Abstract:
Disclosed herein are teleconferencing pods that include a microphone and a loudspeaker for open-air conversations, connectible to a separate telephonic device that generates an intermittent sidetone that is active at certain times not in the control or monitoring of the pod. In those pods is a sidetone suppressor that suppresses a distracting open-air echo produced from the intermittent sidetone and a compensator that detects sidetone transitions to avoid generating an echo signal in the pod and to avoid adapting suppression in the absence of an externally-generated sidetone. Sidetone suppression may be by several means, and may include variables controlled by adaption, including delay factors, scalers and coefficients. Detailed information on various example embodiments of the inventions are provided in the Detailed Description below, and the inventions are defined by the appended claims.

Description:
BACKGROUND 
     The claimed systems and methods relate generally to loudspeaker teleconferencing systems that utilize full duplex operation with distant participants, and more particularly to teleconferencing pods that can connect to a telephone device generating an intermittent sidetone that is active at certain times not in the control or monitoring of the pod, wherein the pod includes a sidetone suppressor and compensation function to avoid applying suppression in the absence of an externally-generated sidetone. 
     The inventions described herein relate to conferencing systems that can connect to a telephonic device in systems such as that depicted in  FIG. 1 . In that system  100 , a telephonic connection is made between a local participant in proximity to a conferencing pod  102  and a distant party  108  using distant party equipment and/or devices, not shown. In system  100 , a telephonic device  104  is used to make a connection  107  with distant party  108 . Herein the term telephonic and telephone refer not only to devices and systems that utilize a public switched telephone network (PSTN), but also other devices that can make an audio connection between a local participant and a distant participant through any kind of network or connection including point-to-point, wired, wireless, switched packet and any other. The telephonic device  104  includes a keypad and/or controls  106  for controlling the connection  107  to distant party  108  and optionally other controls such as volume, mute and others. Conferencing pod  102  may connect to device  104  by simulating another device type such as a headset. Hereinafter the term “connector” includes not only physical connections, but also terminals and contacts of any type, and also digital, network, wireless or virtual connections. 
     Telephonic device  104  may produce a sidetone. The term sidetone has several historical meanings, and originates from the early days of radio when Morse code was used. To provide feedback to the radio equipment operator and audible tone was produced in a headset worn by the operator at times when the transmit key was depressed. In devices using an audio signal the term sidetone has come to mean a retransmission of an audio signal received at a local microphone to a local participant, for example through a headset. This is done as feedback to the local participant that his words are being transmitted. Sidetone generation and use can be understood in reference to  FIG. 2A , wherein a simple telephonic device is illustrated. The device of  FIG. 2A  is a stand-alone telephonic device, with an incoming port  208  and an outgoing port  206  for carrying audio to and from a distant participant. This device also includes a speaker  202  and a microphone  200 . Speaker  202  and microphone  200  would ordinarily be made part of a headset or other equipment whereby speaker  202  is positioned near the ear of local participant  204 , and the sound of  213  produced by speaker  202  is not substantially carried to microphone  200 . 
     Where sound produced by the Speaker  202  is not being carried to microphone  200  it may be desirable to include a sidetone generator  210 . The sidetone generator produces an audio signal received at the microphone  200  at a low level, typically less than what listener  204  hears a distant participant, providing feedback to the listener  204  that his speech is being transmitted to the distant parties. That audio signal is fed to a mixer  212  along with the distant audio received at port  208  producing a signal at speaker  202  that includes both the distant audio and a sidetone. 
     Now referring to  FIG. 2B , the functional aspects of a system as shown in  FIG. 1  are illustrated. The system of  FIG. 2B  includes a telephone device having many of the same components as that of the stand-alone device, including an incoming port  208 , an outgoing port  206 , a sidetone generator  210  and the mixer  212 . Although this telephone device might include a speaker and microphone, here a connection is made to a separate device through an incoming connector  216  and an outgoing connector  214  which supplies an incoming and outgoing audio signal to an external device, for example a headset. The external device connects to connectors  214  and  216 , and includes its own speaker  203  and microphone  201 . If the external device is a conferencing pod, speaker  203  will be configured to produce sound in the local vicinity so that the local participants  204  can hear the distant audio received at port  208 . Microphone  201  is likewise configured to pick up sound in the local vicinity of the pond such that the local participants can be heard by the distant parties. 
     The presence of sidetone generator  210  introduces a problem. The inclusion of sidetone generator  210  in the telephonic equipment may be on an assumption that external equipment connected to ports  214  and  216  is a headset, or rather that a substantial transmission path does not exist between the speaker and microphone at the external device. However, the presence of a conferencing pod does indeed introduce such a path  222 . Thus, distant audio produced at Speaker  203  is carried to microphone  201  and transmitted over path  222  through the outgoing connector  260  distant participants. This is perceived by the distant participants as an echo with the delay approximately two times the propagation delay between the local and the distant participants. Additionally, because of the presence of a sidetone generator  210  a feedback loop is introduced in the local equipment. This is experienced by the local participants and the distant participants as ringing and, if the coupling between speaker  203  and microphone  201  is sufficient, howling. 
     Therefore, the situation presented in  FIG. 2B  illustrates a particular problem where a conferencing pod is to be connected to a telephone in substitution of a headset, although that is not the only situation that the inventions which are described herein may be applied to. However, the situation provides a convenient illustration to describe the configuration and operations described in the discussion below. 
     BRIEF SUMMARY 
     Disclosed herein are teleconferencing pods that include a microphone and a loudspeaker for open-air conversations, connectible to a separate telephonic device that generates an intermittent sidetone that is active at certain times not in the control or monitoring of the pod. In those pods is a sidetone suppressor that suppresses a distracting open-air echo produced from the intermittent sidetone and a compensator that detects sidetone transitions to avoid generating an echo signal in the pod and to avoid adapting suppression in the absence of an externally-generated sidetone. Sidetone suppression may be by several means, and may include variables controlled by adaption, including delay factors, scalers and coefficients. Detailed information on various example embodiments of the inventions are provided in the Detailed Description below, and the inventions are defined by the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the conceptual elements of a conferencing system utilizing a conferencing pod that connects to a generic piece of telephonic equipment. 
         FIG. 2A  illustrates the concept of a sidetone in telephony. 
         FIG. 2B  illustrates the traversal of a sidetone through a conferencing system utilizing a conferencing pod. 
         FIG. 2C  illustrates the interaction of a sidetone suppressor in a conferencing system utilizing a conferencing pod connected to a telephonic device including a constant-sidetone generator. 
         FIG. 2D  illustrates an error condition in the system of  FIG. 2C  after removal of an external sidetone generator. 
         FIG. 3  conceptually illustrates certain elements of a conferencing pod system that includes an acoustic echo canceller, a sidetone generator and a sidetone suppressor. 
         FIG. 4A  depicts a first exemplary conferencing pod having a breakout box for connecting to an external telephonic device. 
         FIG. 4B  depicts the conferencing pod of  FIG. 4A  wherein the breakout box is configured to connect to a headset connection of an external telephonic device. 
         FIG. 4C  depicts the conferencing pod of  FIG. 4A  wherein the breakout box is configured to connect to a computer. 
         FIG. 4D  depicts the conferencing pod of  FIG. 4A  wherein the breakout box is configured to connect to a videoconferencing telephonic device. 
         FIG. 5A  depicts a second exemplary portable teleconferencing pod in relation to a U.S. quarter. 
         FIG. 5B  shows external parts of the product of  FIG. 5A . 
         FIG. 5C  depicts the conferencing pod of  FIG. 5A  configured to connect to a computer. 
         FIG. 5D  depicts the conferencing pod of  FIG. 5A  configured to connect to a headset connection of an external telephonic device. 
         FIG. 5E  depicts the conferencing pod of  FIG. 5A  configured to connect to a cellular telephone. 
         FIG. 5F  depicts the conferencing pod of  FIG. 5A  configured to connect to a source of audio playback. 
         FIG. 5G  depicts the conferencing pod of  FIG. 5A  configured to connect to a videoconferencing telephonic device. 
         FIG. 6  conceptually illustrates the elements of echo cancellation in a conferencing device. 
         FIG. 7  depicts a screen of exemplary teleconferencing product software allowing configuration for connection to various audio devices. 
         FIG. 8A  shows the interaction of elements of a simplified sidetone suppression system. 
         FIG. 8B  shows the interaction of elements of a sidetone suppression system that applies a coefficient profile to generate a suppression signal. 
         FIG. 9A  illustrates the elements of an exemplary sidetone suppression and compensation system in an initial state in the presence of an externally-generated sidetone. 
         FIG. 9B  illustrates the condition of the system of  FIG. 9A  after suppressor adaption to the sidetone. 
         FIG. 9C  illustrates the condition of the system of  FIG. 9A  after suppressor adaption followed by removal of the external sidetone and remedial action. 
         FIG. 9D  illustrates the condition of the system of  FIG. 9A  after suppressor adaption following an interruption and return of an external sidetone. 
         FIG. 9E  illustrates the condition of the system of  FIG. 9A  after suppressor adaption under the condition of far-side singletalk. 
     
    
    
     Reference will now be made in detail to particular implementations of the various inventions described herein in their various aspects, examples of which are illustrated in the accompanying drawings and in the detailed description below. 
     DETAILED DESCRIPTION 
     Described herein are certain teleconferencing products for communicating between a local and one or more distant or far-end participants. Those products will typically include an enclosure, one or more microphones for picking up local sound or speech and one or more speakers for generating audio from an audio signal received from the one or more distant conferees. The speakers will be driven by or may be included in a sound producing circuit, for example a power amplifier, and the microphones by a microphone circuit, for example a preamplifier. These devices will include a full-duplex port, which is a transmitter and receiver channel in one bundle, however a full-duplex port can be fashioned from a separate transmitter and receiver channels. The teleconferencing products may or may not utilize frequency decomposition, which is the application of audio data processing in sub-bands. These products need not utilize frequency decomposition, but may rather process wide-band audio data if desired. 
     It is to be understood that certain substitutions and modifications may be made to the products described herein without departing from the disclosed and/or claimed inventions. For example, in today&#39;s signal processing equipment an audio signal may be represented as a stream of audio data, and these are synonymous herein to their respective analog and digital domains. Likewise, where an implementation is described as hardware, it can just as easily be made with software, and vice versa. Exemplary products are presented with certain features, which may contain particular implementations of the inventions described and claimed herein. Where a claimed invention is described with reference to any particular implementation, it is to be understood that this is merely for convenience of description and the inventions so described are not limited to the implementations contained herein. 
     Some conferencing products may include more than one communication port for communicating participants in more than one location. Others of the products may be connected to an audio signal source at the same time as a connection with a distant participant. A conferencing system utilizing echo cancellation may feed the audio between two distant participants to each other, otherwise they might not hear each other. Certain of conferencing products might be configured or switched such that the audio from one participant is not transmitted to another, thereby permitting a partial private audio line from a distant participant to the local participants. By replacing a connection to a conferee with a connection to an audio source, which could be any source of audio including a playback device or a broadcast receiver, a local participant may listen to that audio source while not transmitting that audio to distant participants. The configuration may be by a physical, logical or a software switch, which can be implemented as a checkbox or other graphical control element. This effect may be one way, meaning that one party is private, or multi-way if it is desired to keep the speech of more than one party private from the others. The effect may be controllable, even during a conference, if it is desired to have a partially private conference for part of the time. 
     Now continuing the discussion above and referring to  FIG. 2C , a conferencing pod may provide suppression for the sidetone  221  produced by generator  210 . This may be accomplished by a sidetone suppressor  218  and a mixer  220 . Sidetone suppressor  218  predicts the sidetone that will be generated by generator  210  and produced at Speaker  203 . The inverse  223  of this predicted sidetone signal is injected to mixer  220 , thereby reducing the sidetone produced at speaker  203  to a level that is not perceptible, or at least is not distracting and/or a nuisance. Sidetone suppressor  218  may receive the signal of microphone  201 , or might be input with a different signal that includes the signal received at microphone  201 , for example where several microphones are present. Sidetone suppressor  218  may include coefficients, for example through an adaptive filter, that characterize and profile the sidetone generated by generator  210  as compared to the signal received at microphone  201 . Alternatively, another method of predicting a generated sidetone may be used. 
     A system described by  FIG. 2C  will work to suppress a sidetone at speaker  203  so long as the configuration remains stable. However, it may be that a sidetone generator  210  is not always present. For example, a piece of telephonic equipment may disable the generation of a sidetone at times when the local participant audio is not being transmitted to a distant participant. This may occur for example if the telephonic equipment includes a mute button, or also might occur at a time when a connection is not present to a distant participant or even when the telephonic equipment is powered off. 
     Such an event produces the state depicted in  FIG. 2D , were effectively a sidetone generator  210  is not present. In that state a sidetone  221  does not arrive at mixer  220 , and suppression signal  223  arrives at speaker  203 . Because the suppression signal is similar to the sidetone in the inverse, a local participant will hear an effective sidetone even without generator  210 . Sidetone suppressor may be adaptive, in which case this pseudo-sidetone will be evident until adaption occurs. Additionally, if the sidetone suppressor is adaptive, it adapts to the absent sidetone generator, and thus if that generator is later reintroduced sidetone will be heard, which may lead to ringing, feedback or other disturbances. 
     In the ideal case a telephonic device would recognize the device which is connected to it, enabling a sidetone generator when a headset is attached and disabling the generator when a conferencing pod is attached. In the alternative, a conferencing pod could receive a signal from the intermittent sidetone-generating device and the pod could apply sidetone suppression at appropriate times. However, in today&#39;s devices no such signals are known; rather the designs of many telephones simply require that a headset and not a conferencing pod be connected. Described herein is a method of detecting a sidetone transition from on to off and, by way of sidetone amplitude detection, from off to on, thereby providing a virtual missing signal of sidetone generation presence to a pod allowing for appropriate sidetone suppression. 
     Exemplary Conferencing Pods 
     Two exemplary conferencing pods are now described which may implement intermittent sidetone detection, which take the general architecture shown in  FIG. 3 . In that architecture and functionality of a conferencing device is divided between a conferencing pod  302  and a telephonic device  304  which in this case is a standard telephone. Telephone  304  may include a sidetone generator  334  in some configurations, although that is not necessary. Sidetone generator  334  may provide for intermittent operation. A telephonic device  304  includes an outgoing ports  336  and an incoming port  338 , which in this example are included in a single RJ-11 connector standard to public telephone systems. A telephonic device  304  may include means for transmitting sound to a local participant using a speaker or earpiece, and may also include a microphone. A telephonic device  304  further includes a local audio input port  330  in a distant audio output port  332  for a connection with an external set device that includes a speaker and a microphone. Ports  330  and  332  may be embodied as separate connectors were in a single connector, such as a 3.5 mm (⅛ inch) mini plug commonly used for headsets that connect to ordinary telephones. As will be seen below, any kind of connector may be used to provide port  330  and  332 , and no particular one is required. 
     A conferencing pod  302  is provided having a microphone  310  in the speaker  312  transmitting sound to local participants in local vicinity of the conferencing pod. The connection is made to telephonic device  304  by way of an outgoing port  322  and an incoming port  324 . In the exemplary conferencing pod  302  and acoustic echo canceler  314  is provided, although it is not required. Acoustic echo canceler  314  applies and echo cancellation signal to the outgoing audio stream by way of mixer  316 . Conferencing pod  302  also includes a sidetone suppressor  318  injecting a suppression signal into mixer  320 . In this example the sidetone suppressor receives as input signal being delivered to the telephonic device  304  through the output port  322  after any processing performed on the signal received a microphone  310 , although a different system might be constructed using an input located elsewhere. 
     Conferencing pod  302  may include other features and components in many different configurations. For example, microphone  310  may be substituted with a microphone array in a configuration to provide omnidirectivity or noise cancellation. Speaker  312  could be substituted with an array as well. Conferencing pod  302  might be fashioned in any form factors and with controls, displays and other user interactive features. Microphone  310  and speaker  312  could also be substituted for a headset worn on the head or a handset held in the hand. 
     A first exemplary conferencing pod  400  is shown in  FIG. 4A  in a first configuration together with a telephone breakout box  402 . Located to the pod are a central speaker  404  and three microphones  406   a ,  406   b  and  406   c . Also in this example are lighted indicators on the microphones that indicate when the pod is un-muted. Volume up/down controls  408  are provided to control the volume of sound produced that speaker  404 . Indicator lights  412  show the volume state as controlled by controls  408 . A mute button  410  toggles the mute function of the pod. 
     A telephone breakout box  402  connects to pod  400  through a cable  414 . Telephone breakout box  402  toggles between pod  400  and a headset connected to box  402 , as will shortly be discussed. A headset toggle button  412  performs this toggling function. Now referring to  FIG. 4B , it can be seen that telephone breakout box  402  includes several socket connectors at the rear, which are as follows. A connector is provided for data cable  414 , again connecting pod  400  to box  402 . Another connector is adapted to receive a telephone cable  416  which connects to a telephone device  420  in its headset jack, in this example through an RJ-9 connector although in other examples with other connector types. Another connector is provided for a headset cable  418  leading to a headset  422 , which may use the same or a different connector type as cable  416 . A power connector receives power from a power supply  424 , which in this configuration also supplies power through cable  414  to pod  400 . 
     Using this first configuration, pod  400  may connect to an ordinary telephone  420  with a headset connection, thereby adapting telephone  420  into a conference phone. By pressing headset toggle button  412  a user can switch between conference mode and headset mode, thus preserving the headset function of the telephone  420 . The reader will recognize that the concepts presented so far are applicable to this configuration. 
     In a second configuration shown in  FIG. 4C , pod  400  is connectable to a computer  430  through a USB cable  414 . In this way, pod  400  may be made operable with a softphone on computer  430  by making speaker  404  an output audio device of the computer and microphones  406   a ,  406   b  and  406   c  as input audio devices to the program. Pod  400  receives its power through cable  414 , which is configured to connect to a USB port of the computer  430 . Note that in this example cable  414  is also used in the telephone configuration, although there power is not supplied from a computer but from an external power source. 
     Now turning to  FIG. 4D , a third configuration is shown for using pot  400  as part of a videoconferencing device. For this application a videoconferencing breakout box  440  is provided which connects to pot  400  using the same cable  414  and utilizing an external power source, not shown. In this example videoconferencing device  442  provides a video camera and connectors providing audio out  444  and receiving audio in  446 . Included in videoconferencing breakout box  440  are an audio output connector  448  and an audio input connector  450 . A cable  452  is provided that interconnects audio inputs,  450  and  446 , and outputs,  448  and  444 , so as to deliver local audio picked up by microphones  406   a ,  406   b  and  406   c  to videoconferencing device  442  and distant audio from videoconferencing device  442  to pod  400  and speaker  404 . Also included in cable  452  are connectors for connecting to audio input connectors  454  included in monitor  456  should it be desired to use speakers included in the monitor rather than in the pod. 
     Thus it may be seen from the first exemplary product that a conferencing pod may connect both to a telephonic device and a non-telephonic device. For some non-telephonic devices it may be that a sidetone is not generated, and thus providing sidetone suppression is not appropriate. However, if a sidetone suppressor is adaptive to the conditions experienced it may be that a sidetone suppressor may remain enabled with adequate performance even though a sidetone generator is not present. An optional feature present in conferencing pod  400  is a setting that enables and disables the sidetone suppressor, which feature is settable in the configuration of  FIG. 4C  through software. Other methods of enabling and disabling a sidetone suppressor may be used as desired. 
     The exemplary product of  FIGS. 4A ,  4 B,  4 C and  4 D may be used with analog telephones, digital telephones, packet-switched telephones, videoconferencing systems, network telephones, softphones, voice over IP telephones and software applications, Internet conferencing applications and others in interactive conversational mode with a distant participant. This product may also be used as an attachable microphone and/or speaker to a computer or other device, for example to create an audio recording and/or playback device. Other products described herein can likewise be used. Additionally, other breakout boxes might be designed to accommodate other communications devices, and the inventions described herein are not limited to the particular exemplary products so described. 
     A second exemplary product, to which the inventions described herein may be applied, is intended as a portable and versatile speakerphone product  500 , and is relatively small as can be seen in  FIG. 5A  in comparison to a U.S. quarter. Referring now to  FIG. 5B , that product includes a housing  502 , an audio speaker  503 , a microphone  504 , and operational indicator light  505  and control buttons  506  permitting the control of speaker volume and mute on/off. Note however, this example does not include a breakout box for separating connectors as in the first exemplary product, rather connections are restricted to those provided in the product  500  itself. 
     One difference between product  500  and other products through which a teleconference might be attempted is that this product is designed to be personally adaptable. Most teleconferencing products are designed with a particular channel in mind, for example an ordinary telephone line or its recent substitute, Voice Over Internet Protocol (VOIP). Thus, an ordinary teleconferencing product will include a port to interface with a single channel. This product provides an interface to several channel types, by which a user can make a connection to one of several or more channels that happen to be available at the moment. 
     Referring now to  FIG. 5C , product  500  is connectable to a computer, for example laptop  513 , by way of a Universal Serial Bus (USB) connection. That connection is made by way of cable  511  connecting a first port  510  in product  500  and a port  512  in the computer  513 . In this connection configuration, product draws its power through the USB cord  511 , and no external power supply is needed unless the port  512  is not a powered USB port (supplying 500 mA at 5V or 2.5 W) Computer  513  includes software, which may include a driver, that provides for digital communication between product  500  and the audio system of the computer  513 , through which audio information input at microphone  504  is made available to computer  513  and audio output information as provided by computer  513  and software running thereon is produced at speaker  503 . For example, computer  513  may have an audio subsystem made available to applications generally. Driver software may provide an item in a pull-down menu list of input and output audio selections, and thereby a user can select microphone  504  as input and/or the speaker  503  as output for applications running on the computer generally. 
     Alternatively, application software may provide for specific input or output through the product  500 . For example, a VOIP soft phone may utilize the product&#39;s speaker and microphone, while other applications utilize the general settings for the computer&#39;s speakers and microphone, if those are connected. As will be seen, configuring the audio between general audio channels from the speaker phone channels makes possible certain effects. 
     Continuing to  FIG. 5D , the product  500  is connectable to a telephone  518  in place of a handset or headset jack  519  by way of cable  515   a  insertable to port  514  in the product  500 . In this configuration, an external power supply  517  is provided for socket  516 , although other power sources could also be designed into a portable conferencing device such as batteries. In this configuration the product  500  emulates a headset device, receiving and producing analog signals at voltages, currents and impedances suitable for telephone  518 . 
     Now referring to  FIG. 5E , the product  500  may also function as a speakerphone utilizing a wireless telephone  519 , which might be a cellular or a cordless telephone. The product  500  is connectible with not only telephones, but with other media devices, as will become clear below. A different cable  515   b  is used to make the connection between the product  500  and the telephone  519 . Cable  515   b  includes and presents three conductors through its jack connectors: an input, an output and a ground. Cable  515   a , intended to emulate a handset, includes four connectors at the telephone side, but three connectors at port  514  by tying a speaker and a microphone line together, for example at the negative (ground) polarity. 
     Cables  515   a  or  515   b  could include one or more resistive elements for impedance matching between the speakerphone device and the telephone. If that is done, a cable will become compatible with a set of media devices, but may not function properly in others. For example, it may be desirable to connect a speakerphone device to a music player  520  as in  FIG. 5F  or to desktop video conferencing device as in  FIG. 5G . A cellular phone  519  or an audio player  520  may be configured to be connected to a small speaker, which presents a relatively low impedance as compared to an audio source at “line” levels. Likewise, a media device might accept an input directly from a microphone, such as is done for most telephones, while other media devices might accept an amplified audio source such as the video conferencing device  521 . 
     To achieve improved compatibility with media devices of various kinds, the product  500  is designed to vary its driving and/or gain characteristics on port  514 , whereby a single cable  515   b  may be used for devices having that particular end connector, which in this example is a stereo 2.5 mm male connector. Those port characteristics are programmable through a microcontroller embedded within the product  500 . That product is designed to be configured through a USB connection made through port  510 . That configuration includes the adjustment of the input and output audio voltage/gain levels, enabling/disabling the mixing of the USB and analog port audio, enabling/disabling line echo cancellation, and disabling the product&#39;s speaker  503 , some of which features will be further described below. In the product  500  the input and output audio lines are current-limited with in-line resistors, therefore modification of the audio gain levels has the effect of matching the input receiver of a selected media device. In comparable devices, matching may be through gain-adjustable amplifier circuits, current sources or sinks, or any other method. Gain matching may also be adaptable, through the use of an automatic gain control, if desired. An output bandwidth of approximately 150 to 15,000 Hz and an input bandwidth of about 50 to 8,000 Hz provides a good range for playing music and for picking up speech. 
     The host software of products  400  and  500  include a database of settings suitable for a number of media devices. Selection is made in a screen as shown in  FIG. 7 . The user is directed to select first a media device type, which in this screen includes the cell phone, instant messaging, internet telephone, mp3 player, regular telephone, video conferencing, VOIP softphone and web conferencing types. Upon selection of a type, a user may select a manufacturer and a model corresponding to the media device intended to be connected to the product. On selection of a device, the user clicks on the “Apply” button to download the configuration suitable for the selected device to the product. A user is permitted to vary the settings for a media device or add a new device through the “advanced” menu, not shown. 
     Both of the exemplary products include echo cancellation, such as that described below, auto-leveling of microphone inputs, noise cancellation and full-duplex operation. It is to be understood that the echo cancelling systems and concepts described below are optional and exemplary, and stand separate from the inventions described and claimed herein. 
     Echo Cancellation 
     Again, products disclosed above include an echo canceller, which allow for increased audio quality in full-duplex operation by preventing certain echos from reaching a distant party. Some echo cancellers may utilize a finite-impulse response (FIR) filter and others might use an infinite-impulse response (IIR) filter, which filters include a number of coefficients representing the sum of the echo paths in the environment of the product in operation. The echo canceller may produce an echo cancellation signal, which is a continuous signal that is either added to or subtracted from the signal received at the one or more microphones. 
     For those products implementing an FIR or IIR echo canceller, the coefficients are adapted or converged over a period of time where there is incoming audio from a distant participant but silence in the product&#39;s local vicinity. The adaptation of coefficients may be through a converger or adapter that applies an iterative method to arrive at an echo cancelation solution. Coefficient adaptation may be controlled such that those coefficients are adapted generally where there is a substantial far-end audio signal and no detected sound produced in the local environment. 
     A doubletalk detector may be included to discriminate between a condition of far-end audio only, called far-end singletalk, and a condition of audio on the near and a far-end of the conversation which is called doubletalk. The doubletalk detector may track the conversation between conferees to identify appropriate times to engage coefficient adaptation. 
     In certain portable products, a speaker and microphone will be present in the same enclosure, and audio will be coupled directly between a speaker and a microphone. Those portable products may be quite small, sometimes small enough to place in a briefcase, purse or pocket. 
       FIG. 6  serves as an introduction to the concepts of echo cancellation, depicting the elements of one side of a conferencing system. A conferencing device  600  is connected to a far-side participant through a carrier medium  612 , which might be a telephonic channel, for example. Near-side audio is received at microphone  604  and delivered to the far side device at times through medium  612 . As far-side audio is received, device  600  produces audio at speaker  602 . The sound produced at speaker  602  is picked up by microphone  604  through a feedback path  614 . Thus, the far-side participant will hear an acoustic echo of himself with approximately two-times the carrier medium latency plus path latency  614 , if production of sound received from path  614  is not controlled or cancelled. 
     Device  600  may include an echo controller  616  for reducing acoustic echo. Standard methods of control include operation at half-duplex, and operation at full-duplex with echo cancellation. Half-duplex operation simply cuts off the sound received at microphone  604  when the audible volume at speaker  602  exceeds a pre-selected threshold. Many conferencing products implement half-duplex operation, however that operation carries a disadvantage that participants at only one side of the conference can be heard at any time, and neither side can interrupt or acknowledge the other. 
     When possible, it is therefore preferable to apply echo cancellation to achieve full-duplex operation. In digital audio systems, echo cancellation can be performed by subtracting off, at controller  616 , a modified version of the signal produced at speaker  602 , leaving only near-side audio. A conceptual method of cancellation merely applies an attenuation and a delay to the outgoing audio, accounting for the delay and attenuation of feedback path  614 . However, in the real world path  614  is complex, including dispersed components from reflections off the several surfaces and persons in proximity to the speaker and microphone. 
     To deal with that complexity, controller  616  ordinarily implements echo cancellation through use of a finite impulse response (FIR) filter, with the received far-side audio signal as input. The FIR filter utilizes a finite number of coefficients of a length sufficient to cover the longest path  614  of significance expected in operation. The reader should recognize that acoustic echoes will be, in general, of longer duration and greater complexity than line echoes. An acoustic echo canceller therefore requires a much larger number of coefficients to provide echo cancellation, which might cover a number of seconds in a device designed for operation in high-echo rooms (rooms with parallel walls and no carpeting.) These coefficients are applied to a copy of the incoming audio, providing the predicted echo component received at the microphone. The determination of these coefficients is by an iterative method, generally understood by those skilled in the art, and will not be further described here for the sake of brevity. In theory, the FIR coefficients could be determined by the application of a step function to the speaker and a recording of the received audio (in reverse) received at the microphone. 
     In practice, however, the convergence of the FIR coefficients depends mainly on the presence of an incoming audio signal and the general absence of near-side sound apart from that produced by the device&#39;s speaker. This may be performed by measuring the incoming (distant) audio level, the microphone audio level received at the microphone(s), and the audio level following the echo canceller. An indication of good FIR coefficient adaptation is a high volume detected before echo cancellation and a low volume afterward, which can generally only occur if there is significant coupled far-side audio in the absence of near-side audio. 
     To avoid non-convergence or divergence of the FIR coefficients, the convergence operation should be enabled while there is an incoming far-side signal, with near-side audio at a volume about less than the desired degree of echo cancellation. Operation in the presence of a near-side signal may introduce random errors into the coefficients, while operation with a weak far-side signal can result in a non-converging filter. The second general condition of operation is that convergence should not proceed while there is a substantial near-side signal. Thus, if the FIR coefficients are well-adapted, the system can detect this condition again by periods of high amplitude at the microphone and low amplitude in the echo-cancelled signal. If badly adapted, such a condition will generally not occur, and the levels before and after the echo canceller may track each other or even have a higher after-echo canceller amplitude, in which case the echo canceller is producing echo. Regardless of the state of the echo canceller, the system can detect the presence of near-side audio in the absence of far-side audio, because a high-amplitude signal will be received at the microphone and a low-amplitude signal will be received from the distant conference device. A doubletalk detector may also be used to discriminate other cases where both sides of a conversation may be speaking. 
     Sidetone Suppressors 
     The inventions described herein are operable with a sidetone suppressor, which is a component that reduces the volume of a generated sidetone as perceived by a person. Two exemplary sidetone suppressors are shown in  FIGS. 8A and 8B , representing two of a large number of suppressor types that may be used; which examples are presented here mainly to introduce concepts that will be understood by one of ordinary skill in the art. Both examples include an input port  700  or receiving an audio signal that potentially includes a sidetone. Also in both is a microphone input  702  and a speaker output  704 . An input buffer  712  buffers a number of samples from the microphone  702 , with a length sufficient to store the number of samples that will occur through one sidetone loop, which loop is the feedback path between the microphone  702  and the appearance for its duration of a sidetone on input  700 . 
     In the first exemplary suppressor of  FIG. 8A  a controller  710   a  reads certain inputs and produces certain outputs. A meter  706  measures the volume level in the audio signal received at port  700 , and another meter  708  measures the volume level in the sidetone-suppressed signal produced at speaker  704 . Thus, the pre-SS and post-SS meters provide information whereby it may be determined whether effective suppression is occurring, because a low volume level will be seen following the suppressor or higher volume level is received at input  700 . Controller  710   a  reads  720  the pre-SS meter  706  and also reads  721  the post-SS meter  708  to, among other things, determined whether effective suppression is occurring. 
     In this example sidetone suppression is accomplished by an offset buffer of one sample  714 , a scaler  715  in the summer  717 . Controller  710   a  controls  722  the offset  713  into buffer  712 , thereby presenting an audio sample from input port  700  to scaler  715  at a delay corresponding to the sidetone loop, i.e. the time it takes for a sound received at microphone  702  to appear input  700 . Controller  710   a  takes measures to match the offset  713  with the actual sidetone loop in operation. Controller  710   a  also controlled scaler  715  to match the attenuation that is provided by the sidetone generator, for which meters  706  and  708  are used. 
     The example of  FIG. 8A  represents a very simple sidetone suppressor, suitable in situations where a sidetone generator produces a sidetone that is an identical or close replica of a microphone signal, after scaling and a delay. It could be the case, for example, where the system from the microphone  700  to the input  702  is entirely digital. However, it is foreseeable that a portion of the sidetone will include analog components such as wires carrying an analog signal with an associated capacitance, resistance and inductance, and also filters and other circuits that distort and spread the signal. Some compensation can be rendered by the application of a smoothing filter to the samples placed in buffer  712 , which may be sufficient for some applications. 
     A more robust sidetone suppressor can be constructed, as shown in  FIG. 8B . This exemplary suppressor includes the same input port  700 , microphone  702 , speaker  704 , meters  706  and  708 , and buffer  712 . However, in this example an array of coefficients  716   a  is provided that performs the functions of buffer  714  and scaler  715  in the prior example. Each coefficient is applied to a buffer  716   b , which buffer is reloaded from the master buffer  712  and coefficients applied for each sample received at microphone  702 . Each coefficient of array  716   a  represents a scaling factor at its particular offset, and thus the suppressor of  FIG. 8B  is capable of suppressing sidetones that are distorted and/or more complex. Each coefficient is multiplied with its corresponding sample in buffer  716   b , which products are summed to form one sample in a suppression stream applied at summer  717 . 
     Controller  710   b  adapts  726  the coefficients of array  716   a  to match the sidetone received at port  700 . This may be through an iterative method that converges on a solution in a particular time, which time may be selected to be sufficiently short at initialization to rapidly suppress sidetones but long enough to avoid coefficient divergence on spurious events. The inputs to that iterative method may be the samples  725  received at microphone  702 , the samples  727  following application of the coefficient array  716  and the resulting sample stream  728  after application of summer  717 . Meters  706  and  708  may still be used to measure the effective suppression. 
     Recognize now that the examples of  FIGS. 8A and 8B  are adaptive; controllers  710   a  and  710   b  adapt the sidetone suppression to the sidetone existent at port  700 . In a fixed system, with an understood sidetone having a known attenuation and delay, adaption may not be needed. However, referring back to  FIG. 3 , where a conferencing pod  302  is to be connected to a telephone  304  with unknown sidetone generation, adaption is appropriate. Adaption is best performed under conditions where only local participants are speaking and distant ones are silent, so controllers such as  710   a  and  710   b  converge and/or adapt to signals related to the sidetone. The condition of having local audio in the absence of distant audio is referred to as near-end singletalk, as opposed to the conditions of far-end singletalk or doubletalk. It is to be recognized, however, that some noise will always be present in the system and adaption should not be prevented where a modest amount of distant noise occurs, particularly where a microphone signal is significantly above a measured or expected noise floor. 
     Sidetone Transition Detection and Countermeasures 
     As suggested above, a conferencing product can be adapted to interface with ordinary telephonic equipment, for example functioning as a headset or handset. (Herein, a “set” refers to one or more microphones combined with an earpiece that delivers sound at a relatively low power to a person&#39;s ear.) For example, the second exemplary conferencing pod is attachable to a telephone at the headset jack  519 , as shown in  FIG. 5D . Other equipment to which a portable teleconferencing device could be attached includes a cellular telephone, an intercom, a soft phone and many other multi-party devices. 
     A portable conferencing device might be connected to equipment that does not have a sidetone generator with consistent characteristics. For example, a portable conferencing device might be attached to a telephone having more than one line, each line having a separate sidetone generator. Alternatively, a portable conferencing device might be attached to a telephone in a PBX network having many lines and many potential sidetone configurations. In those configurations a user might switch from one line to another and thereby switch between two sidetone generators with different characteristics. Even if a portable conferencing device is not used in equipment having only one line, a sidetone generator may be intermittently present in the case where a telephone has a hold or privacy feature where local sounds are not reproduced. In such equipment, the interruption of sidetone might also be accomplished by disabling the audio output amplifier, or by sending a flat audio signal or a signal other than one containing a sidetone. Under conditions of such a sidetone interruption, an echo canceller can lose adaption to the sidetone, for example where the echo canceller is programmed to decay back to a default state. 
     Referring again to  2 C, consider the following example where a portable conferencing device is connected to telephonic equipment having more than one line and a hold feature. A local participant makes a connection with a distant party and holds a conversation for several minutes, during which sidetone suppressor  218  adapts to the characteristics of the sidetone generator  210 . The local participant then decides that he needs to have a private conversation with someone in his office, and places the call on hold. 
     The local participant now makes a connection with the person in his office, but here there is no sidetone generator present in the system, resulting in the situation shown in  FIG. 2D . When the far side office participant begins speaking, that signal  221  is carried and produced at the speaker  203  and picked up at microphone  201 . However, now the sidetone suppressor is still adapted for the presence of a sidetone generator, and signal  221  includes no sidetone. Suppressor  218  therefore overcompensates and actually produces a local sidetone at the same level as the sidetone generator would produce. The local participants then suffer the distracting and annoying effects thereby. 
     Thus it is now herein recognized that it may be that a sidetone generator is only intermittently present in a system, and might be effectively removed through participant action by a muting function on the telephone without indication to a sidetone suppression system. Again, there are two deleterious effects to continuing operation after withdrawal of a sidetone generator, which are generally effective generation of a false-sidetone by the suppression system and possible mal-adaption. These effects can be avoided if the sidetone suppression system can generate its own indications of sidetone transition events, i.e. the removal or introduction of a sidetone generator. By recognizing sidetone transition events, a conferencing pod may compensate by control logic for an intermittently-present sidetone generator, which control logic in combination with a sidetone suppressor is an intermittent sidetone compensator. 
     A method of detecting sidetone transitions will now be described, with reference to a system shown in  FIG. 9A . In that system, a local participant  910  may interact by speaking into a microphone  902  and listening to a speaker  908 . An input port  904  and an output port  906  connect to a telephonic device, not shown, receiving and sending an audio signal thereto. Thus, in this example, all the components shown between ports  904  and  906  and user interactive elements speaker  908  and microphone  902  are included in a conferencing pod. A sidetone suppressor  912  provides sidetone suppression for a signal received at input port  904 . Also in this example, a bypass switch  920  is provided whereby the output of speaker  908  can be selected to be the output of suppressor  912  or the unmodified signal received at input port  904 . 
     Further in the system of  FIG. 9A , meters  914 ,  916  and  918  are provided to give an indication to the system of audio levels experienced at various locations. A microphone meter  914  measures the volume of sound received at microphone  902 . A pre-sidetone suppressor meter  916  and a post-sidetone meter  918  measure the audio levels before and after the application of sidetone suppressor  912 . The system state shown in  FIG. 9A  is an initialization state, with a non-adapted sidetone suppressor  912 . In this state, a local participant  910  is producing local audio  950 , which is being returned in the form of a sidetone  952   s . Here, the sidetone  952   s  reaches switch  920  because the output of suppressor  912  is not effective. In this condition, a microphone meter  914  reads high and the pre- and post-meters  916  and  918  also read high, but at a lower volume than the microphone meter  914  because the sidetone  952   s  attenuated. In this condition to system may maintain switch  920  in a state that allows the output of sidetone suppressor  912  to reach speaker  908  so that adds suppressor  912  becomes adapted the best signal is presented to the local participant  910 . 
     Now turning to  FIG. 9B , as the suppressor reaches adaptation the pre-suppressor meter  916  will continue to read high in the presence of local participant audio  950 , but the post-suppressor meter  918  will read low. Thus, the sidetone  952   s  does not make it past the mixer of sidetone suppressor  912 . In this condition is appropriate for switch  920  to be in a position that allows the suppressed audio from  912  to be applied to speaker  908 . 
     The removal of the external sidetone generator leads to the condition shown in  FIG. 9C . There, the local participant is speaking and generating local audio  950 . But as there is no sidetone, the pre-suppression meter  916  reads low. As discussed before, in the circumstances sidetone suppressor  912  injects a suppression signal which results in a signal  954   s  appearing after the sidetone suppressor  912 , causing the post suppression meter  918  to read high. Signal  954   s  is referred to as an echo signal, as it is generally heard as an echo of the local participants speech. A low pre-suppression level in combination with a high post-suppression level is a null-sidetone indication. Detection of a null-sidetone may be prevented where meter  918  reads substantially less than or equal to meter  916 , for example by selecting a threshold ratio between these two meters that consistently filters out cases where a null-sidetone is not present. By these readings the system can determine that an indication that the sidetone generator has been removed, which is a sidetone transition event. The decision on whether a sidetone generator has been changed (either introduced or removed) by be made over a period of time; rather than applying an instantaneous test, information may be averaged over time and delays or hysteresis may be applied in accordance with the performance of a particular conference system. 
     On detecting a sidetone transition event the system may take remedial steps. These include bypassing the sidetone suppressor  912 , in this case by switching selection switch  920  to send the signal received at port  904  to speaker  908 . Another remedial step is to hold adaption of sidetone suppressor  912 , as the adaptive process is now deprived of an input. Thus, the state of suppressor  912  may be maintained in readiness in the event that the sidetone generator should be reconnected. Other steps may be taken on a sidetone transition detection (either on departure of a sidetone generator or a reintroduction), including the resetting of suppressor coefficients and/or increasing the rate of adaption of those coefficients. 
     Now turning to  FIG. 9D , a sidetone generator may return and produce a sidetone  952   s , again yielding a high meter reading before the suppressor and a low reading afterward. Being in a state of bypassing suppressor  912 , and recognizing that a local participant is speaking by high meter reading at the microphone  914 , the system can determine an indication that the sidetone generator has been replaced, which is also a sidetone transition event. Having this indication system ceases to bypass suppressor  912  by returning switch  920  to its normal, unbypassed position. 
     It may be recognized that a telephonic system should not be expected to generate a sidetone in the absence a local audio. Therefore, referring out to  FIG. 9E , microphone reader  914  reads low the system takes no action with regard to switch  920 , even though there may be some activity measured at meters  916  and  918  due to distant sound  956   d  (in this case meters  916  and  918  will be about equal). It is also to be recognized, however, that ambient noises in the vicinity of microphone  902  may create a noise floor and, is sufficient sound is available in the environment, the system may continue to identify sidetone transition events even though a local participant  910  is not speaking. Nevertheless, it may be desirable to set a threshold to be applied to meter  914  under which no sidetone transition events will be recognized This threshold may be set at a level that is below a normal speaking volume but above that of the range of noise floors expected in operation. 
     Also in the exemplary system, adaption of suppressor  912  is limited to those times when the echo return loss (ERL) is above a certain threshold, which is −18 dB in one exemplary device. In the example of  FIG. 9B , this can be seen by taking the ratio of pre-suppressor meter  916  over the value of microphone meter  914 . In this way, adaption of suppressor  912  can be avoided at times when only a weak signal is available. 
     Now although functions and methods implemented certain exemplary embodiments have been described above, one of ordinary skill in the art will recognize that these functions and methods may be generalized to like devices and are adaptable to other audio products, including but not limited to conferencing devices, hands-free devices, playback devices, and recording devices. Likewise, although the described functions have been described through the use of block diagrams and in hardware, one of ordinary skill in the art will recognize that most of the functions described herein may be implemented in software as well. Additionally, the exact configurations described herein need not be adhered to, but rather the diagrams and architectures described herein may be varied according to the skill of one of ordinary skill in the art. Furthermore, the echo cancellation filters described here utilize a finite impulse response filter, however other filters might be used, for example infinite impulse response filters.