Abstract:
An enhanced sidetone system is disclosed which provides the user of a telecommunications terminal, while speaking, with immediate audio feedback that corresponds to what the far-end party is probably hearing. The sidetone system continuously samples the input speech signal from the user and also obtains signal quality statistics of the transmission path. These statistics can include descriptions of network quality-of-service characteristics (e.g., packet loss rate, etc.) and/or media quality characteristics (e.g., audio distortion due to echo cancellation, etc.). These statistics enable the disclosed technique to determine whether the transmitted signal quality is acceptable. When an unacceptable condition in transmit-path signal quality is detected, the technique modifies the traditional (main) sidetone signal. For example, a delayed sidetone signal can be transmitted back to the user&#39;s terminal, in addition to the main sidetone signal generated, so that the user perceives the combination of sidetone signals as a hollow-sounding, objectionable sound.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to U.S. application Ser. No. 12/119984, filed May 13, 2008 (Attorney Docket: 630-338 us). 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to telecommunications in general, and, more particularly, to providing information in a sidetone signal provided to a user via a receive communication path, wherein the information serves as feedback about the signal quality in the corresponding transmit communication path. 
       BACKGROUND OF THE INVENTION 
       [0003]    Certain types of audio telephony are susceptible to degradations in voice quality. For example, cellular telecommunication is notorious for marginal-to-poor call quality at certain times of the day and year, and in certain geographic areas where coverage is a problem. As another example, Voice over Internet Protocol (VoIP) telecommunication has also been known to exhibit unacceptable call quality, depending on various characteristics such as how each phone gains access to the network, the audio encoding algorithms being employed, the traffic that is already present along the access paths, packet loss and delay, routing inefficiencies, and the traffic-handling capability of the network. 
         [0004]    A common problem is that the communication path between two call participants can be afflicted with poor call quality in one direction while the other direction still has acceptable quality. This occurs frequently in asymmetric networks that provide different upload and download speeds. A more annoying problem is that asymmetric voice quality impairments can be transient, especially with VoIP systems. A reason that voice quality asymmetry can occur with VoIP systems is that, unlike traditional telephone systems, VoIP networks tend to carry both voice and data. Illustratively, if a large amount of non-voice data are moved suddenly from Point-A to Point-B, while much smaller amounts are being moved from B to A, it would not be unusual during the data transfer for the voice quality from A to B to be worse than the quality from B to A. 
         [0005]    The annoying aspect of transient asymmetric voice quality impairments is that the speaker is often unaware of the impairment until informed of the problem by the other party. This is a situation that virtually every user of certain types of telecommunications networks (e.g., VoIP, cellular, etc.) has experienced at least once, often resulting in frustration and lost time because of the need to repeat what was said. Therefore, a need exists for an audio mechanism that will inform users, in real-time, that their voice is not being transmitted clearly to the other party or parties on the call. 
       SUMMARY OF THE INVENTION 
       [0006]    It is recognized in the present invention that when a telecommunications terminal user on a call hears degradation, the user tends to change the way that he or she speaks. Typically, the user speaks more slowly or more clearly, or she tries to confirm that the second party is able to hear adequately—for example, by sporadically asking, “Can you hear me?” or “Are you still there?” 
         [0007]    Meanwhile, it is also recognized that telephone systems have mechanisms that are intended to feed the user&#39;s voice back to the user&#39;s ear while the user is speaking. The traditional purpose of the sidetone signal is to provide feedback to the user about how loudly she is speaking, the sidetone being necessary because the telephone handset is covering one of her ears. It is well known that people tend to speak more loudly when using a telephone that has low sidetone and speak more softly when using a telephone that has loud sidetone. 
         [0008]    Prior to the advent of digital telephones and digital switching systems, the sidetone heard by users of wired analog telephones was created within the phone itself by a circuit commonly referred to as the “sidetone hybrid.” This circuit combines four wires within the phone (two for the microphone and two for the speaker) into a pair of wires that carries both the transmit and receive signals. The loudness of the sidetone varies as a function of the impedance mismatch between the telephone and its associated port on a private-branch exchange or switch. 
         [0009]    In modern digital and Voice over Internet Protocol (VoIP) telephones, sidetone generation is controlled by software or firmware. As was the case with wired analog telephony, the objective of the sidetone mechanism in these systems is to provide users with an accurate representation of their voice while they are speaking. In some environments, especially wireless telephony and VoIP, provision of distortion-free sidetone has represented a significant engineering challenge. An important point in this context is that deliberately distorting the sidetone signal would be straightforward, if one wanted to do so. The present invention takes advantage of this capability, in order to address the problem of a user being unaware of transmission impairments while he is speaking. Specifically, the present invention relies on an enhanced sidetone mechanism to provide the user of a telecommunications terminal, while speaking, with immediate audio feedback that corresponds to what the far-end party is probably hearing. 
         [0010]    The sidetone system of the illustrative embodiment, which is implemented at a private-branch exchange (PBX), continuously samples the input speech signal (i.e., the user&#39;s voice) and also obtains signal quality statistics of the transmission path that is in the direction from the user to the far-end party. Illustratively, these statistics might include descriptions of network quality-of-service characteristics (e.g., packet loss rate, latency, radio signal strength, radio interference, etc.) and/or media quality characteristics (e.g., audio distortion caused by poor echo cancellation, inaccurate transcoding between different digitization schemes, crosstalk, etc.) within specific time windows. The availability of these statistics enables the disclosed technique of the illustrative embodiment to determine whether the transmitted signal quality is acceptable or not. 
         [0011]    When an unacceptable condition in transmit-path signal quality is detected, the disclosed technique modifies the traditional (main) sidetone signal, possibly by introducing additional signal components. For example, in accordance with the illustrative embodiment, a delayed sidetone signal is transmitted back to the user&#39;s terminal, in addition to the main sidetone signal that is generated either at the phone or at the PBX. The amount of delay is engineered so that the user perceives the combination of the two sidetone signals (i.e., main and delayed) as a hollow-sounding, objectionable sound. Such a sound is of the sort often described by users as “what I would sound like with my head in a rain barrel”; it is created in accordance with the illustrative embodiment by delaying the second sidetone with respect to the main sidetone by between five and twenty milliseconds. In some embodiments of the present invention, the amplitude of the second sidetone signal is adjustable, as well as the amount of delay with respect to the main sidetone, thereby allowing the degree and nature of the distortion to be varied in response to varying conditions. 
         [0012]    In some embodiments of the present invention, a transient interruption of transmissions to the receiving party, of the sort of interruptions that occur frequently with wireless telephones, is indicated to the talking party by a corresponding, noticeable drop in sidetone amplitude. Other types of sidetone distortion that can be deliberately added include static, white or colored noise, clicks, pops, and hum. 
         [0013]    The different types of sidetone distortion that are created in response to different types of transmission impairments, and in accordance with the illustrative embodiment, advantageously serve to inform users about the types and severity of the impairments that are occurring. This information enables users to make immediate adjustments to their speech or physical location and to determine whether what they have said has been heard clearly by the other party. 
         [0014]    The illustrative embodiment of the present invention comprises: receiving, at a data-processing system situated in a telephony network, an input speech signal that is based on a speech input of a user at a telecommunications terminal, the input speech signal having a signal quality characteristic as measured at a point in the network other than at the telecommunications terminal; generating a primary sidetone signal that is based on the input speech signal; modifying the primary sidetone signal at the data-processing system, resulting in a modified sidetone signal that is based on one or more values of the signal quality characteristic; and transmitting the modified sidetone signal to the telecommunications terminal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  depicts a schematic diagram of telecommunications system  100  in accordance with the illustrative embodiment of the present invention. 
           [0016]      FIG. 2  depicts the salient components of data-processing system  104 , which is part of telecommunications system  100 . 
           [0017]      FIG. 3  depicts a flowchart of the salient tasks performed by data-processing system  104 , as part of a first operating scenario, in accordance with the illustrative embodiment. 
           [0018]      FIG. 4  depicts a flowchart of the salient tasks performed by data-processing system  104 , as part of a second operating scenario, in accordance with the illustrative embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 1  depicts a schematic diagram of telecommunications system  100  in accordance with the illustrative embodiment of the present invention. System  100  comprises telecommunications network  101 ; first telecommunications terminal  102 ; and second telecommunications terminal  103 . The elements in system  100  are interconnected as shown. 
         [0020]    Telecommunications network  101  enables the transport and control of communications signals between endpoints such as terminals  102  and  103 . The communications signals convey media signals, such as audio, video, and so forth. To this end, network  101  comprises one or more interconnected data-processing systems such as switches, servers, routers, and gateways, as are well-known in the art. Network  101 , for example, comprises data-processing system  104 , which is described below and with respect to  FIG. 2 . 
         [0021]    In accordance with the illustrative embodiment, network  101  comprises an Internet Protocol-based (IP-based) network, as is known in art, for the purpose of transmitting bitstreams of encoded voice signals. Although network  101  in the illustrative embodiment comprises a Voice-over-IP (VoIP) service provider&#39;s network, network  101  could alternatively or additionally comprise another type of network such as the Internet, some other type of IP-based network, or some other type of packet-based network, as those who are skilled in the art will appreciate. Additionally, it will be clear to those skilled in the art, after reading this specification, how to make and use alternative embodiments of the present invention in which media other than audio is controlled and transported from one terminal to another. 
         [0022]    Telecommunications terminals  102  and  103  are endpoint devices, such as desksets, cellular phones, soft phones resident in computers, personal digital assistants, and so forth. Each of terminals  102  and  103  enables their users to communicate with each other, or with users of other terminals supported by network  101  that are not depicted. Accordingly, terminals  102  and  103  interoperate with network  101  and with each other in well-known fashion. 
         [0023]    Terminal  102 , in accordance with the illustrative embodiment, is a Voice over Internet Protocol (VoIP) phone, which is particularly vulnerable to impairments in signal quality, often because of the bandwidth asymmetry of the data paths between the VoIP terminal and the network infrastructure. Moreover, the particular type of VoIP phone that is part of the illustrative embodiment, namely an enterprise deskset, operates as part of a system in which the sidetone is generated at a data-processing system, such as a private-branch exchange. However, it will be clear to those skilled in the art, after reading this specification, how to make and use alternative embodiments, in which terminal  102  is a type of digital terminal other than a VoIP phone, such as a digital cell phone, or is instead an analog terminal. It will also be clear to those skilled in the art how to make and use other alternative embodiments in which terminal  102  generates its own prior-art sidetone. And as those who are skilled in the art will also appreciate, embodiments of the present invention can be made and used in which the terminals of system  100  operate in various types of networks such as public networks, private networks, and so forth. 
         [0024]    In accordance with the illustrative embodiment, the present invention is directed at a technique that provides, to a first user at a first terminal, feedback on the signal quality being experienced by a second user at a second terminal, wherein both users are humans. In various alternative embodiments, however, the first user might be human and the second user might be a machine, or the first user might be a machine and the second user might be human, and so forth. 
         [0025]    Data-processing system  104  is a communications server that performs one or more functions that enable proper communication between a first and second user. The salient components of system  104  that enable this communication are described below and with respect to  FIG. 2 . System  104  also performs the tasks of the illustrative embodiment, the salient tasks being described below and with respect to  FIGS. 3 and 4 . 
         [0026]    In accordance with the illustrative embodiment, data-processing system  104  is a private-branch exchange (PBX). As those who are skilled in the art will appreciate, however, system  104  can be a central-office switch or another type of network node. 
         [0027]      FIG. 2  depicts the salient components of data-processing system  104 , in accordance with the illustrative embodiment of the present invention. System  104  comprises network interface  201 , processor  202 , and memory  203 , interconnected as shown. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which system  104  comprises any subcombination of the components listed above. 
         [0028]    Network interface  201  comprises the circuitry that enables system  104  to receive signals from and transmit signals to any terminal, such as terminals  102  and  103 , in well-known fashion. 
         [0029]    Processor  202  is a general-purpose processor that is capable of receiving information from and transmitting information to network interface  201 , of executing instructions stored in memory  203  including those that correspond to the tasks of the illustrative embodiment, and of reading data from and writing data into memory  203 . In some alternative embodiments of the present invention, processor  202  might be a special-purpose processor. 
         [0030]    Memory  203  stores the instructions and data used by processor  202 , in well-known fashion. Memory  203  can be any combination of dynamic random-access memory (RAM), flash memory, disk drive memory, and so forth. 
         [0031]    Data-processing system  104  is further capable of producing a “sidetone signal,” as is well-known in the art, which is generated from the speech of the user of a telecommunications terminal and is then fed back to the user as she speaks. Without sidetone, a telecommunications terminal sounds dead to the user while she is speaking; this is because her ear is covered by the terminal&#39;s receiver, which impedes the acoustic path from mouth to ear. 
         [0032]    The sidetone heard by users of wired analog telephones is created within the phone itself by a circuit commonly referred to as the “sidetone hybrid.” This circuit combines four wires within the phone (two for the microphone and two for the speaker) into a pair of wires that carries both the transmit and receive signals. The loudness of the sidetone varies as a function of the impedance mismatch between the telephone and its associated port on a private-branch exchange or switch. 
         [0033]    In certain digital telephony systems such as Voice over Internet Protocol (VoIP), sidetone generation is controlled by software or firmware at a data-processing system separate from the phone, such as system  104 . As is the case with analog telephony, the objective of the sidetone mechanism in these digital systems is to provide users with an accurate representation of their voice while they are speaking. 
         [0034]      FIGS. 3 and 4  depict flowcharts of the salient tasks performed by data-processing system  104 , as part of various operating scenarios, in accordance with the illustrative embodiment of the present invention. As those who are skilled in the art will appreciate, some or all of the individual tasks depicted in  FIGS. 3 and 4  can be performed simultaneously or performed in a different order from that depicted. 
         [0035]    For pedagogical purposes, examples are provided in which terminals  102  and  103  are exchanging communication signals with each other. In the first operating scenario, which is represented by  FIG. 3 , terminal  102  is a VoIP deskset. The signals that are being exchanged traverse data-processing system  104 , which is a private-branch exchange that generates sidetone on behalf of terminal  102 . In the second operating scenario, which is represented by  FIG. 4 , terminal  102  is a phone that generates its own traditional sidetone, such as a cell phone or a POTS analog phone. In the second operating scenario, data-processing system  104 , which is a private-branch exchange, is aware that terminal  102  generates its own traditional sidetone, which can be ascertained in well-known fashion—for example, from terminal-related information that system  104  maintains in its database. 
         [0036]    As those who are skilled in the art will appreciate, alternative embodiments of the present invention can involve, to list a few variations, the exchange of other types of media content such as video; more than two terminals communicating with one another, either as part of the same session or across multiple, simultaneous sessions; different types of telecommunications terminals than those in the illustrative embodiment; and/or a different type of data-processing system that either does or does not provide traditional sidetone. 
         [0037]      FIG. 3  depicts a flowchart of the salient tasks performed by data-processing system  104 , as part of the first operating scenario in which system  104  generates traditional sidetone. At task  301 , system  104  receives an input speech signal represented in a bitstream originating from terminal  102 . The input speech signal is based on a speech input of terminal  102 &#39;s user. At least some of the bits in the bitstream received by data-processing system  104  are also transmitted to terminal  103  and intended for its user. 
         [0038]    In accordance with the illustrative embodiment, the bitstream comprises audio information. In some alternative embodiments, the bitstream might comprise video information, audio and video information, or some other type of media content. In still other alternative embodiments, the bitstream might also comprise information that is already being collected by network  101  about one or more portions of the communications path from terminal  102 . 
         [0039]    At task  302 , system  104  obtains (i.e., generates or receives) one or more values of quality statistics in well-known fashion, where each quality statistic obtained is based on at least a portion of the input speech signal received at task  601 . Each quality statistic obtained is related to a signal quality characteristic from the general categories of i) quality of service (QoS) and ii) media waveform quality, sometimes referred to as “quality of media” (QoM). Quality statistics that are associated with quality of service are those which are a measure of the bandwidth, error rate, and/or latency from one node to another. 
         [0040]    Quality statistics that are associated with media waveform quality are those which are a measure of how well a media signal that is received at a device compares with what is required to be received at that device, when assessed at the waveform level. A media signal can be an audio signal, a video signal, a modem traffic signal, a TTY signal, a facsimile signal, or some other signal that can be characterized as having a waveform. The device can be the intended destination of the media signal within a telecommunications system or it can be an intermediate node within the telecommunications system, such as data-processing system  104 . 
         [0041]    Waveform quality is distinguished from quality of service, in that quality of service is a measure that is performed at the bit or packet level. Waveform quality is a function of, but is not limited to, one or more of the following waveform characteristics:
       i. loudness,   ii. audio distortion,   iii. noise,   iv. fading,   v. crosstalk, and   vi. echo.       
 
         [0048]    As those who are skilled in the art will appreciate, quality statistics that are generated in accordance with the illustrative embodiment can also be related to other performance characteristics that have to do with signal quality. Furthermore, in some alternative embodiments, some or all of the quality statistics can be generated from information that is already being collected about one or more portions of the communications path from terminal  102 , as described above and with respect to task  301 . 
         [0049]    At task  303 , system  104  generates a traditional sidetone signal in well-known fashion. For purposes of clarity, the sidetone signal generated at task  303  is referred to as the “primary” sidetone signal in the remaining tasks related to  FIG. 3 . 
         [0050]    At task  304 , system  104  modifies the primary sidetone signal generated at task  303 , resulting in a “modified” sidetone signal. The modification of the primary sidetone signal is based on an assessment of the severity and nature of audio quality impairments in the received input speech signal, as represented by the measured signal quality characteristics described above and with respect to task  302 . 
         [0051]    In a first example of modifying the primary sidetone, if the signal quality (e.g., bit-error rate, etc.) statistics obtained by system  104  indicate that the incoming speech is degraded beyond a predetermined threshold level, the operation at task  304  adds a delayed version of the sidetone to the primary sidetone generated at task  303 . As those who are skilled in the art will appreciate, the delay amount, which can be as little as a few milliseconds to be effective (e.g., 5 to 20 milliseconds, etc.), can be selected so that to terminal  102 &#39;s user the modified sidetone sounds “hollow” and objectionable. A hollow-sounding sidetone might sound to the user as if she is speaking with her head inside a rain barrel, on account of the different frequency components of her voice being either emphasized or canceled out in the sidetone. 
         [0052]    In some embodiments, different delay amounts can be used to achieve other acoustic effects (e.g., reverb, echo, etc.), as those who are skilled in the art will appreciate. Additionally, in some embodiments, the relative amplitudes of the delayed sidetone signal and the primary sidetone signal can be varied, in order to achieve additional effects. 
         [0053]    In a second example of modifying the primary sidetone, system  104  changes the amplitude of the primary sidetone. For instance, system  104  can indicate a transient interruption of transmissions to the far-end user—an interruption of the sort that occurs frequently with wireless terminals—by imposing a corresponding, noticeable drop of sidetone amplitude according to a predetermined attenuation. 
         [0054]    In a third example of modifying the primary sidetone, system  104  adds noise, or some other type of objectionable sound, to the primary sidetone signal when the signal quality statistics obtained by system  104  indicate that the incoming speech is degraded beyond a predetermined threshold level. Examples of noise that can be added are white noise, colored noise, clicks, pops, hum, and so forth. 
         [0055]    In some embodiments, system  104  varies a characteristic of the noise that is added to the sidetone signal, based on how much the signal degradation exceeds the applicable predetermined threshold. For example, the amplitude or frequency bandwidth of the noise can be varied in proportion to the variation of the degree of degradation as reflected in the signal quality statistics obtained at task  302 . 
         [0056]    As those who are skilled in the art will appreciate, the components of the modified sidetone signal can be different than those described, and in various ways. First, multiple added or altered components (e.g., delayed sidetone, amplitude change, noise, other distortion, etc.) can be present in the same modified sidetone. Second, each additional component can be added to the primary sidetone based on a different threshold level for a given signal characteristic. Third, each component that is added or altered can be a function of more than one signal quality characteristic or can even be a function of a parameter other than a signal quality characteristic. And fourth, the implementation or characteristics, or both, of each addition or alteration can be based on a different signal quality characteristic from one component to another. 
         [0057]    Conversely to modifying the primary sidetone at task  304 , if the signal quality statistics indicate that the incoming speech is of an acceptable quality, as determined by the statistic being within the applicable predetermined threshold for the particular signal quality characteristic being assessed, then the operation at task  304  refrains from modifying the primary sidetone signal. 
         [0058]    At task  305 , system  104  transmits the modified sidetone signal, or the primary sidetone signal if no modification has been made, to terminal  102  for the terminal&#39;s user to hear. 
         [0059]    Data-processing system  104  continually performs the tasks described with respect to  FIG. 3  throughout the call between terminals  102  and  103 , and can also perform the described set of tasks concurrently for other calls involving other terminals as well. Furthermore, system  104  can also perform the tasks bi-directionally for a given call, so that the user of terminal  103  is also provided sidetone feedback on the signal quality that is being experienced by the user of terminal  102 . 
         [0060]      FIG. 4  depicts a flowchart of the salient tasks performed by data-processing system  104 , as part of the second operating scenario in which traditional sidetone is generated somewhere other than at system  104 , which generates a supplemental sidetone and/or noise in accordance with the illustrative embodiment. At task  401 , system  104  receives an input speech signal (e.g., in the form of a bitstream, an analog waveform, etc.) originating from terminal  102 , as described above and with respect to task  301 . 
         [0061]    At task  402 , system  104  obtains (i.e., generates or receives) one or more quality statistics in well-known fashion, as described above and with respect to task  302 . 
         [0062]    At task  403 , system  104  generates a first sidetone signal (i.e., supplemental sidetone) based on the measured signal quality characteristic as represented by the quality statistics obtained at task  402 . In accordance with the illustrative embodiment, system  104  generates the first sidetone signal so that when transmitted to the telecommunications terminal (as described below and with respect to task  405 ), the first sidetone signal arrives at a handset receiver at the telecommunications terminal with a predetermined delay in relation to a second sidetone signal arriving at the handset receiver. The second sidetone signal is a traditional sidetone signal that is generated for the telecommunications terminal in well-known fashion-for example, by the terminal itself. 
         [0063]    As those who are skilled in the art will appreciate, the predetermined delay amount, which can be as little as a few milliseconds to be effective (e.g., 5 to 20 milliseconds, etc.), can be selected so that to terminal  102 &#39;s user the overall sidetone—that is, the combination of the system  104 -generated sidetone and the traditional sidetone generated elsewhere—sounds “hollow” and objectionable. It will be clear to those skilled in the art how to determine the sources of delay throughout telecommunications network  101 , in order to implement the desired delay at the reference point of the handset receiver. 
         [0064]    In some embodiments, different delay amounts can be used to achieve other acoustic effects (e.g., reverb, echo, etc.), as those who are skilled in the art will appreciate. Additionally, in some embodiments, the amplitude of the system  104 —generated sidetone signal can be increased or decreased, in order to achieve additional effects. 
         [0065]    Conversely to generating the supplemental sidetone at task  403 , if the signal quality statistics indicate that the incoming speech is of an acceptable quality, as determined by the statistic being within the applicable predetermined threshold for the particular signal quality characteristic being assessed, then the operation at task  403  refrains from generating the supplemental sidetone signal. 
         [0066]    At task  404 , system  104  adds noise, or some other type of objectionable sound, to the sidetone signal when the signal quality statistics obtained by system  104  indicate that the incoming speech is degraded beyond a predetermined threshold level. Examples of noise that can be added are white noise, colored noise, clicks, pops, hum, and so forth. Alternatively, the noise can be introduced in the absence of any generated sidetone signal. 
         [0067]    In some embodiments, system  104  varies a characteristic of the noise that is added to the sidetone signal, based on how much the signal degradation exceeds the applicable predetermined threshold. For example, the amplitude or frequency bandwidth of the noise can be varied in proportion to the variation of the degree of degradation as reflected in the signal quality statistics obtained at task  402 . 
         [0068]    As those who are skilled in the art will appreciate, the generated supplemental sidetone component and/or added noise component can be different than described above. Each component can be introduced based on a different threshold level for a given signal characteristic. Also, each component added or altered can be a function of more than one signal quality characteristic or can even be a function of a parameter other than a signal quality characteristic. Finally, the implementation and/or characteristics of each component introduced can be based on a different signal quality characteristic from one component to another. 
         [0069]    At task  405 , system  104  transmits the generated supplemental sidetone and/or noise to terminal  102  for the terminal&#39;s user to hear. 
         [0070]    Data-processing system  104  continually performs the tasks described with respect to  FIG. 4  throughout the call between terminals  102  and  103 , and can also perform the described set of tasks concurrently for other calls involving other terminals as well. Furthermore, system  104  can also perform the tasks bi-directionally for a given call, so that the user of terminal  103  is also provided sidetone feedback on the quality that is being experienced by the user of terminal  102 . 
         [0071]    In accordance with the illustrative embodiment, system  104  affects the sidetone signal provided to the user of terminal  102 , based at least in part on one or more signal quality statistics for the audio in the corresponding transmit path (i.e., in the direction from terminal  102  towards terminal  103 ). However, it will be clear to those skilled in the art, after reading this specification, how to make and use alternative embodiments of the present invention in which the sidetone signal is affected based on signal quality statistics for the audio transmitted over a non-corresponding path (e.g., an audio path between another pair of terminals, an audio path between terminal  102  and a third terminal, etc.). 
         [0072]    Additionally, it will be clear to those skilled in the art, after reading this specification, how to make and use alternative embodiments of the present invention in which the sidetone signal is affected based on quality statistics for a non-audio type of media (e.g., video, etc.) that is transmitted over a signal path between two terminals (e.g., terminals  102  and  103 , terminal  102  and a third terminal, two other terminals, etc.). 
         [0073]    It is to be understood that the disclosure teaches just one example of the illustrative embodiment and that many variations of the invention can easily be devised by those skilled in the art after reading this disclosure and that the scope of the present invention is to be determined by the following claims.