Abstract:
A method of providing an improved learning environment in a classroom setting area in which at least one human listener is attempting to focus on at least one speech sound source in the presence of at least one distracting sound source is disclosed. At least one electrical sound masking signal is generated by at least one sound masking signal generator as output, received by at least one system controller, and then provided to one or more loudspeaker assemblies. At least one acoustic sound masking signal corresponding to the at least one electrical sound masking signal is emitted by the one or more loudspeaker assemblies into the classroom setting area, providing an essentially uniform level of acoustic sound masking signal, thus improving the ability of the human listener(s) to focus on the intended speech sound source in the presence of the distracting sound source.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. application Ser. No. 12/518,460 filed Jun. 10, 2009, which application claims the priority of U.S. Provisional Patent Application No. 60/874,818 filed Dec. 14, 2006, the whole of both of which are incorporated by reference herein. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    Voice reinforcement systems (also called “voice lift” systems) are known that may be employed to improve communication by increasing the intelligibility of human speech. Such voice lift systems may be deployed in classrooms, offices, conference rooms, auditoriums, or any other suitable venue for small or large gatherings to assure that listeners can both hear the voice and understand the speech of a talker at all listener locations within the venue. For example, a simple voice lift system for use in an office or conference room may include at least one microphone, a mixer/amplifier sub-system, and at least one loudspeaker. In one exemplary application, the office or conference room in which the voice lift system is deployed may be partitioned into a plurality of zones, and at least one microphone and at least one loudspeaker may be disposed in each one of the zones. Further, to assure that listeners located within each of the zones can hear and understand a talker situated within any one of the zones, the mixer/amplifier sub-system may selectively direct voice signals generated by the microphone disposed within the talker&#39;s zone to the loudspeakers associated with one or more of the other zones, while at least partially limiting the voice signals provided to the loudspeakers within the talker&#39;s zone. In this way, the simple voice lift system can enhance the ability of listeners to comprehend the talker&#39;s speech at the various zone locations within the office or conference room. 
         [0004]    The simple voice lift system described above has drawbacks, however, especially when it is deployed in an open-plan classroom or office environment. For example, in a large, open-plan classroom, the talker may be an instructor such as a teacher or a professor, and the listeners may be students listening to the instructor&#39;s lecture. Although the above-described voice lift system may be deployed in such a classroom environment to improve the intelligibility of the instructor&#39;s speech, unwanted sound resulting from student activity inside or outside of the classroom and/or other background or ambient noise may be generated at levels high enough to distract the student listeners from the instructor&#39;s lecture. 
         [0005]    It would therefore be desirable to have an improved system and method of providing sound reinforcement for use in a classroom, an office, a conference room, an auditorium, or any other suitable venue that allows listeners to hear and understand the voice of at least one talker with increased clarity and intelligibility at all listener locations. Such a system and method would allow a talker&#39;s voice to sound equally natural and equally intelligible at all of the listener locations. It would also be desirable to have a sound reinforcement system that provides the capability of reducing or eliminating unwanted sound including background or other ambient noise emanating from inside or outside of the venue in which the system is deployed, thereby allowing listeners at all of the listener locations to hear and understand the voice of a talker with less distraction. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    In accordance with the present invention, an improved system and method is disclosed for providing sound reinforcement in a classroom, an office, a conference room, an auditorium, or any other suitable venue. The presently disclosed system and method can be configured to provide a voice reinforcement (“voice lift”) function via a plurality of spatially distributed emitters (“loudspeakers”), thereby providing a more uniform sound field coverage and allowing a talker&#39;s voice to sound equally natural and equally intelligible at all listener locations within the venue of interest. The disclosed system and method can also be configured to provide a sound masking function, preferably via the same plurality of spatially distributed loudspeakers used for the voice lift function. In this way, more uniform levels of acoustic sound masking signals can be generated throughout the venue in which the system is deployed. 
         [0007]    In one embodiment, the presently disclosed sound reinforcement system includes a plurality of microphones, a receiver, a sound masking signal generator, a system controller, and a plurality of spatially distributed emitters (“loudspeakers”). Each of the microphones is operative to detect the speech of a talker, and to generate at least one voice signal corresponding to the detected speech. The voice signal generated by each microphone may be a wireless (e.g., infrared (IR) or radio frequency (RF)) voice signal, and the receiver may be a wireless (e.g., IR or RF) receiver operative to receive the wireless voice signals from the microphones. For example, when the disclosed sound reinforcement system is deployed in a classroom environment, one of the microphones may be worn by an instructor either on a lanyard, clipped as a lavaliere, or as a headset, while one or more of the other microphones may be of a hand-held type suitable for being passed from one student to another during periods of student participation. Further, the wireless receiver may be configured to be mountable to the ceiling to assure that the IR or RF signals generated by the microphones worn by the instructor and held by the students are received with minimal obstruction and/or interference. The sound masking signal generator is configured to store at least one set of information specifying at least one sound masking spectrum, and to generate at least one electrical sound masking signal having the sound masking spectrum specified by the stored set of information. The system controller is operative to receive the voice signals and the sound masking signal from the microphones and the sound masking signal generator, respectively, to provide the voice signals on at least one first channel, and to provide the sound masking signal on at least one second channel. Like the wireless receiver, the plurality of spatially distributed loudspeakers is configured to be mountable at the ceiling level. Each of the loudspeakers has a low directivity index, and is arranged to face downwardly from the ceiling. In addition, each of the loudspeakers can be configured to receive both the voice signals and the sound masking signal provided on the first channel and the second channel, respectively, and to emit acoustic voice and sound masking signals corresponding to the received voice and sound masking signals, respectively, simultaneously and directly into the venue in which the system is deployed. As a result, a more uniform sound field coverage for the acoustic voice signals, and more uniform levels of the acoustic sound masking signals, can be obtained throughout the venue of interest. 
         [0008]    In one embodiment, the system controller is operative both to adjust an output level of the sound masking to reduce the level of distraction from noise either inside or outside of the venue, and to adjust the acoustic voice signal based at least in part upon sound masking spectra of two or more mutually incoherent electrical sound masking signals to obtain at least one specified performance characteristic, e.g., a specified signal-to-noise ratio (SNR). 
         [0009]    The presently disclosed sound reinforcement system provides features that address the communication needs of individuals who gather to meet in small or large venues such as classrooms, offices, conference rooms, auditoriums, etc. For example, the plurality of spatially distributed loudspeakers has low voltage and power requirements and can be easily installed at the ceiling of the venue to provide distributed audio delivery and a more uniform sound field coverage, thereby allowing a reduced overall sound level for a given Articulation Index. Further, to mitigate delay-related phenomena caused by the Haas effect (also called the “precedence effect”) when the system is deployed in larger venues, the receiver can be configured to perform microphone localization processing, including calculating time delays to be applied to the voice signals generated by the talker&#39;s microphone based upon the relative distances between the microphone and the spatially distributed loudspeakers. As a result, the talker&#39;s voice can be made to have a more natural sound at all listener locations in the venue no matter where the talker is currently located. 
         [0010]    Moreover, when the disclosed sound reinforcement system is deployed in a classroom environment, the system can employ the sound masking function to reduce the actual or perceived level of student activity noise and/or background or ambient noise emanating from inside and/or outside of the classroom, thereby allowing the students concentrate on the teacher, to study, to take tests, and to perform group work with significantly less distraction. In addition, the receiver can be configured to receive voice input signals from the instructor and one or more of the students simultaneously, and the system controller can be configured to provide the voice signals of the instructor and students on respective channels for subsequent transmission as acoustic signals via the spatially distributed loudspeakers. The receiver can also be configured to incorporate one or more internal antennas, and/or to interface with one or more external antennas, to obtain spatial diversity or any other desired RF diversity reception for reducing the occurrence of drop-outs as the instructor speaks into the microphone while moving about the classroom. Rechargeable battery packs and/or docking stations may also be provided for the instructor and student microphones. 
         [0011]    Still further, the system controller can be configured to receive audio input signals from one or more local and/or external audio sources such as a compact disk (CD) player, a digital video disk (DVD) player, or a personal computer (PC), and/or one or more local and/or external paging sources. In the event it is desired to receive an audio input signal from an audio source external to the venue in which the system is deployed, the system controller can be provided with an analog or digital connection to any suitable local or wide area network or the Internet, and the desired audio input can be received over the network connection. For example, if the network connection is operative to connect the system controller to the Internet, then any suitable voice over Internet protocol (VoIP) may be employed to receive the desired audio input. The network connection may also be employed to connect the system controller to an external receiver over the VoIP network to provide near-instantaneous notification of an emergency or other event occurring within the venue. To that end, one or more of the microphones, such as the instructor&#39;s microphone in a classroom environment, may be provided with a pushbutton for remotely signaling the receiver of an actual or perceived emergency, and, in response to the signaling from the microphone, the receiver may provide an emergency signal to the system controller, causing a network connection between the controller and the external receiver to be automatically established over the VoIP network. In addition, the system controller can be configured to receive VoIP-based paging, alone or in combination with VoIP-based voice transmission, to enable emergency-mode VoIP telephony. For example, the system controller may employ VoIP paging to provide point-to-server communication of emergency or other information for subsequent re-distribution. The system controller may also employ VoIP voice transmission to provide point-to-point communication of emergency or other information between multiple venues in which like systems are deployed. 
         [0012]    Other features, functions, and aspects of the invention will be evident from the Detailed Description of the Invention that follows. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0013]    The invention will be more fully understood with reference to the following Detailed Description of the Invention in conjunction with the drawings of which: 
           [0014]      FIG. 1  is a block diagram of a sound reinforcement system according to the present invention; 
           [0015]      FIG. 2  is a block diagram illustrating a representative layout of spatially distributed loudspeakers included in the system of  FIG. 1 , for use in describing a microphone localization processing application; 
           [0016]      FIG. 3  is a block diagram of a VoIP emergency or other event notification system incorporating the system of  FIG. 1 ; 
           [0017]      FIG. 4  is a block diagram of a VoIP point-to-point communication system incorporating the system of  FIG. 1 ; 
           [0018]      FIG. 5  is a block diagram illustrating the system of  FIG. 1  employed in a VoIP pod-casting application; and 
           [0019]      FIG. 6  is a block diagram illustrating the system of  FIG. 1  employed in a VoIP paging application. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The entire disclosures of U.S. application Ser. No. 12/518,460 filed Jun. 10, 2009, entitled DISTRIBUTED EMITTER VOICE LIFT SYSTEM, and U.S. Provisional Patent Application No. 60/874,818 filed Dec. 14, 2006, entitled DISTRIBUTED EMITTER VOICE LIFT SYSTEM WITH OPTIONAL SOUND MASKING, are incorporated herein by reference. 
         [0021]    An improved system and method is disclosed for providing sound reinforcement in a classroom, an office, a conference room, an auditorium, or any other suitable venue. The presently disclosed system and method can provide voice reinforcement (“voice lift”) functionality via a plurality of spatially distributed emitters (“loudspeakers”), providing a more uniform sound field coverage and allowing a talker&#39;s voice to sound equally natural and equally intelligible at all listener locations. The disclosed system and method can also provide sound masking functionality via the same plurality of spatially distributed loudspeakers used for the voice lift function, generating more uniform levels of acoustic sound masking signals throughout the venue in which the system is deployed. 
         [0022]      FIG. 1  depicts an illustrative embodiment of a sound reinforcement system  100 , in accordance with the present invention. In the illustrated embodiment, the sound reinforcement system  100  includes a plurality of microphones  102   a,    102   b,  at least one receiver  104 , at least one sound masking signal generator  106 , at least one system controller  108 , and a plurality of emitters (“loudspeakers”)  112   a,    112   b,    112   c,    112   d,    112   e,    112   f  spatially distributed within a venue  110 . Each of the microphones  102   a,    102   b  is operative to detect the speech of a human operator (the “talker”), to generate at least one voice signal corresponding to the detected speech, and to provide the voice signals to the receiver  104 . As shown in  FIG. 1 , the voice signals generated by the microphones  102   a,    102   b  correspond to wireless (e.g., infrared (IR) or radio frequency (RF)) voice signals  103 , and therefore the receiver  104  is configured as a wireless (e.g., IR or RF) receiver. It should be appreciated, however, that the voice signals generated by the microphones  102   a,    102   b  may alternatively be provided to the receiver  104  via wired connections. For example, the voice signals  103  may be provided to the receiver  104  using Institute of Electrical and Electronics Engineers (IEEE) 802.11, Bluetooth, or any other suitable wireless or wired communications protocol. In one embodiment, the receiver  104  is configured to be ceiling mountable to assure that the IR or RF signals  103  generated by the microphones  102   a,    102   b  are received with minimal obstruction and/or interference. The receiver  104  provides electrical voice signals  105  corresponding to the wireless voice signals  103  generated by the microphones  102   a,    102   b  to the system controller  108 . 
         [0023]    As shown in  FIG. 1 , the sound masking signal generator  106  is configured to generate at least one electrical sound masking signal  107  having a specified sound masking spectrum, and to provide the sound masking signal  107  to the system controller  108 , which receives the voice signals  105  and the sound masking signal  107  from the receiver  104  and the sound masking signal generator  106 , respectively. In one embodiment, the system controller  108  provides the voice signals  105  and the sound masking signal  107  to the six spatially distributed loudspeakers  112   a - 112   f  over multiple channels  109 . For example, the system controller  108  may provide the voice signals on at least one first channel and the sound masking signal on at least one second channel, and then provide the voice and sound masking signals to the loudspeakers  112   a - 112   f  over the respective channels  109 . Like the receiver  104 , each of the spatially distributed loudspeakers  112   a - 112   f  is configured to be ceiling mountable. In one embodiment, each of the loudspeakers  112   a - 112   f  has a low directivity index, and is arranged to face downwardly from the ceiling, thereby allowing the respective loudspeaker to emit acoustic voice and sound masking signals simultaneously in one or more direct paths to the ears of individuals (the “listeners”) located in the venue  110  in which the system  100  is deployed. As a result, a more uniform sound field coverage for the acoustic voice signals, and more uniform levels of the acoustic sound masking signals, can be obtained throughout the venue  110 . In an alternative embodiment, the plurality of loudspeakers can include two or more sets of loudspeakers, in which at least one set of loudspeakers is used to emit the acoustic voice signals and at least one other set of loudspeakers is used to emit the acoustic sound masking signals. 
         [0024]    In one embodiment, the sound masking signal generator  106  is configured to store at least one set of information specifying at least one sound masking spectrum, and to generate at least one electrical sound masking signal having the sound masking spectrum specified by the stored set of information. The sound masking signal generator  106  is therefore like the sound masking signal generator described in U.S. Pat. No. 7,194,094 (the &#39;094 patent) issued Mar. 20, 2007 entitled SOUND MASKING SYSTEM and assigned to the same assignee of the present invention, the entire disclosure of which is incorporated herein by reference. Specifically, the sound masking signal generator  106  operates to provide two or more channels of mutually incoherent electrical sound masking signals having temporally random signals with frequency characteristics within the specified sound masking spectrum. In one embodiment, the predetermined sound masking spectrum is designed with less “roll off” in sound intensity in high frequency components, e.g., frequency components above approximately 1250 Hz, to provide superior sound masking in an open plan venue such as an open plan classroom or office. 
         [0025]    As described above, each of the spatially distributed loudspeakers  112   a - 112   f  is configured to be ceiling mountable, to have a low directivity index, and to be arranged to face downwardly from the ceiling to allow the respective loudspeaker to emit the acoustic voice and sound masking signals simultaneously in one or more direct paths to the ears of the listeners located in the venue  110 . In the illustrated embodiment, each of the loudspeakers  112   a - 112   f  is like the loudspeaker assembly described in the above-referenced &#39;094 patent, having the low directivity index and being disposable within an aperture in the ceiling. As shown in  FIG. 1 , the six loudspeakers  112   a - 112   f  are disposed in a 3-by-2 arrangement spaced apart from one another by distances d 1 , d 2  to provide sufficient overlap in the acoustic voice and sound masking signals emitted by adjacent loudspeakers, thereby producing a uniform sound field coverage and uniform levels of acoustic sound masking signals throughout the venue  110 . It should be appreciated, however, that any other suitable number of loudspeakers in any other suitable arrangement may alternatively be employed. For example, the loudspeakers  112   a - 112   f  can be wired directly to the system controller  108 , or daisy chained from one loudspeaker to the next via wired connections. 
         [0026]    As shown in  FIG. 1 , the sound reinforcement system  100  further includes a remote control unit  114 , an external audio source  116 , a network  118 , a server  120 , and a database  122 . In the illustrated embodiment, the remote control unit  114  is configured to use IR, RF, or any other suitable wireless signals  115  to transmit data and/or commands to the system controller  108  for controlling the levels of one or both of the acoustic voice signals and the acoustic sound masking signals emitted by the loudspeakers  112   a - 112   f  in the venue  110 . The external audio source  116  is configured to provide additional audio input signals  117  to the system controller  108  for subsequent transmission in the venue  110  by the loudspeakers  112   a - 112   f.  For example, the external audio source  116  may be a compact disk (CD) player, a digital video disk (DVD) player, a personal computer (PC), a source of paging signals, or any other suitable audio source. The system controller  108  is configured to be communicably connectable to the network  118  via a network connection  119 . For example, the network  118  may include one or more of a local area network (LAN), a wide area network (WAN), the Internet, or any other suitable network. The system controller  108  is operative to communicate over the network  118  with the server  120 , which can include or be externally connectable to the database  122 . In one embodiment, the server  120  operates in conjunction with the database  122  as a database server to provide a structured collection of data files in the MP3 format or any other suitable file format for storing digital audio data. 
         [0027]    In an illustrative mode of operation, the sound reinforcement system  100  is configured to provide a voice reinforcement (“voice lift”) function in a classroom environment. To that end, one of the microphones  102   a,    102   b  may be designed to be worn by a classroom instructor either on a lanyard, clipped as a lavaliere, or as a headset, and another one of the microphones  102   a,    102   b  may be designed as a hand-held type suitable for being passed from one student to another during periods of student participation. The system controller  108  receives the voice signals  105  corresponding to the speech detected by the respective instructor and student microphones, and optionally any additional audio input signals  117  that the instructor may provide via a CD player, a DVD player, a PC, etc. In one embodiment, the voice signals  105  and the additional audio input signals  117  are provided to the system controller  108  simultaneously. The system controller  108  amplifies and processes the voice and other audio input signals  105 ,  117 , as appropriate, for subsequent distribution in the venue  110 , i.e., the classroom, via the loudspeakers  112   a - 112   f.    
         [0028]    The sound reinforcement system  100  provides features that address the communication needs of individuals who gather to meet in small or large venues such as instructors and students in a classroom environment. According to one such feature, the system controller  108  provides microphone localization processing to locate the microphone of the instructor, and to apply suitable delays to the voice and other audio signals provided to the spatially distributed loudspeakers  112   a - 112   f  based on the location of the instructor&#39;s microphone. As a result, the instructor&#39;s voice can be made to have a more natural sound at all student locations no matter where the instructor is currently located in the classroom. Such microphone localization processing is particularly useful in a large, open plan classroom environment. 
         [0029]      FIG. 2  depicts a representative layout of the spatially distributed loudspeakers  112   a - 112   f  for use in describing the microphone localization processing of the system controller  108  (see  FIG. 1 ). As shown in  FIG. 2 , the representative layout of the loudspeakers  112   a - 112   f  is like that depicted in  FIG. 1 , i.e., the six loudspeakers  112   a - 112   f  are disposed in a 3-by-2 arrangement spaced apart from one another by distances sufficient to provide a degree of overlap in the acoustic signals emitted by adjacent loudspeakers. The microphone localization processing can be employed to mitigate delay-related phenomena caused by the Haas effect (also called the “precedence effect”) when the system is deployed in a large venue such as a large, open plan classroom. 
         [0030]    Specifically, the system controller  108  performs microphone localization processing by calculating time delays to be applied to voice signals generated by the talker&#39;s microphone based upon the relative distances between the microphone and the respective loudspeakers spatially distributed throughout the venue. The system controller  108  typically calculates and applies such time delays when the venue is large enough to have listener locations where the observed difference between the arrival time of speech via the amplified signal path through the loudspeakers, and the arrival time of the same speech via the direct propagation signal path from the talker, exceeds approximately 20 msec. By tracking the talker&#39;s microphone location and applying the calculated time delays to the amplified signals, the speech emanating from the loudspeakers can be made to sound more natural at all listener locations. Applying the calculated time delays to the amplified signals also allows the listeners to locate the talker more easily. For example, in a classroom environment, students located at the rear of the classroom will be able to locate an instructor lecturing at the front of the classroom more easily because the sound of the instructor&#39;s voice emanating from the loudspeakers will be delayed, thereby causing the amplified sound from the loudspeakers to reach the students at substantially the same time as the sound of the instructor&#39;s unamplified voice. 
         [0031]    To calculate the appropriate amount of time delay to be applied to the amplified signals, the location of the talker&#39;s microphone, e.g., the instructor&#39;s microphone  102   a,  is estimated relative to the locations of the loudspeakers  112   a - 112   f  spatially distributed in the venue  110 , e.g., the classroom. As shown in  FIG. 2 , the exemplary venue  110  is partitioned into a plurality of zones  1 ,  2 ,  3  such that the loudspeakers  112   e - 112   f  are disposed in zone  1 , the loudspeakers  112   a,    112   d  are disposed in zone  2 , and the loudspeakers  112   b - 112   c  are disposed in zone  3 . Further, in this example, the instructor&#39;s microphone  102   a  is approximately centrally located in the classroom within zone  2 . Next, the time delays to be applied to the amplified sound emanating from the loudspeakers  112   a - 112   f  are calculated based on the time required for sound to travel from the location of the instructor&#39;s microphone  102   a  to the locations of the loudspeakers  112   a - 112   f  in the respective zones  1 ,  2 ,  3 . In one embodiment, the system controller  108  can apply the calculated time delays to the amplified signals by digitizing the voice signals  105  provided by the receiver  104 , buffering the digitized voice signals, and sampling the buffered signals at the calculated time delays. For example, a first time delay may be applied to the sound emanating from the loudspeakers  112   e - 112   f  in zone  1  and a second time delay may be applied to the sound emanating from the loudspeakers  112   b - 112   c  in zone  3 , while no time delay is applied to the sound emanating from the loudspeakers  112   a,    112   d  in zone  2  where the instructor&#39;s microphone  102   a  is located. 
         [0032]    In one embodiment, the location of the instructor&#39;s microphone  102   a  in the venue  110 , e.g., the classroom, is estimated by using a wavefront curvature technique. To employ the wavefront curvature technique, both the microphone  102   a  and the receiver  104  may be implemented as IR devices. For example, the IR receiver  104  may be configured as a two dimensional array of IR point sensors. By measuring the time delay of the IR signals generated by the microphone  102   a  between the IR point sensors of the two dimensional array, such as by cross-correlation of the IR sensor outputs, the curvature of the arriving IR wavefront, the direction of the microphone  102   a  relative to the receiver  104 , and the distance between the microphone  102   a  and the receiver  104  can be estimated. Using the estimated direction and distance of the microphone  102   a  relative to the receiver  104  and the known locations of the loudspeakers  112   a - 112   f  in the venue  110 , the distances between the microphone  102   a  and the respective loudspeakers  112   a - 112   f  can be determined. The appropriate time delays to be applied to the sound emanating from the loudspeakers  112   a - 112   f  can then be calculated based on the distances between the microphone  102   a  and the respective loudspeakers  112   a - 112   f.    
         [0033]    According to another feature, the sound reinforcement system  100  of  FIG. 1  can be incorporated for use in a VoIP emergency or other event notification system, as illustrated in  FIG. 3 . As shown in  FIG. 3 , a sound reinforcement system  300  deployed in a classroom environment can be communicably connected to a school or campus emergency response center via a network  318 . The sound reinforcement system  300  includes at least one microphone  302 , a system controller  308 , at least one loudspeaker  312 , at least one optional ear-bud device  326 , and an emergency on/off switch  324  for enabling the emergency or other event notification functionality. The microphone  302  is communicably connected to a VoIP encoder/decoder  308 . 1  and a voice lift processor  308 . 2  contained in the system controller  308 . The emergency on/off switch  324  is also communicably connected to the VoIP encoder/decoder  308 . 1 , which in turn is communicably connectable to the ear-bud device  326  via a Bluetooth transmitter  308 . 3  contained in the system controller  308 . As further shown in  FIG. 3 , the school or campus emergency response center includes an emergency processor  328  containing an alert processor  330 , a VoIP encoder/decoder  332 , and a server  320 , an alert display  334 , at least one microphone  336 , and at least one audio output  338 . The system controller  308  within the sound reinforcement system  300  can communicate with the emergency processor  328  over the network  318 . In addition, the alert processor  330  can provide alert outputs for display on the alert display  334 , and the VoIP encoder/decoder  332  can receive input signals and provide output signals from/to the microphone  336  and the audio output  338 , respectively. 
         [0034]    Accordingly, if an emergency occurs in the classroom, then the network  318  connecting the sound reinforcement system  300  to the school/campus emergency response center can be used as a communications path to inform school officials and/or emergency responders of both the occurrence and the characteristics of the emergency. In one embodiment, the network  318  corresponds to a school/campus data network generally accessible from every classroom in the school or on the campus. The two-way VoIP capability provided over the network  318  allows both emergency signaling and voice communications between the sound reinforcement system  300  and the school/campus emergency response center. 
         [0035]    In one embodiment, such emergency communication is implemented at the classroom in three steps, specifically, (1) notifying the school/campus emergency response center of the emergency, (2) describing the emergency in detail to the emergency response center, and (3) responding to instructions from the emergency response center for mitigation of the emergency. For example, such emergency notification may be accomplished by activating a pushbutton or a series of pushbuttons on the emergency on/off switch  324 , which may be located on the lavaliere microphone, on one of the hand-held microphones, or on the voice lift unit itself, or by providing speech recognition in the system controller  108 . Upon activating the emergency notifying signal, the time and location of the emergency is determined and recorded at the server  320  and subsequently routed to the emergency responders. Subsequent speech further describing the nature of the emergency, provided via the microphone  302 , can also be recorded at the server  320  and routed to the emergency responders. Upon receipt of the time, location, and description of the emergency, the emergency responders can, should the situation require it, provide information to an instructor alone through the ear-bud device  326 . The emergency responders can also activate emergency paging in the classroom and/or on a wider basis (e.g., building-wide or campus-wide), and initiate a two-way dialog with the individuals in the classroom over the network  318  for implementing possible emergency mitigation scenarios. 
         [0036]    According to still another feature, the sound reinforcement system  100  of  FIG. 1  can be incorporated for use in a VoIP point-to-point communication system, as illustrated in  FIG. 4 . As shown in  FIG. 4 , a plurality of sound reinforcement systems  400   a,    400   b,    400   c,    400   d  can be deployed in multiple classrooms, respectively, either in a school or on a campus. Further, each of the sound reinforcement systems  400   a - 400   d  is communicably connected to a server  420  via a local network  418 . 1 , which in turn is communicably connected to an external network  418 . 2  such as the Internet. Each of the systems  400   a - 400   d  includes at least one microphone  402 , a system controller  408 , a plurality of loudspeakers  412   a,    412   b,  and a network connection on/off switch  324  for enabling the VoIP point-to-point communication functionality. The microphone  402  is communicably connected to a VoIP encoder/decoder  408 . 1  and a voice lift processor  408 . 2  contained in the system controller  408 . The pod-cast on/off switch  424  is also communicably connected to the VoIP encoder/decoder  408 . 1 . Moreover, the system controller  408  within each sound reinforcement system  400   a - 400   d  can communicate with the server  420  over the local network  418 . 1 , and with a system  400   e  deployed in a remote classroom over the Internet  418 . 2 . In the illustrated embodiment, the system  400   e  is like the sound reinforcement systems  400   a - 400   d,  and is deployed in the remote classroom for enabling VoIP point-to-point communication, e.g., for remote learning, with the systems  400   a - 400   d  over the networks  418 . 1 - 418 . 2 . 
         [0037]    According to yet another feature, the sound reinforcement system  100  of  FIG. 1  can be employed in a VoIP pod-casting application, as illustrated in  FIG. 5 . As shown in  FIG. 5 , a sound reinforcement system  500  deployed in a classroom environment can be communicably connected to a local computer  540  and a server  520  via a local network  518 . 1 , and to a remote computer  542  via the local network  518 . 1  and an external network  518 . 2  such as the Internet. The sound reinforcement system  500  includes at least one microphone  502 , a system controller  508 , and an on/off switch  524  for enabling the VoIP pod-casting functionality. The microphone  502  is communicably connected to a VoIP encoder  508 . 1  contained in the system controller  508 . The pod-cast on/off switch  524  is also communicably connected to the VoIP encoder  508 . 1 , which in turn is connectable to the network  518 . 1 . In the VoIP pod-casting application, the capability of the system  500  to convert sounds into data packets allows archiving, storing, recovering, and replaying of those sounds concurrently or at some later time. For example, a lecture presented by an instructor, inclusive or exclusive of commentary from the student audience, may be recorded and archived, allowing others who may have missed the lecture, or may wish to revisit the lecture in the course of studying, to download and replay (e.g., pod-cast) the lecture at anytime in the future. In one embodiment, the system  500  can record digital audio, convert it to any suitable audio format, e.g., compressed (MP3, MP4, etc.) or uncompressed (WAV, etc.), and allow the instructor or others to catalog the recording appropriately. Such recording capability allows instructors and their supervisors to listen to the instructors’ lectures at some later time for the purpose of oversight and/or evaluation. In addition, the system  500  can be combined with a video recording/broadcasting system to create integrated audio/video broadcasts for use in remote learning. 
         [0038]    According to still yet another feature, the sound reinforcement system  100  of  FIG. 1  can be employed in a VoIP paging application, as illustrated in  FIG. 6 . As shown in  FIG. 6 , a sound reinforcement system  600  deployed in a classroom environment can be communicably connected to an administration center  616  via a local network  617 . The administration center  616  includes at least one microphone  616 . 1  and a VoIP paging interface  616 . 2 . The sound reinforcement system  600  includes a system controller  608 , a plurality of loudspeakers  612   a,    612   b,  and an optional ear-bud device  626 . The system controller  608  includes a VoIP decoder  608 . 1 , which is connected to the loudspeakers  612   a,    612   b.  In this example, the VoIP decoder  608 . 1  is also communicably connectable to the optional ear-bud device  626  via, e.g., a Bluetooth transmitter  608 . 2  contained in the system controller  608 . In the VoIP paging application, the system controller  608  converts voice signals generated by the microphone  616 . 1  into data packets, which may be received by any compatible VoIP device (e.g., a telephone, a PC, etc.) or by another installation of the sound reinforcement system (not shown). The sound corresponding to the data packets may subsequently be played through the spatially distributed loudspeakers  612   a,    612   b  disposed in one or more of the respective systems. 
         [0039]    Having described the above illustrative embodiments, other alternative embodiments or variations may be made. For example, the sound reinforcement system may be configured to distribute a voice lift function and a sound masking function via separate loudspeaker assembly systems; e.g., the sound masking signal may be distributed via upwardly facing loudspeakers in the ceiling plenum. The sound reinforcement system may be configured to include one or more personal receiver/amplifier/loudspeaker units for use by audibly challenged individuals in the venue in which the system is deployed. In addition, the sound reinforcement system may be configured to provide for the distribution of two or more channels of sound generated by one or more music sources. For example, the system can be configured to associate adjacent loudspeakers with different channels for appropriately distributing, e.g., the “right” and “left” channels of stereophonic sound. Because the subjective improvement of musical sound from stereophonic music sources is mostly due to the incoherence among the channels, the spatially distributed loudspeakers need not be arranged in the right-left configuration of traditional stereo sound systems. The system can also be provided with one or more “woofer” loudspeakers, cross-over filters, and/or power amplifiers to raise the output level and/or improve the quality of the musical sound. 
         [0040]    In addition, it was described above that the system controller can receive voice signals and a sound masking signal, and provide the voice signals and the sound masking signal to a plurality of spatially distributed loudspeakers over multiple channels. In alternative embodiments, the system controller can be configured to incorporate any suitable digital signal processing capability to allow a user to select any desired functionality or any desired combination of functionalities, including but not limited to voice lift, sound masking, paging, pod-casting, emergency broadcasting, and/or remote learning. 
         [0041]    It will be appreciated by those of ordinary skill in the art that modifications to and variations of the above-described distributed emitter voice lift system may be made without departing from the inventive concepts disclosed herein. Accordingly, the invention should not be viewed as limited except as by the scope and spirit of the appended claims.