the system;       

     In the above list the UI output means are divided to:
         A. private output means ((i)-(iii)), whose content can be provided privately to the user without invoking awareness of other individuals to the provided content or to its provision and reception by the user. And   B. public output means ((iv)-(vi)) whose content is generally provided publicly in such a manner that the content and/or its provision may be exposed to, or invoke awareness of, other individuals.       

     Thus, in some implementations, one prominent property about of any action to be performed by the system in response to either the user&#39;s state or a gesture performed by the user, is related to how to perform the required action in terms of privacy. More specifically, as indicated above, in various implementations of the system  1000  of the present invention, the one or more of the transducers of the system are operable for emitting ultra-sonic signals and directing and/or focusing the ultra-sonic signals at a spatial position within their respective coverage zone. In turn, the output sound generator is capable of selecting and operating the at least one selected transducer for generating localized sound field carrying sound data to a selected spatial position being in close vicinity to the user U. for forming local audible sound field near the spatial position. Alternatively, or additionally, one or more of the transducers are capable of emitting sound signals in the audible frequency regime to thereby generate conventional audio at their respective coverage zones. Accordingly, in such embodiments the system  1000  is capable of performing some required actions privately (e.g. by private transmission of ultrasound signals by which local audible sound field with said sound data is formed in close vicinity of the user) such that persons other than the user are not aware of the action performed by the system; or performing such required actions publicly (e.g. public transmission of conventional audible sound signals carrying the sound data of the action to a region of the user). Accordingly, in some implementations of the system  1000 , the audio session manager  570 , and more specifically the action decider  572 , may be for example adapted to determine a type of privacy for the transmission of the sound data or other content to the user. The type of privacy being indicative of whether the transmission is to be conducted as:
         A. Private transmission of ultrasound signals by which local audible sound field with said sound data is formed in close vicinity of said user; or   B. public transmission audible sound signals with said sound data at a region of said user;       

     The decision about the type of privacy may be based on a user&#39;s specific request/indication (e.g. see gesture-responsive action a. above for switching from public to private communication mode); or it may be based on the decision/estimate of the artificial intelligence module of the action decider  572  about a type of privacy to be used in a given scenario (e.g. given user state). To this end, in embodiments where the action decider  572  includes an AI engine/module the AI engine is may be employed inter-alia for determining the type of privacy for communicating with the user at various scenarios. 
     Accordingly, in case the actions to be implemented by the system include content/notifications, which are to be provided to the user in audible form, the action decider  572  provides corresponding sound data to the output sound generator  600  along with data indicative of the type of privacy to use for the transmission of the sound data. In turn the output sound generator  600  is adapted to receive data indicative of said type of privacy of the transmission, and selectively operating at least one selected transducer for the transmission of the sound data according to said privacy type. 
     Alternatively or additionally, as indicated by the list UI output means (i) to (vi) above, other means such as haptic means and private displays may be used to implement certain actions with or without privacy. In case such means need to be used, the action decider  572  determines/selects which mean to use (based inter alia on the privacy properties thereof) and operates the selected mean with appropriate data/content fro performing the required action. 
     Thus the technique of the present invention providers a complete conversational AI solution for user, while exploiting the system ability to privately provide users with content they request (e.g. using the confined localized transmission of audible sound to the user&#39;s ear&#39;s, or when needed providing user with conventional public sound. 
     Various implementations and advantages of the technique of the present invention are further clarified in the following in relation to some example implementations:
         a. switching the system interaction with the user from public to private communication mode, and vice versa;   b. provision of specifically requested content, to the user utilizing auditory, visual or haptic forms;   c. provision of autonomously selected content (e.g. based on general request of the user) utilizing auditory, visual or haptic forms;   d. Activation of private or public notification or alert according to user-initiated schedule.   e. Activation of private or public notification or alert in response to certain identified user state;   f. Activation of private or public user authentication (e.g. in case the user is not authenticated by the system);       

     Examples of Action f. Above: User Authentication
         As indicated above, in some configuration, the gesture detection module may be used to detect one or more gestures associated with user identity, or to authenticate the user based on a combination of gestures. More specifically, one or more users may be each assigned with a unique gesture that allows the audio communication system to identify the user while simplify processing of input data. In an embodiment, the system  1000  (e.g. the gesture recognition) utilizes a certain user&#39;s body-pose identified by the gesture recognizer  550  as a ‘wake word’, which when detected, the system automatically unlocks for the specific individual user. The system may then communicate the fact that it is unlock to the specific individual user by through a private audio/haptic indication to the user.   In another embodiment, the system can be used for security identification where a user can be requested via the focused audio to perform a certain combination of gesture &amp; speech the user set as his own identification criteria, thereby ensuring a higher level of security. The identification can be used in-lieu of a password, pass-phrase or other biometric security.       

     Example of Action c. Above: Provision of Autonomously Selected Content
         In one possible embodiment, the user asks the system to tell them some jokes. The system samples a large database of jokes and uses estimates of the user&#39;s reaction to each joke to facilitate a refinement of the sampling algorithm. Over time, the jokes become progressively more tailored to the specific ‘humor profile’ of the user.       

     Examples of Action a. Above: Switching from Public to Private
         Two users are watching a sporting event on a shared TV and one user requests to receive updates on the status of a related, simultaneous sporting event. The system then requests a summary data stream using a cloud API from the related sporting event broadcaster. When key events occur in the related event, the system first verifies that the requesting user is still present and their current state. When appropriate, the system provides an update using spatially localized audio. Using this approach, two users are able to enjoy physical proximity while getting two distinct audio experiences. The system may optionally provide a haptic cue to the user and then wait until they look at the system before providing an localized audio response.   In an additional embodiment, a user engaging in an audible conversational interaction with a voice assistant uses a hand gesture to signify that they want to make the rest of the conversation private. The system switches from speaker-based audio feedback to focused audio feedback that only the user can hear.       

     Example of Action d. Above: Activation Notification According to User Initiated Schedule
         The user can ask the system to set a timer for 10 minutes while they cook. On every minute during the countdown, the system can spatially localize an audio announcement of the time remaining to the location of the user&#39;s head. When only one minute remains, the system would also provide a haptic sensation to ensure that the user knows that the time is almost elapsed.       

     Example of Action e. Above: Activation of Private or Public Notification or Alert in Response to Certain Identified User State:
         In a home security embodiment, the system can identify or receive indication the an important event such as a door or window opening in the middle of the night. The system can identify the location and state of the user (e.g. in bed, sleeping) and then provide a specific audio/haptic alert to ensure that the user responds to the event. In some embodiments, the system can further have a progressive alerting policy that provides distinct user-specific feedback depending on the nature of the event.   In a related embodiment, a home security system can prompt a user with a combination of private audio and haptic feedback as a portion of the authentication mechanism. A suitably enabled doorbell system could generate a one-time passcode for specific individuals that is delivered using private audio and haptics and require the user to enter a related code into the system&#39;s touch interface and/or audio sensors.       

     Turning back to the gesture detection module  550 , it should be noted that gesture detection module  550  may also be configured and operable for receiving data about user location from the user detection module  520  and receiving sensing data associated with the same location from the one or more TDSMs  110 , and/or from the microphone array  120 . The gesture detection module  550  is further configured to process the input data to identify whether one or more predefined gestures are performed by the user. Upon detecting one or more gestures, the gesture detection module  550  operates to generate and transmit one or more corresponding commands to the sound processor utility  600  for performing one or more corresponding actions. In some embodiments, the received sound analyzer  560  is configured to receive and analyze input vocal commands from a user in combination with the gesture module  550 . To achieve that the received sound analyzer  560  may include one or more natural language processing (NLP) modules  561 , which implement one or more language interpreting technique as generally known in the art, for deciphering of natural language user commands. More specifically, a user may provide vocal commands to the audio communication system while using natural language of choice. The received sound analyzer  560  may thus be configured and operable to separate/filter the user&#39;s voice from the surrounding sounds (e.g. optionally based on the location of the user of interest P as indicated above and/or based on the spectral content/color of the user&#39;s voice) and to analyze parts of the input vocal/voice data of the user (e.g. analyze the parts, which are indicated as vocal command(s) by the gesture detection module  550 ), to determine the actual commands the user P gives the system. Thus, this may be based on the free/natural language speech of the user and possibly also movement or other physical gestures of the user. In some additional embodiments, the received sound analyzer  560  may utilize one or more language processing techniques of a remote processing unit (e.g. cloud). To this end the control system  500  may transmit data indicative of the sound received by the audio input sensors  120  to a remote location for processing and receives analyzed data indicative of contents of the input signal. 
     In some configurations, the gesture detection module  550  may also be configured to operate as a wake-up module. In this case gesture detection module  550  is configured and operable to respond to communication session initiating command in the form of audible of movement gesture performed by a user. For example, such audible gesture may be configured to initiate a bilateral communication session directing a remote user (e.g. telephone conversation) in response to a keyword such as “CALL GEORGE”, or any other contact name, to locate George&#39;s contact info in a corresponding memory utility and to access the input/output utility to initiate an external call to George or any other indicated contact person. It should also be noted that a contact person may be present at the same space at the time, being in a different or the same connected region of the space (i.e. within line of sight or not). In this case, a command such as “CALL DAD” may operate the user detection module  520  to locate users within the space and operate the face recognition module  530  to identify a user indicated as “Dad”, e.g. with respect to the call requesting user, and to initiate a private bilateral communication session between the users. In such private bilateral communication session between two users, e.g. within different rooms, audio output of a first user is collected by a selected microphone array  120  of a first audio communication system  1000 , where the first user is located within coverage zone of the first system  1000 . The collected audio is transmitted electronically to a second audio communication system  1000  that operates to identify location of a second selected user (e.g. George, Dad) and to operate the corresponding selected transducer unit  100  to generate private audio signal around the ears of the second user. At the same time, audio generated by the second user is collected by the corresponding second audio communication system  1000  and transmitted similarly to be heard by the first user. 
     As indicated above, and illustrated in  FIG. 1B , the system  1000  may be deployed in one or more connected spaces (such as in plurality of rooms of the apartment APT, and possibly also deployed in additional one or more disconnected/remote locations/spaces such as the vehicle VCL. Accordingly the system  1000  may be configured and operable for providing seamless communication between users regardless of physical distance between them. To this end, the remote locations (e.g. the apartment APT the vehicle VCL) may be connected to similar control systems (e.g.  500  and  500 ′) and may use, or be connected with, a common management server  700  who forms external data/audio connection/communication between control systems (e.g.  500  and  500 ′). To this end, the management server  700  may be located remotely from one or more of the control systems connected thereto, and may include an audio session manager  570  which manages the audio sessions of the users while also tracking the locations of the users as they move between areas/spaces controlled by the different control systems, so as to seamlessly transfer the management and operation of the audio sessions to the respective control system  500  or  500 ′ as the user enters the zone/space controlled thereby. 
     To this end, the management server  700  is actually connected to one or more end units, e.g.  200 ,  200 ′, whereby each end units controls a certain one or more connected spaces (e.g. rooms) and manages the audio sessions of users within these spaces. Each such end unit may be configured and operable as described above with reference to  FIGS. 1B and 1C  and may typically include at least one of transducer array unit  100 , TDSM unit  110  and microphone unit  120 . The remote connection between the end units, e.g.  200 ,  200 ′, and the management server  700  may utilize any known connection technique including, but not limited to, network connection, optical fiber optic, etc. 
     The one or more remote location may include one or more corresponding additional audio server unit providing sub-central processing scheme, a plurality of additional audio server units providing distributed management, or connected remotely to a single audio server unit to provide central management configuration. For example, the processing unit  500  may be connected to external server (cloud) where all of the users&#39; locations are gathered. When, at a certain place, the user detection module  520  of the processing unit  500  recognizes a selected user, it reports to the external server  700  of its location, thus diverting all communications (internal or external) to that specific processing unit  500 , to be directed to the selected user/recipient. 
     Also, as indicated above, the control/processing unit  500  may generally include an orientation detection module  540  configured to determined orientation of a user&#39;s head in accordance with input sensory data from the one or more TDSMs  110  and the 3D model of the sensing volume. The orientation detection module  540  is thus configured for determining orientation of at least one of the user&#39;s head or ear(s) with respect to location of the TDSM  110 , and preferably with respect to the transducer unit  100 . The orientation detection module  540  may thus generate an indication whether at least one of the at least one user&#39;s ears being within line of sight with the at least one transducer unit. Based on the determined location and orientation of the user&#39;s ears, the processing unit  500  may utilize a direction module, not specifically shown, configured for receiving data indicative of location and orientation of the user&#39;s head/ear(s) and processing the data in accordance with 3D model of the space to determine one or more optimized trajectories for sound transmission from one or more selected transducer units to the user&#39;s head/ear(s). 
     Generally, an optimized trajectory may be a direct line of sight from a selected transducer to the user&#39;s head/ear(s). However, when such direct line of sight does not exist, or exists but based on a transducer unit located at a relatively large distance with respect to other trajectories, reflection of acoustic signals or other techniques may be used. More specifically, when a direct line of sight between a transducer unit and the user&#39;s head/ears cannot be determined, the processing unit  500  may operate the sound processor utility  600  to direct the local sound region at a point within line of sight of the selected transducer unit  100 , which is as close as possible to the user&#39;s ears. 
     It should be noted that generally the private sound region may be defined as a region where outside of it the sound intensity is reduced by, e.g. 30 dB, thus, the sound may still be noticeable at very close proximity to the selected region and enable the user to identify the sound and possibly move around to a better listening location. 
     Alternatively or additionally, in case an optimized trajectory in the form of a direct line of sight between a transducer unit  100  and the user&#39;s head P is not found, the sound processing utility  600  and more specifically the transducer selector module  620  thereof may operate to determine an indirect path between one of the transducers  100  to the user&#39;s head P. Such an indirect path may be include a direct path form the one or more of the transducers  100  to one or more acoustically reflective objects OBJ located in the vicinity of the user P. To this end the transducers selector  620  may receive the 3D model of the spaces monitored by the TDSMs which is generated by the pattern recognition engine/utility  515  and utilize that model to determine one or more objects OBJ which are located near the user (e.g. within a predetermined distance therefrom), and which may have sufficient acoustic reflectivity that can be exploited for indirect transmission of sounds to the user P. To this end, in some embodiments the pattern recognition module  515  also includes an object classifier (not specifically shown) that is configured and operable to classify recognized objects in to their respective types and associate each object type with a certain nominal acoustical reflection/absorbance parameters (e.g. acoustic spectrum of reflectance/absorbance/scattering) which typically depend on the structure and materials of the objects. Accordingly, in determining an indirect path (also referred to herein as a reflective-type trajectory) from a selected transducer unit to the user&#39;s head/ears, the transducer selector  620  may simulate/calculate the attenuation of the sound field (possibly calculate a per frequency attenuation profile) for each candidate path between a transducer  100 —a reflective object OBJ—the user P. To this end, the transducer selector  620  may be configured and operable for employing any number of acoustic simulation/estimation techniques to estimate the acoustic field attenuation per each given candidate transducer  100  and candidate reflective object OBJ, based on the distance from the candidate transducer  100  to the object OBJ and from the object OBJ to the user (e.g. which may be indicated by the 3D model) and based on the acoustical reflection parameters of the object OBJ. A person of ordinary skill in the art would readily appreciate the various possible techniques which can be implemented by the transducers selector  620  to estimate the acoustic field attenuation associated with each indirect/reflection path to the user. Among the possibly several candidate indirect paths (possibly involving different transducers and/or different objects) the transducers selector  620  selects the path(s) having the least acoustic attenuation and/or the least distortive acoustic attenuation, and thereby selects one and possibly more than one transducers to be used for in direct transmission acoustic signal to the user P via reflection from the object(s) in the space. To this end, in case there is no short enough direct path between any of the transducers  100  to user P, the transducers selector  620  utilizes the 3D model of the space (region of interest) and to determine an indirect (reflection based) sound trajectory the includes a reflection from a surface of an object (e.g. wall) of an towards the hidden user&#39;s ear. 
     Since the reflection may cause reduction in acoustic intensity and greater spreading of the signal, a trajectory including a single reflection is typically preferred over greater number of reflections. 
     In case the one or more transducer units  100  is used to generate sonar-like sensing data for forming the 3D model, the model may also include certain indications about acoustic reflections from the surfaces. Accordingly the object classifier may utilize such sonar-like sensing data to determine the acoustic reflection properties of the objects in the space. 
     As indicated above, the audio communication system according to the present invention may utilize centralized or distributed management. This is exemplified in  FIG. 2  illustrating an audio communication system  2000  including central control unit  500 A (acting as an audio communication server) connectable to a plurality of transducer units, transducers  100   a ,  100   b  and  100   c  are exemplified herein, and to a plurality of TDSM units,  110   a  and  110   b  are exemplified. Each of the transducer units ( 100   a ,  100   b  or  100   c ) may be mounted at a selected location in a space to enable transmission of acoustic signals forming local sound region at a selected location within a respective coverage zone (CZa, CZb or CZc as exemplified in the figure) as describe below with reference to  FIG. 5 . Additionally, the TDSM units,  110   a  or  11   b , are configured to be mounted at selected location within a space to provide sensory data indicative of respective sensing volumes (SVa and SVb as exemplified in the figure). Additionally, the system may include one or more microphone arrays  120  employed at selected locations and configured to provide data about acoustic signals collected from the space where the system is employed. 
     It should be noted that the sensing volumes of the different TDSM units  110  and the coverage zones of the transducer units  100  may be separate physical units or packed together in a single common physical unit. Additionally, the transducer array units  100  and the TDSM units  110  are preferably mounted such that the total space where the system is mounted is covered by coverage zones CZ of the transducer array units and sensing volumes SV of the TDSM units. Preferably, each transducer array unit  100  is paired with a corresponding TDSM unit  110 , to cover a common region being both within coverage zone of the transducer unit  100  and sensing volume of the TDSM unit  110 . 
     The transducer units  100  and the TDSM units  110  are commonly connectable to one or more centralized control unit  500   a  configured to manage input and output data and communication of the system as described above with reference to control unit  500  in  FIG. 1A . The control unit  500   a  is generally configured to act as an audio communication server configured for managing private audio communication between different users within the space where the system is employed and input and output communication using a communication network (e.g. telephone communication, internet communication etc.). 
     The control unit  500   a  generally includes at least a mapping module  510 , user detection module  520  and sound processor utility  600 . Generally, the control unit may also include, or be connectable to, one or more memory utilities and input and output communication ports. 
     The mapping module  510  is configured as described above to receive input sensing data from the TDSM units  110 , and in some configurations from the transducer units  100  and to provide mapping data indicative of a relation between the sensing volumes and the coverage zones. Such mapping data may also include the 3D model of the space where the system is employed. To this end the mapping module may generally obtain calibration data (e.g. automatically generated and/or manually inputted) about locations in the space where the different transducer units  100  and TDSM units  110  are deployed, and preferably a schematic map of the space itself. 
     The user detection module  520  is connectable to the three dimensional sensor modules (TDSM units)  110  for receiving sensory data indicative of objects&#39; arrangement and movement thereof in the corresponding sensing volumes, SVa and SVb as shown in the figure. The user detection module  520  is further configured and operable for processing the input sensory data to determine existence and spatial location of one or more user&#39;s in the corresponding space. As indicated above with reference to  FIG. 1A , the user detection module  520  may also include a face recognition module  530 , orientation detection module  540  and gesture detection module  550 . Typically, in some embodiments of the invention, the user detection module is operable to receive input command indicating a specific user, and to process sensory data from the plurality of TDSM units  110  to determine if the specific user is located within any of the sensing volumes covered by the system, identify the user by facial or other recognizable features and determine spatial location of the user, suitable for transmission of local, private, sound region that will be heard by the user. Preferably, the user detection module is capable to provide spatial coordinates indicative of location of at least one of the user&#39;s head/ears to enable accurate and direct transmission of sound to the user&#39;s ears. 
     The sound processor utility  600  is connectable to the transducer units  100  and adapted to receive sound data indicative of sound to be transmitted to a selected user and to operate a selected transducer unit to generate and transmit acoustic signals to thereby play the desired sound signal to the user privately. 
     In this connection, the sound processor utility  600  may be responsive to input data indicative of a selected user designated as target for a message and data indicative of the acoustic content of a message to be played to the user. In response to such input instructions, the sound processor utility may communicate with the user detection module  520  for spatial location of the specified user; receive data about corresponding transducer covering the determined spatial location from the mapping module  510 ; and operate the selected transducer  100  to transmit suitable acoustic signals to thereby form a private sound region carrying the message to the specified spatial location. As also indicate, above, the user detection module  520 , and the orientation detection module thereof, may preferably provide data indicative of location of at least one or the user&#39;s ears to provide accurate and private audio communication. 
     Additionally, and as indicated above, according to some embodiments the control system  500  may also include an received sound analyzer  560  configured and operable to be connected to one or more microphone arrays  120  employed in the covered region/space and for receiving input audio data from the microphone arrays  120  to enable bilateral communication session. Generally, the received sound analyzer  560  is process input audio signals received from one or more selected microphone arrays  120  in the connected sites and determine acoustic data generated by a selected user, e.g. a user initiating or participating in a communication session. To this end the one or more microphone arrays  120  may be configured as directional microphone array using time or phased delay to differentiate input acoustic data based on location of source thereof. Additionally or alternatively, the sound processor utility may utilize ultra-sonic reflections received by a transducer unit  100  transmitting acoustic signals to a user, and correlate the ultra-sonic reflections with audible signals collected by a microphone arrays  120  to determine sound portions associated with the specific user. 
     Generally it should be noted that the one or more microphone units  120  are typically connectable to the control/processing unit  500   a  (or  500  as exemplified in  FIG. 1A ) to provide audio input data. Such audio input data may be associated with one or more vocal gestures and/or be a portion of bilateral ongoing communication session. To this end the user detection module  520  as well as the sound processing utility  600  are typically configured and operable for receiving input audio data and for determining one or more vocal gestures and/or operating to process content of the data for operational instructions and/or relating to the input audio data as part of ongoing communication session and transmitting the data to a local or remote recipient. 
     As indicated above, the audio communication system described herein utilizes one or more control units ( 500  or  500   a ) connectable with one or more transducer units  100 , TDSM units  110  and possibly one or more microphone arrays/units  120  to provide private, hand free communication management within certain space (region of interest). In this connection reference is made to  FIG. 3  illustrating an end unit  200  configured for use in the audio communication system described above. The end unit generally includes a transducer array unit  100 , three dimensional sensing module  110  and may include a microphone array unit  120 . Additionally, the end unit  200  typically also include an input/output module  130  configured for providing input and output communication between the end unit and a control unit  500  connected thereto. 
     As indicated above, the transducer array unit  100  may typically include an array of transducer elements  105 , each configured to emit ultra-sound signals. The transducer array unit  100  may typically also include a sound generating controller  108  configured to determine appropriate signal structure and phase relation between signals emitted from the different transducer elements  105 . The transducer array unit  100  is configured and operable for generating local sound region at a desired location. To this end, the sound generating controller  108  is configured to drive the different transducer elements  105  of the array  100  to transmit selected ultra-sonic signals with selected phase difference between the transducer elements  105  to form a focused ultra-sonic beam to a selected location (point in space) determined in accordance with the phase differences between emitted signals. The ultra-sonic signal may be formed with two or more selected main frequencies with selected amplitude and phase structure. The two or more frequencies and the amplitude and phase structure thereof is selected to provide air borne nonlinear demodulation of the sound waves of the signal forming desired audible sound wave at a desired location. 
     Technically, the different base frequencies within the ultra-sonic beam demodulated due to pressure waves&#39; interaction in nonlinear medium (e.g. air, gas filled volume, water). More specifically, when the signal contains acoustic waves with two (or more) difference frequencies f 1  and f 2 , the nonlinear of the air demodulate the signal and produces frequencies that are integer multiplicities of f 1  and f 2 , sum of f 1 +f 2 , and difference between f 1  and f 2 . Using appropriately ultra-sonic frequencies provides that the difference between the frequencies is within the audible acoustic spectrum and include the desired audible acoustic signal. 
     The transmitted acoustic signals therefore are configured to generate local audible region (a region at which sound is heard privately) at a selected location, preferably at close vicinity the user&#39;s head. To this end, based on data from the user detection module  520 , the sound processor utility  600  determines the location of the head of the selected user. Then, as described above, utilizing mapping data from the mapping module  510 , the transducer selector  620  selects a selected transducer (possibly more than one transducer; e.g.  100   a ,  100   b ,  100   c  in  FIG. 2 , or combination thereof), to be operated to transmit sound directly or indirectly to the user&#39;s head/ears. 
     Then the selected transducer is operated in the manner described above for generating and transmitting a localized sound field carrying the desired sound data towards close vicinity of the user&#39;s head/ear(s). 
     Reference is made now to  FIGS. 4A and 4B , whereby  FIG. 4A  is a flow chart showing a method  4000  carried out according to an embodiments of the present invention for transmitting localized (confined) sound field towards the head of the user P, and  FIG. 4B  is a schematic illustration of the localized (confined sound field generated in the vicinity or the user&#39;s head). In operation  4010  the system, typically the user detection module  520  locate the users in the region of interest. In operation  4020  the face recognition module  530 , identifies and locates the head of the user of interest (e.g. user P) within the region of interest. In operation  4050  the system. typically the transducer selector  620  determines/selects a suitable transducer unit  100  that can be used to transmit sound signals/field directly or indirectly towards the user&#39;s head so as to generate a localized confined sound field in the vicinity of (e.g. at least partially enclosing) the head of the user P. In operation  4060 , the audio signal generator  630  is operated to generate operative sound encoding signals which can be used to operate the selected transducer  100  to transduce the localized/confined sound field in the vicinity of the user. To this end, in operation  4060  the sound from ultrasound (US) signal generator  632  is operated to determine the ultrasound content of the signals, which after non-linear interaction with the medium (e.g. the air) near the user, will generate/form an audible sound field that can be heard by the user. Also in operation  4060  the beam-former  634  is operated to generate the specific signals per each transducing element  105  of the selected transducer  100  such that the in accordance phase delays and the different spectral contend provided to each transducing element  105 , one or more ultrasonic beams (typically two or more) of predetermined shape(s) and direction(s) will be transmitted by the selected transducer  100  towards the user, whereby the ultrasonic spectral contents of such beam is such that after interacting with the medium (e.g. air) in the vicinity of the user, they will create an audible sound field carrying the desired sound data to the user&#39;s ears. Accordingly the transducer array unit  100  is operated to generate, using phase array beam forming techniques, an acoustic beam of ultra sound frequencies. 
     As shown in  FIG. 4B , this technique effectively creates an acoustic bright zone BZ in which the transmitted signals form audible sound field that can be heard by the user. The acoustic bright zone BZ is typically selected to be near the user&#39;s head (e.g. surrounding all or part of the user&#39;s head). The bright zone BZ is surrounded from its sides and back by dark zones DZ in which the transmitted signal may still form some audible acoustic wave, but with sound pressure level (SPL) which is sufficiently low so as not to be heard, or hardly heard, by the human ears. Accordingly the acoustic bright zone BZ actually defines a sound bubble region in which the audible acoustic field carrying desired sound data can be heard and out of which the acoustic field is not audible (e.g. as it is in the ultrasonic frequency band) and practically can&#39;t be heard. Indeed, in some implementation, there may also be generated a private zone PZ acoustic region which includes a certain region in between the bright zone and the transducer array unit  100  at which the ultra-sonic acoustic waves form some level of audible sound. Typically, this private zone extends for a certain distance (e.g. in the range between few centimeters and few decimeters) from the user P towards the transducer  100 . To this end it should be understood the zone behind the user (e.g. from the user to the direction away from the transducer  100 ) is a dark zone at which audible sound is not heard. 
     Additionally or alternatively, upon selection of the transducer unit  100  (e.g. any one of the transducers  100   a  to  100   m ) to be operated for transmitting the audio field to the user P, the transducer selector module  620  verifies that there are no other users in the propagation path of the audio field towards the specified user P (namely that there are no other users in the area between the selected transducer and the user P). In that case the audio level in the “dark zone” DZ between the selected transducer and the user is less importance, as long as its SPL is lower than the SPL in the bright zone BZ. Typically, indeed the SPL at this region is significantly lower than in the bright zone BZ. It should be noted that in case there are other users in the region between the selected transducer and the user P, then the transducer selector module  620  may select a different one of the transducers  100  for projecting the audio field to the user, and/or determines a reflective (indirect) propagation path for the audio field to the user (e.g. via reflections through OBJ). 
     Generally, it should be understood that when using the private audio technique of the present invention, the SPL outside the bright zone BZ (namely in the private and dark zones PZ and DZ surrounding the bright zone in any direction) is at least 20 db lower than the ZPL at the bright zone BZ. 
       FIG. 4B  shows an example of generation of a confined sound field surrounding the user&#39;s head (e.g. the entire head of the user). However, in some implementations/embodiments of the system of the present invention, it is more preferable to generate a smaller sound bubbles (smaller localized audible sound fields) which are confined only at regions surrounding one or both of the user&#39;s ears, but not surrounding the entire head of the user P. This may have several advantages. For once, generating audible sound from ultrasound may generally not be highly energetically efficient. That is whereby large percentage of the energy is spent on generation of ultrasonic sound fields, only small percentage of the energy of the ultrasonic fields undergoes the non-linear interaction which converts them to audible sound. Therefore, in order to reduce the required power/energy for generating the desired audible sound field to the user, and accordingly possibly also reduce the complexity and cost of the transducers used, it is preferable to generate smaller localized audible sound field bubbles that are confined only near/about the user&#39;s ears. Additional advantage relates to the ability to provide the user with binaural (e.g. stereophonic) sound data which is generally possible when transmitting different sound content to the different ears. Yet additionally, generation of spatially extended confined sound bubbles (e.g. extending over several tens of centimeters so as to enclose the entire user head) with no/reduced distortions may in some cases be more complex (e.g. more computationally intensive and/or require larger number of transducer elements  105 ) than the generation of smaller sound bubbles (e.g. of only several centimeters to one or two decimeters) which are only confined about the user&#39;s ear(s). Therefore, for one or more of the above reasons it is in many cases preferable to generate smaller localized sound field only focused in the vicinity of the user&#39;s ear(s). 
     However, conventional face recognition and/or face features analysis techniques are generally incapable and/or are deficient in their ability to accurately, continuously and reliably identifying and determining the location of a user&#39;s ears. This may be due to several reasons: (i) the user ears may be hidden/partially behind/below his hair; (ii) the user may be viewed from its profile thereby hiding one of his ears; and/or (iii) some of the available techniques are also completely avoiding detecting of the users ears, possibly due to the complex 3D shape of the ear. 
     To this end, according some embodiments the method  4000  also includes operation  4030  which is carried out to determine the location of the ear(s) (one or both of the ears) of the user P so that a confined localized audible sound field, smaller than that required for the entire head, can be generated near one or both of the user&#39;s P ears.  FIG. 4C  is a schematic illustration showing in self-explanatory manner the smaller bright zones BZ 1  and BZ 2  of the confined audible sound (bubble), which are generated by the transducer  100  in the vicinity of the user&#39;s ears. As shown, outside these bright zones BZ 1  and BZ 2  there is dark zone at which audible sound cannot be practically heard. In some embodiments, optionally at a certain distance (e.g. of few decimeters) extending from the bright zones BZ 1  and BZ 2  to the transducer  100 , there exists a so called private zones PZ 1  and PZ 2  at which audible sound can be heard but not clearly and/or with low intensity. 
       FIG. 4D  is a flow chart showing in more details the method for implementing operation  4030  of method  4000  for determining the location of the user&#39;s P ears. In some embodiments of the present invention the face recognition module  530  is configured and operable for carrying/implementing method  4030  to spatially locate and track the location(s) of the user&#39;s ear(s), while optionally by utilizing pattern recognition capabilities of the pattern recognition engine  515 . 
     In operation  4032  the face recognition module  530  operates to apply facial/pattern recognition to the sensory data obtained from the TDSM (e.g. to the image data or the 3D model, and/or the composite image and/or the 3D image, obtained from the TDSM). To this end, facial recognition may be implemented according to any known in the art technique. 
     In operation  4034  the face recognition module  530  determines whether based on the facial recognition, the ears of the user P can be recognized in the image. In case the ears of the user P are recognizable in the image, the face recognition module  530  continues to operation  4036  where it determines ears location in the space covered by the TDSM based on the their location in the image. More specifically, in this case based on 3D data from the TDSM′ image/model, the face recognition module  530  determines the 3D position of the ear(s) in the sensing volume covered by the TDSM. 
     Optionally, in case the ears of the user P are recognizable in the image, the face recognition module  530  proceeds to carry out operation  4038  for generating/updating a personal head model of the user P. For instance, in operation  4038  the face recognition module  530  may determine/estimate the facial model of the user P based on the image by carrying out steps a, b and c as follows:
         (a) operate facial recognition scheme/process to determine the locations of additional facial landmarks (e.g. other than the ears) in the user&#39;s face. For example, determining the locations of the nose bridge and the eyes and the distances between them.   (b) process the locations of the ear(s) and the locations of the additional facial landmarks in the user&#39;s P to obtain an estimate of certain personal anthropometric relations of the user&#39;s face. Accordingly a personal head model including for example certain predetermined anthropometric relations of the user&#39;s face which associate the location of the user&#39;s ears to other facial landmarks is determined.   (c) generate/update personal head model based on the anthropometric relations of the user&#39;s face as obtained for the current image of the user&#39;s face. In this regards it should be noted that the face recognition module may include or be associated with facial data reference data-storage (not specifically shown) which is configured and operable for storing personal head models of users. The users for which facial models are stored may include be registered users (e.g. regular users which are known/registered in the system) and for which facial model data may be stored permanently. Optionally the facial reference data-storage also stores facial models of transient users (not registered in the system), for at least as long as such users are engaged with a communication session and/or as long as such users are within the spaces covered by the TDSMs of the system (e.g. the facial models for transient users may be deleted when the users leave the spaces covered by the system and/or when after their communication sessions terminate). Accordingly, before storing the personal head model determines in (b) the face recognition module  530  first checks to see if a matching model already exist in the facial reference data storage. If not the model is stored as a new model. However if the matching model already exists, the existing model is updated based on the data obtained from the present image, namely based on the newly estimated model. In order to improve the accuracy of the stored personal head model of the user P during time, the updating may be performed while utilizing certain filtering schemes such as Kalman filter and/or PID filter, which allow the data obtained from plurality of measurements (e.g. from the plurality of images of the user) to be converged to form higher accuracy models.       

     It should be noted that operation  4038  is optional, and may be carried out in order to complete/update the head model based on the location of the ears and other facial landmarks in the image. 
     In case operation  4034  finds that the ears of the user P cannot be recognized in the image, the continues to operation  4040 , where it determines whether the facial data reference data-storage of the face recognition module  530  already stores a personal head model of the user&#39;s P face. 
     In case the reference data-storage has a personal head model of the user P, the face recognition module  530  proceeds to carry out operation  4042  to determine the location of the ear(s) of the user P in the space, based on the personal head model of the user P and the location in the space of other facial landmarks identified in the image of the user obtained from the TDSM. 
     Otherwise, in case the reference data-storage does not include personal head model of the user P, the face recognition module  530  proceeds to carry out operation  4044  where it determines the location of the ear(s) of the user P in the space, based on a statistical anthropometric modelling approach. More specifically in this case the face recognition module  530  determines the locations of one or more facial landmarks of the user in the space monitored by the TDSMs (e.g. by processing the TDSM&#39;s image), and utilizes one or more statistically stable anthropometric relations between the location of the ears of users relative to the locations of other facial landmarks on order to obtain an estimate of the location of the user&#39;s P ears. To this end, in  4044 , the detected facial landmarks in the image and corresponding anthropometric data is essentially used in  4044  to deduct the location of the ears. 
     Additionally, in  4044  the personal head model may be constructed or further updated based for example on the facial landmarks of eyes, nose etc′ of the user. Accordingly the head model is further updated as additional images of the user P are obtained and processed (see operation  4046 ). In this regards, even if in the ears are not visible in the image, the model may be updated by adjusting the locations of the facial landmarks of the model in accordance with the detected locations of the corresponding facial landmarks in the current image. 
     In this regards, the statistical anthropometric modelling approach implemented by the face recognition module  530  of the present invention may include one or more of the following:
         (a) An average face proportions approach. This is a simplified approach based on the fact that a typical/average human face typically follow certain proportion relations such as those described for example in http://dhs.dearbornschools.org/wp-content/uploads/sites/625/2014/03/facial-proportions-worksheet.pdf. To this end, in some embodiments the face recognition module  530  utilizes the fact that the inter-pupillary-distance (IPD) is on average about ⅗ of the head width. Accordingly, by applying facial recognition to determine the locations in the TDSM images of the facial landmarks corresponding to the user&#39;s pupils, the head dimensions and accordingly the ears positions can be estimated.   (b) Anthropometric modelling approach—This approach is based on available anthropometric statistical data obtained from measurements of plurality of users. To this end, in some embodiments the face recognition module  530  utilizes statistical anthropometric databases, such as available at https://www.facebase.org/facial_norms/ to derive empirical multi-variate functional relations between ears position of a user and various facial landmarks. This approach is sensitive to subtle relations in human subgroups and can account for instance for the combined effect of various parameters, such as wide nose with circular face etc. Accordingly, using the visible facial land marks in the image of the user P, the face recognition module  530  can determine their shape (e.g. wide nose) and accordingly classify the user to a certain subgroup of humans such as Asian, Caucasian or others, Then, based on the classified subgroup, the face recognition module  530  obtains the relevant accurate anthropometric relations for the user P.       

     Accordingly, as indicated in operation  4046 , the face recognition module  530  repeats the method  4000  per each image obtained from the TDSM(s) which includes the user P. Accordingly, typically after one or more images are captured, typically the ears of the user are reveled and personal head model of the user P is constructed (e.g. from scratch even if such model was not apriority included in the facial reference database. More specifically, in many cases the ears are exposed and visible to the camera, especially when following the head movement over time, when the user naturally turns the head. Direct detection of ears position is thus available and the personal anthropometric relations between facial landmarks and ears position, for the specific user P can be determined accurately. 
     Thus during the repeated analysis of images of the user&#39;s face, method  4000  provides for further updating such personal head model of the user to improve its accuracy. In other words, as more information and statistics is accumulated over time a more accurate and stable estimates personal head model of the user P is obtained. Accordingly, in some embodiments of the present invention method  4000  is implemented and used for locating and tracking the ears of the user of interest P. In turn the output sound generator module  600  generates the confined/private audible sound field near the user ears, and thereby efficiently transmits audible sound to the user P. 
     To this end, the acoustic signal forms a localized audible sound field defining a private zone confined to the vicinity of the region between the designated location Zo and the acoustic transducer system  10 . The area includes one or more bright zone regions where clearly audible and comprehendible audible sound is produced. Outside of the bright zone BZ a dark zone region is defined in which the sound is either not audible to the human ear, or its content cannot be clearly comprehended. 
     Thus, turning back to  FIG. 1A , it should be noted that according to some embodiments of the present invention the output sound generator module  600  is adapted to operate the one or more transducer units  100  to transduce acoustic signals to be received/heard by one or both ears of the user P, and possibly of additional users. More specifically, the user detection module  520  detects the ear(s) of the user P in the manner described above, and the transducer selector  620  determines/selects the transducer(s)  100  by which sound should be transmitted to each one of the ear(s). As indicated above, the transducer selector  620  determines the propagation path (direct or indirect path) of the acoustic signals from the selected transducer(s) to the respective ear(s) of the user P towards which the acoustic signals should be transmitted by the selected transducer(s). Accordingly the sound from ultra-sound signal generator  632  and the beam-former  634  are configured and operable to generate signals for operating the selected transducer array(s) to transduce ultrasonic acoustic signals which when undergo non-linear interaction with the medium (e.g. air) in their propagation path towards the user, form very small audible sound bubble(s) in the vicinity of (e.g. surrounding) one or both of the user&#39;s P ears. To this end, the size of the audible sound bubble of each ear may be as small as few millimeters in diameter and may be typically in the range of few millimeters to few centimeters, so as not to surround the entire head of the user P 
     The technique above allows the system  1000  to provide individual audible sound to each one of the user&#39;s P ears separately. This, in turn permits to privately transmit binaural sound to the user P. To this end, it should be understood that the same of different transducer(s)  100  may be selected (by the transducer selector  620 ) and operated to transmit the sound to the different ears of the user P. For example, different transducers  100  may be selected in case the right ear of the user is in the line of sight of one transducer (e.g.  100   a ) and the left ear is in the line of sight of another transducer (e.g.  100   b ). Accordingly, also the distance between the transducer(s)  100  and the left and right ears of the user may be different (e.g. this may be due to the difference in distance between the transducer(s) and the ears and/or as a results of the user of reflective propagation paths to one or both of the ears). Therefore, in such embodiments the may be a need to adjust the balance of the audible binaural sound provided to the user (namely properly adjust the balance between the right and left volumes of the audible sound bubbles the user hears). Indeed, transmission the sound to the left and right ears with the same intensity may yield unbalanced right-left audible sound to the user, due to the difference in the propagation paths between the respective transducer(s) and the right and left ears of the user P. Therefore, according to some embodiments, after the transducer selector  620  selects the respective one or more transducer(s)  100  that would be used to transmit sounds to the ears of the user P and after it determines their respective direct and/or indirect propagation paths to the respective ears, the transducer selector  620  further determines the attenuation levels of the transmitted acoustic signals/fields along the propagation paths to each ear of the user P. Accordingly, the transducer selector  620  provides the sound from ultrasound signal generator  632  with data indicative of the attenuation levels of the audible fields during their propagation to the user&#39;s ear(s). In turn the ultrasound signal generator  632  utilizes the received attenuation levels in order to adjust the transmission amplitudes of the ultrasound signals so as to obtain at least one of the following:
         (1) maintain a predetermined a right-left balance (e.g. equalized balance and/or user-adjusted balance) between the volume of the audible sound heard by the right and left ears of the user P; and   (2) provide the user with a timely continuous/smooth volume while the user may move through the space(s) covered by the system  1000  and while during this movement, different traducers may be switched to serving the user while being possibly at different distances from the user&#39;s ears.       

     Reference is now made to  FIG. 5  illustrating a system for audio communication  3000  according to some embodiments of the invention, employed in partially connected site with a space (region of interest ROI). In this example the ROI may be an apartment, office space or any other desired location. To provide coverage of the ROI, a plurality of end units (EU 1 , EU 2 , EU 3  and EU 4  in this example) are employed at selected location within the ROI. The end units generally include a transducer array unit  100 , TDSM unit  110  and possibly microphone array  120 , and are generally similar to the end unit  200  shown in  FIG. 3  or to distributed management communication system  1000  exemplified in  FIG. 1 . The different end units (e.g. EU 1 ) may be mounted on a wall, a ceiling, or any other surface, or be standing units, and configured to cover a corresponding coverage zone, which preferably aligns or mostly aligns with sensing volume of the TDSM unit of the end unit when used. 
     In this example, the audio communication system  3000  is configured as centrally controlled system and includes a control unit/audio server  5000 . The audio server  5000  may include one or more of the above described modules, including mapping module, user detection module and sound processor utility. As indicated above, the control unit  5000  is configured to respond to request to initiate communication session (either unilateral or bilateral) and manage ongoing communication session providing private sound region to the one or more users communicating. As indicated above, a communication session may be unilateral (the system transmits selected sound to a user) or bilateral (the system also collects sound from the user for processing or transmitting corresponding data to another user/system). 
     In this connection, reference is made to  FIG. 6  illustrating schematically an audio communication server  6000  configured and operable for operating a plurality of one or more transducer array units in combination with sensing modules to provide private and hand free audio communication within a region of interest. The server  6000  may be used as central control unit (e.g. control unit  500   a  or  5000  in  FIGS. 2 and 5 ) connectable to a plurality of distributed end units including transducer array units, TDSM units and microphone units; or it may be configured as an integral part of an audio communication system as exemplified in  FIG. 1 , in which the end unit  200  and the processing utility are packed in a single unit (single box). Generally the audio communication server  6000  may be a standalone server configured for connecting to a plurality of end units  200  as described above with reference to  FIG. 3 . Alternatively or additionally, in some embodiments, the audio communication server  6000  may be configured with one or more integral end units  200  while being connectable to one or more additional end units  200  as the case may be. 
     The audio server system  6000  generally includes one or more processing utilities  6010 , memory utility  720  and input/output controller  730 . It should however be noted that the server system  6000  may typically be configured as a computerized system and/or may include additional modules/units that are not specifically shown here. Also it should be noted that the internal arrangement of the units/modules/utilities of the server system may vary from the specific example described herein. 
     The input/output controller  730  is configured for connecting to a plurality of end units each including at least one of transducer array unit, TDSM unit and microphone array. Typically, some of the end units may be configured as described in  FIG. 3  above providing a single physical unit including transducer array unit, TDSM and microphone array. Generally, the input/output controller  730  enables communication with one or more selected end units using generally known techniques of network communication. 
     The one or more processing utilities  6010  typically include a mapping module  510 , user detection module  520 , sound processing module  600  as described above, further the one or more processing utilities  6010  may also include an external management server  700 , a response detection module  571  and a privileges module  580 . 
     Generally, as indicated above, the mapping module  510  is configured for providing calibration data about arrangement of transducer units and TDSM units within the ROI. The calibration data may be pre-stored or automatically generated. In some embodiments, the mapping module  510  is configured and operable to receive sensory data from the plurality of TDSM units, and in some embodiments from the transducer array units and input data about system employment in the region of interest, and to process the data for generating a 3D mapping model of the region of interest. The 3D model typically includes structure of the ROI, coverage regions of the different transducer unit and TDSM units, and data indicative of relatively stationary objects in the ROI. In some configurations, the 3D model may also include data about acoustic reflection and absorption properties of different surfaces in the ROI as detected by the different transducer array units. The 3D model is typically stored in the memory utility  720  and may be updated periodically or in response to one or more predetermined triggers. 
     The user detection module  520  is configured and operable to receive input data about a user to be detected, and to receive input data from the TDSM units about users within the ROI to thereby locate the desired user and determine spatial coordinates thereof. In some embodiments, the user detection module  520  is configured to determine spatial coordinates associated with location of the user&#39;s ears. Additionally, or alternatively, the user detection module  520  is configured and operable to be responsive to commands provided by one or more users in the ROI and generate corresponding indication to the sound processing utility  600 . Generally, as indicated above, the user detection module may include, or be associated with, one or more sub modules including face recognition module  530 , orientation detection module  540  and gesture detection module  550 . 
     As indicated above, the face recognition module  530  is configured and operable for receiving input sensory data indicative of one or more users, and preferably of faces of the users, and data about user identity that may be presorted in the memory utility, and for processing the sensory data to thereby determine identity of one or more users. To this end the face recognition module  530  may utilize one or more face recognition techniques as well as pre-stored data about one or more identities of registered users. 
     The orientation detection module  540  is configured to determine orientation of a detected user&#39;s head and location of the user&#39;s ears. To this end, the orientation detection module is configured and operable for receiving input sensory data and for processing the input data as indicated above using one or more image processing techniques as generally known in the art. 
     The gesture detection module  550  is configured and operable to be responsive to one or more movement and/or vocal gestures from one or more users in the ROI and for generating an appropriate notification including data about the requesting user and location thereof, and the requested command. Generally, as indicated above, the gesture detection module  550  is configured to be responsive to a plurality of predetermined vocal or movement related gestures, the gestures are assigned with corresponding commands associated with one or more action to be performed by the system. For example, a user may request “call home” requesting that the system will operate to determine the user&#39;s identity, search for the user&#39;s home phone number, and utilize the external management server  700  to communication with the phone connection to initiate the call. Additional commands may be associated with control of operation of different external systems, such as “turn on TV” command associated with identifying the TV unit within the region where the user is located and turn it on, or with communication with other users. In some embodiments, the predetermine commands may include operation commands associated with system management such as request to increase volume, access data, etc. 
     The sound processing utility  600  is configured and operable to be connectable to the one or more transducer units and to operate one or more selected transducer units to generate selected acoustic signal and provide desired private sound to one or more selected users. Generally, the sound processing utility is configured for receiving or generating data about audio signal to be transmitted to one or more selected users, and to receive data about the user&#39;s location from the user detection module  520 . The sound processing utility may also receive data about 3D model of the ROI from the mapping module  510  (or from the memory utility  720 ) and determine one or more selected transducer units suitable for transmitting the desired acoustic signal to the selected user(s). 
     The sound processing utility  600  may also be configured and operable for analyzing input and/or output audio data. For example the sound processing utility  600  may be configured to receive data indicative of audio/vocal user instructions from the gesture detection module, to thereby analyze the input data with one or more speech (free speech) recognition technique and generate corresponding instructions. 
     In some configurations, the sound processing utility  600  may also be configure for using one or more cloud processing techniques. The sound processing utility  600  may thus be configured to transmit data indicative of audio signal to be processed to a remote processing utility through the external management server  700 . The data is processed and analyzed by a remote server and corresponding analyzed data is transmitted back to the audio communication server  6000  and the sound processing utility  600  thereof. 
     Typically, the sound processing utility  600  may be configured and operable for processing input data and generate corresponding output data and to perform one or more of the following processing types: translation of input data from one language to one or more other languages, analyzing input data to determine one or more technical instructions therein, analyze input data to provide filtered audio data (e.g. filter out noise), process input data to vary one or more properties thereof (e.g. increase/decrease volume, speed, etc.) and other processing techniques as the case may be. The processing may be performed by the sound processing utility  600  and/or partially performed at a remote processing server as described above. 
     As indicated above the sound processing utility  600  may determine one or more possible line of sights between selected transducer array units and the user&#39; ears. Typically, the sound processing unit may be configured to prefer transmission of acoustic signals along clear line of sight; however in some embodiment the sound processing utility may utilize a reflective type line of sight, in which the acoustic signals undergo one or more reflections from one or more surfaces before reaching the user&#39;s location. As also indicated above, the sound processing utility  600  is typically configured to operate one or more selected transducer array units for generating private sound region at selected location as described above and in patent publications WO 2014076707 and WO 2014147625 assigned to the assignee of the present application. 
     Additionally, according to some embodiments, the sound processing utility  600  may include, or be associated with, an audio input module  610 . The audio input module may be connectable to one or more microphone array units employed in the ROI and to receive acoustic input data associated with user&#39;s generated sound. Such acoustic input data may be associated with vocal command related gestures as well as user response as a part of bilateral communication session. The audio input module  610  may be configured to receive input data associated with acoustic audible signals collected by the one or more microphone array units. Generally, the microphone array units may be configured to also provide data associated with location of source of the collected acoustic audible signals. This may be provided by proper selection of the microphone array unit, e.g. units configured as phase array of microphone elements or directional microphone elements. Additionally in some configurations, the collected acoustic audible signals may be processed in accordance with ultra-sonic signals collected by one or more selected transducer arrays to determine correlation between ultra-sonic reflection from the user and audible input from the user and filter out noised from the periphery of the user. More specifically, the transducer array is operated to focus a single ultrasonic wave on the users face based on the user location provided by the user detection module  520  in accordance with sensory data from the corresponding TDSM units. The transducer unit may also collect data about reflection of the ultra-sonic signals reflected from the recipient&#39;s (user) face. Movements of the user&#39;s face, such as mouth movements, create small variations to the reflected waves due to Doppler Effect. These variations are generally correlated to audio signals generated by the user and may be processed in combination with input audio signals to filter out surrounding noise and improve signal to noise ratio. 
     As indicated above, the audio communication server  6000 , and processing utility  6010  thereof, may also include response detection module  571  and/or privileges module  580 . The response detection module  571  is generally configured and operable to determine data indicative of user&#39;s reaction to input signal transmitted thereto. More specifically, the response detection module  571  may be configured and operable to receive data about one or more signals transmitted to a user from the sound processing utility  600 , and sensory data of the user from the user detection module  520  and/or one or more corresponding TDSM of end units, and to correlate the input data to determine user response to the signal. Generally, a user&#39;s response may be associated with movement pattern, change in facial expression, generating sound etc. 
     Such response data may be collected for further processing and analysis, or transmitted to external system, e.g. the system that initially generated the signal transmitted to the user, as indication of receipt. Such response data may be used for example, for parent to identify if their kids have responded to messages sent to them, for advertisement analysis and other uses. 
     The user privilege module  580  is configured for receiving data about one or more users generating one or more commands to the system, and data about the requested command and for determining of the requesting user has privileges right for initiating the command. As indicated above, the audio communication system may provide private sound to one or more different users. Additionally, vocal and movement gestures may vary between users, as well as access and management privileges. To this end the privilege module  580  may correlate data about user identity and requested action and determine, based on pre-stored privileges map, if the user has the right to initiate the requested action or not, or to specifically identify the requested action in accordance with identity of the requesting user. It should be noted that user identity may be determined in accordance with input sensory data associated with the user, or in accordance with vocal or gesture type password provided by the user. To this end the privilege module  580  may be configured and operable for receiving input data indicative of one or more keywords provided by the user and determine if user identity is sufficiently determined. Additionally the privilege module  580  may be configured and operable for allowing or preventing access to external actions performed by the external management server  700  as the case may be. 
     The processing utility may also include an external management server  700  configured to mitigate communication between the audio communication server  6000  and external system as the case may be. For example, the external management server  700  may be connectable to a communication network, telephone line, different electronic systems such as home appliances, remote (cloud) server etc. The external management server  700  is configured to initiate actions such as providing notification to specific users, e.g. washing machine finished cycle, manage input calls from outside sources, as well as to transmit data from the system or the users in the ROI to any desired connected external system. 
     In this connection, reference is made to  FIGS. 7, 8, 9 and 10 , exemplifying methods of operation of the audio communication system according to the present invention for several exemplary actions. In  FIG. 7  the system operates to transmit certain signal to a selected user; in  FIG. 8  the system provides seamless communication session to moving user; in  FIG. 9  the system response to user initiated action; and in  FIG. 10  the system determines user&#39;s response to input signal. 
     As shown in  FIG. 7 , the system receives a request for transmitting message to a user  7010 , either from a different user, the processing utility (e.g. management data signal) or from an external system through the external management server. The request typically includes data about one or more messages to be sent and data about a user/recipient to the message. Received requests may generally be pre-processed to determine one or more request properties such as urgency, request type etc. Further, the pre-processing may include verifying if outstanding user instructions exist regarding corresponding requests (e.g. user wishes to receive requests only at certain hours, user wishes to receive requests in bulks, or a number of requests within certain time period etc.). Once the request is allowed to be transmitted to the user, the communication system operated the user detection module to located users within the ROI  7020 , and to identify the selected recipient between the users  7030 . If the requested user in not found, a response notification may be sent to the source requesting the signal transmission, the system may select a default user or utilize connection to one or more speakers and play general audible message to all users. If the user is located, the user detection module identifies spatial coordinates of the user  7040  and the sound processing utility may determine preferred transducer array unit for transmitting the signal  7050 . The sound processing utility can then transmit data indicative of the signal and the spatial location of the user to the selected transducer array unit for transmission of the signal to the user  7060 . It should be noted that such a signal may initiate a bilateral communication session such as telephone conversation. Alternatively, such signal may be informative only and merely indicate user reaction to determine if the user actually received the signal or not. 
       FIG. 8  exemplifies a technique for providing seamless and hand free communication to users according to the present invention. As shown when a user is in ongoing communication session  8010  (e.g. telephone conversation with a third party, or listening to music) the system marks the user is active and follows user&#39;s location  8020 . Additionally, the system collects audio signals generated by the user to be transmitted to the third party and therefore maintaining communication. The user detection module follows location data of the user  8020  and generated indication to the sound processing utility if the user is near an edge of coverage zone of the transducer unit used  8030 . When the user is close to edge of the coverage zone, the sound processing utility determines and identifies an additional transducer array unit having coverage zone suitable to provide communication to the user&#39;s location  8040  and determines measure data indicative of suitability of transducer array unit to a specific location and orientation of the user. When the additional transducer array is preferred over the currently used one the sound processing utility shifts communication session to the newly selected transducer array  8050  to continue ongoing communication session  8060 . 
     Additionally,  FIG. 9  exemplifies system operation in response to a user&#39;s initiated action. In this connection, the user detection module is generally actively receiving sensory data from the ROI for processing the sensory data and determining locations of users. The gesture detection module received data about user&#39;s movement or audible signals generated thereby and determines if a recognizable gesture is performed by a user  9010 . When a gesture is recognized, the face detection module may be operable to determine user&#39;s identity  9020  and the gesture module determines the corresponding command associated with the gesture  9030 . Generally, the user&#39;s identity is compared with the user privileges for the requested action  9040 . If the user has not privileges, the system may provide him with appropriate notification. The requested action may be provided  9050  by transmitting requested data to a remote location through the external management server, or initiating communication session or any other action specified. As indicated above, an action may be a request to communication with specific other user, being within the ROI (internal private communication session) or remote (e.g. telephone call type communication session, or communication with remote ROI connected to the same or similar audio communication system). Additionally, or alternatively, such action may be associated with operation of third party systems such as turning on the water heater, opening front door, turning volume of audio system up or down etc. 
       FIG. 10  exemplifies operational technique for determining data about user response to input messages transmitted thereto. When an acoustic message is transmitted to a user  10010 , the user detection module and the response detection module may be operated to receive input sensory data indicative of the user  10020 . The received sensory data in processed  10030  in correlation with data about the transmitted signal to identify correlations between the user sensory data and the signal sent thereto. Such correlation may be associated with content of the transmitted signal however the correlation may also be temporal correlation. If the response detection module determined that the correlation is higher than a corresponding predetermined threshold, user response is determined  10040  and appropriate indication is generated  10050 . The indication may be transmitted to the signal source as reading receipt, and/or stored for further processing locally or remotely. 
     Thus, the technique of the present invention provides unilateral and bilateral audio communication transmitted directly to selected user&#39;s ears while allowing only the selected user to hear the signals clearly. It should however be noted that the system and technique of the present invention as described herein may also be configured to selectively utilize one or more audible speakers for providing public sound within the ROI. This may be performed when a specific desired user is not found in the ROI, or in order to provide clear signal to a plurality of users. Additionally, the technique and the privilege module thereof may also be used to request users for proof of their identity such as request for a password or security question to determine user&#39;s identity. 
     Further, the technique and system of the invention as described above may be operable for providing various types of communication sessions based on the above described building blocks. Such communication sessions may be between a user and system control (e.g. the sound processing utility), between two or more user&#39;s communication through the system (located in different coverage zones (e.g. rooms)) within the ROI, or between one or more user and an external third party. Such external third party may be a remote user utilizing similar or different audio communication system (e.g. telephone conversation) or one or more other systems capable of receiving and/or transmitting appropriate commands. 
     Those skilled in the art will readily appreciate that various modifications and changes can be applied to the embodiments of the invention as hereinbefore described without departing from its scope defined in and by the appended claims.