Abstract:
The present invention provides an indication to the user of a voice communication system that an echo at the user&#39;s location has been detected by the system. In response to receiving this indication of echo, users may take any of several actions to reduce the echo, such as changing the position of the microphone or changing their own position with respect to the microphone. The need for potentially expensive echo-canceling hardware and software is reduced because the actions to eliminate the echo are performed by the user. The echo detector in the present invention may be implemented as part of a voice terminal, or as part of a communication switch or server that is used in conjunction with a voice terminal.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to providing an indication of the presence of an echo in an outgoing telephone signal. In particular, the present invention relates to providing a user with an indication that echo is present in a signal, so that a user can take appropriate action. 
     BACKGROUND OF THE INVENTION 
     Voice communication systems, including telephone systems, are subject to several sources of echo that make transmitted voices sound bad to listeners. These echoes can noticeably degrade the intelligibility and quality of the transmitted voice signal. One source of echo is simple acoustic reverberation at the talker&#39;s physical location. Echoes associated with acoustic reverberation at the talker&#39;s physical location are particularly evident in connection with speaker phones. However, it is often the case that people speaking into a speakerphone within small enclosed environments, such as offices or conference rooms, are unaware of such echoes. 
     Attempts at reducing echo in transmitted voices have included physically modifying room acoustics. Such physical modifications can be made by, for example, placing echo dampening material on the walls and ceilings. However, such modifications can be expensive. In addition, such modifications may not be possible or appropriate to all rooms in which the use of a speaker phone is desirable. Furthermore, a change in the arrangement of furniture in a room, or in the position of the speaker phone within the room, can result in the introduction of echo to a transmitted voice signal, even though previously there had been no echo. 
     Other attempts at reducing echo in outgoing signals have included placing individual microphones as close as possible to talkers. For example, requiring talkers to speak into microphones positioned directly in front of the talker&#39;s mouth, for example as part of a handset or headset, can be effective in reducing acoustic echo. However, it is not always convenient or desirable to hold a handset or to wear a headset. Furthermore, although microphones can be placed in front of individual talkers, for example in a conference call scenario with multiple talkers at a location using a speaker phone, the problem of acoustic reverberation at the physical location may not be entirely avoided. 
     Still another attempt at reducing the effect of echo or acoustic reverberation in outgoing voice communication signals is the use of highly directional microphone designs. Directional microphones may be deployed singly or in arrays, and are capable of accepting or rejecting sounds depending on their point of origin. However, directional microphones are relatively expensive, can be difficult to properly set up, and do not work well when a talker is moving about their physical location. 
     Yet another attempt at reducing echo in voice communications is the use of signal processing techniques to compensate for or remove the echo. Generally, such techniques require the deployment of a digital signal processor capable of detecting and compensating for the echo. Although such techniques can be effective at reducing the effects of acoustic reverberation, they are relatively expensive to develop and deploy. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to solving these and other problems and disadvantages of the prior art. Generally, according to the present invention, the presence of acoustic reverberation or echo in a voice signal is detected. The user or talker is then notified of the acoustic reverberation, so that the user can take appropriate steps to mitigate the acoustic reverberation. For example, in response to receiving an indication that acoustic reverberation is present, the user may change their position, the position of the microphone receiving the voice signal provided by the user may be changed, or both the user&#39;s and the microphone&#39;s physical location may be altered. If an initial change in the physical location of the user and/or the microphone is not effective in removing the echo, the user may continue to alter their position and/or the position of the microphone until the presence of acoustic reverberation in the transmitted voice signal is eliminated or reduced. 
     In accordance with an embodiment of the present invention, a voice signal provided by a user is converted into an electronic signal by a microphone. The electronic signal is then provided to an echo detector. If the echo detector determines that there is an echo in the transmitted voice signal, an output signal notifying the user of the presence of echo is provided. In accordance with an embodiment of the present invention, the output signal comprises a visual indication of the presence of an echo. In accordance with another embodiment of the present invention, the presence of echo is provided by an audible signal. In accordance with still another embodiment of the present invention, the output signal provides an indication of the magnitude of the detected echo. 
     In accordance with an embodiment of the present invention, the components of a system for providing an indication of the presence of an echo in a transmitted voice signal are provided as part of a voice terminal. For example, such a system may be provided as part of a speaker phone. As a further example, the system may be provided as part of or in connection with a soft telephone. 
     In accordance with yet another embodiment of the present invention, certain components or features of a system for providing an indication of the presence of an echo may be provided by a voice terminal, while other components or features are provided by an interconnected communications server or switch. For example, an electronic representation of a voice signal provided by a user may be generated in a voice terminal, and the detection of an echo in the transmitted voice signal may be performed in a communication server. The communication sever may signal the voice terminal that echo has been detected, and the user may in turn be provided with an indication of the presence of echo by the voice terminal. 
     These and other advantages and features of the invention will become more apparent from the following discussion, particularly when taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  depicts the physical relationship between a user and a voice terminal in a room in a first example; 
         FIG. 1B  depicts the physical relationship between a user and a voice terminal in a room in accordance with another example; 
         FIG. 1C  depicts the physical relationship between a user and a voice terminal in a room in accordance with still another example; 
         FIG. 2A  depicts a system for providing an indication of echo in a transmitted voice communication in accordance with an embodiment of the present invention; 
         FIG. 2B  depicts another system for providing an indication of echo in a transmitted voice communication in accordance with another embodiment of the present invention; 
         FIG. 3  is a flowchart depicting the operation of a system for providing an indication of echo to a user in accordance with an embodiment of the present invention; and 
         FIG. 4  is a flowchart depicting a method for reducing echo in a transmitted voice signal in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is directed to signaling the presence of echo in a transmitted voice signal to a user. 
     In  FIGS. 1A to 1C , examples of different relative positions of a user or talker  104  and a voice terminal or voice communication device  108  within a room  112  are shown. In addition, a first wall  116  and a second wall  120  of the room  112  are illustrated. The voice terminal  108  generally includes a far talk microphone  124  and a broadcast speaker  128  for facilitating speaker phone operation. In addition, the voice terminal  108  illustrated in  FIGS. 1A to 1C  includes a key pad  132 , a display  136 , and a handset  140 . The handset  140  in turn includes a microphone  144  and a speaker  148 . As can be appreciated, not all of the features  124 – 148  illustrated in connection with the voice terminal  108  as shown in  FIGS. 1A–1C  must be provided. Furthermore, additional features may be provided if desired. 
     The voice terminal  108  may generally comprise a conventional telephone or speaker phone. In addition, the voice terminal  108  may comprise a soft or Internet protocol (IP) telephone. In general, the far talk microphone  124 , if provided, is configured for receiving voice signals provided by a user even if the far talk microphone  124  is not positioned directly in front of the user&#39;s mouth. The broadcast speaker  128  is generally configured for providing audible output to the user  104  even if the user&#39;s ear is not positioned directly in front of the speaker  128 . The handset  140  generally provides a microphone  144  and a speaker  148  that are configured for use when positioned generally in front of the user&#39;s mouth and ear, respectively. As can be appreciated, the voice terminal  108  may provide various alternative combinations of microphones  124 ,  144  and speakers  128 ,  148 . 
     The keypad  132  may include any device suitable for receiving input from the user  104 . Accordingly, the keypad  132  may include a numeric keypad or a textual keypad. In addition, the user input functions of the keypad may be performed in connection with a voice recognition algorithm provided by the voice terminal  108  or an interconnected communication server or switch. The display  136  may include a numeric display, bar graph, colored and/or labeled indicator lights, or a configurable display comprising, for example, a cathode ray tube or a liquid crystal display. As can also be appreciated, functions of the keypad  132  and display  136  can be combined, for example in the form of a touch screen. 
     As can be appreciated by one of skill in the art, acoustic reverberation may result in the transmission of an echo together with a voice signal provided to a voice terminal  108  by a user  104 , particularly in connection with voice signals provided through the far talk microphone  124 . Such acoustic reverberation may result from features found at the physical location of the voice terminal  108 . For instance, in the examples illustrated in  FIGS. 1A–1C , the walls  116 ,  120  of the room  112  can reflect the user&#39;s  104  voice. Because the reflected voice signal is delayed as compared to the voice signal that travels directly from the mouth of the user  104  to the microphone  124  or  144 , the reflected signal can be perceived as an echo in the transmitted voice signal. Furthermore, features in the room  112  such as the finish of the walls  116 ,  120 , floor coverings, furniture, the position and presence of windows, etc. can all influence the presence and magnitude of acoustic reverberations that result in a perceptible echo. Accordingly, it is difficult to position a user  104  and a voice terminal  108  in a room  112  such that an echo free transmitted voice signal can be assured. In addition, changes to the room  112 , for example the opening or closing of a window, window covering, or door, can change the acoustic characteristics of the room  112 , thereby altering the position or positions of the user  104  and voice terminal  108  at which echo in the transmitted signal is minimized or held to an acceptable level. 
     With reference now to  FIGS. 2A and 2B , systems  200 ,  202  having features for providing an indication of echo in a voice transmission in accordance with an embodiment of the present invention are illustrated in block diagram form. The systems  200 ,  202  generally include a microphone  204 , an echo detector  208  and a user output  212 . The microphone  204  generally functions as a transceiver that generates digital or analog representations of voice signals received from the user  104 , and may comprise a far talk microphone  124  and/or a near talk microphone  144 . The echo detector  208  may include a processor  216  and memory  220 . In the embodiment illustrated in  FIG. 2A , the echo detector  208  is provided as part of a voice terminal  108 . As shown in  FIG. 2B , the echo detector  208  may also be provided as part of a device  224  that is separate from the voice terminal  108 . For example, the device  224  may comprise a communication server or a switch. As a further example, the device  224  may comprise a computer terminal, such as a computer terminal provided in connection with a voice terminal  108 , comprising a soft or Internet protocol (IP) telephone. In accordance with an embodiment of the present invention, the processor  216  is a digital signal processor. The memory  220  may be any electronic memory suitable for storing information for use in connection with the operation of the processor  216 . For instance, the memory  220  may be used to store programming code that is run on the processor  216  to perform the echo detection of function. In accordance with still another embodiment of the present invention, the echo detector  208 , and in particular the processor  216  and memory  220  may be implemented as part of a single integrated circuit, including a controller. 
     The echo detector  208  analyzes the voice signal received from the microphone  204  to detect the presence of echo. For instance, the echo detector  208  may take a digital representation of a voice signal received from the microphone  204 , and provide it to the processor  216 , for detection of rippling in the spectral content of the received signal. Alternatively, the processor  216  may determine the presence of echos in the signal directly. The processor  216  may also determine a magnitude of an echo detected in the voice signal. As can be appreciated, the echo detector  208  may additionally comprise an analog to digital converter where an analog signal is received from the microphone  204 . 
     The user output  212  provides an indication to the user  104  regarding the presence of echo in the transmitted voice signal. The user output  212  may provide a visual, audible, or both a visual and audible indication to the user  104 . In addition, the user output  212  may simply provide an indication that echo has been detected, or it may additionally provide an indication of the magnitude of the detected echo. For example, the user output  212  may comprise a numerical output for communicating the magnitude of the detected echo. In connection with an audible output  212 , a beeping tone that changes frequency with a change in the magnitude of the detected echo may be provided. In accordance with an embodiment of the present invention, the user output  212  is provided by a display  136  included as part of the voice terminal  108  (See  FIGS. 1A–1C ). In accordance with another embodiment of the present invention, the user output  212  is provided by the speaker  128  or  148  of the voice terminal  108  (See  FIGS. 1A–1C ). 
     With reference now to  FIG. 3 , the operation of a system  200  in accordance with an embodiment of the present invention is shown. Initially, at step  300 , an audible signal is received from a user or user  104 . A determination is then made as to whether the presence of an echo is detected in the voice signal (step  304 ). As mentioned above, the presence of an echo in the voice signal may be determined in a variety of ways known to those of skill in the art. For example, a ripple or perturbation in the spectral content of the received voice signal may provide an indication of echo in that signal. As a further example, the receipt of a duplicate, time delayed signal may be detected as part of the voice signal, and may result in an indication that echo has been detected if the magnitude of the time delayed signal is found to be large enough that the psycho-acoustic effect of the detected echo associated with the voice signal is significant. 
     In response to a determination that echo is present in the voice signal, a signal indicating the presence of echo is provided to the user  104  (step  308 ). As noted above, the signal may be provided as a visual indication, an audible indication, or both a visual and audible indication. For example, a visual indication may be provided in a display  136  included in the voice terminal  108  (See  FIGS. 1A–1C ). Furthermore, the signal may include an indication of the detected magnitude of the echo, for example in a numeric or sliding bar form. Furthermore, the detection of echo may be signaled by a user output  212  comprising the speaker  128  or  148  of the voice terminal  108 . (See  FIGS. 1A–1C ). An embodiment that provides an audible output is particularly useful in connection with a voice terminal  108  that does not provide a visual display  136 . 
     After the detection of an echo has been signaled to the user  104  (step  308 ), the system returns to step  300 . Accordingly, it can be appreciated that, in accordance with an embodiment of the present invention, the voice signal received from the user  104  is continually monitored for the presence of echo. In response to a failure to detect the presence of echo in a voice signal at step  304 , the absence of an echo may be signaled to the user  104  (step  312 ). The absence of a signal may be provided in a positive fashion by the user output  212 . Alternatively, the absence of echo may be signaled by providing no signal to the user  104  regarding echo. That is, a positive output may be provided to a user  104  only when echo having a potentially significant psycho-acoustic effect is detected in connection with a voice signal. Following step  312 , the system returns to step  300 . Accordingly, it can be appreciated that, in connection with an embodiment of the present invention, the voice signal is continually monitored for the presence of echo. 
     With reference now to  FIG. 4 , a method for reducing echo in a voice signal for use in connection with a system  200  in accordance with the present invention is shown. Initially, at step  400 , the voice terminal  108  is activated. For example, the voice terminal  108  may be placed off hook by pressing an appropriate button provided as part of a key pad  132 . Alternatively, the receiver  140  may be lifted. At step  404 , the user  104  talks into the voice terminal  108 . That is, the user  104  provides a voice signal that is detected by the microphone  124  or  144 . At step  408 , a determination is made as to whether echo is detected, and the user  104  is signaled accordingly. That is, steps  304 ,  308  and  312  described above in connection with  FIG. 3  are performed. If no echo is detected, the user  104  continues to provide the voice signal normally. That is, the user  104  may continue with a voice communication using the voice terminal  108  with the assurance that there is no significant echo in the provided voice signal, at least as provided from the user  104  to the voice terminal  108 . 
     If echo is detected and signaled to the user  104 , the user may alter the position of the voice terminal  108 , or the user  104  may alter their position relative to the voice terminal  108  (step  412 ). Furthermore, both the position of the user  104  and of the voice terminal  108  may be altered. For example, the user  104  and the voice terminal  108  may be positioned in a room  112  as shown in  FIG. 1A . In response to receiving a indication that echo is present in the voice signal, the user  104  may alter their position and the position of the voice terminal  108  in the room  112 , to the positions shown in  FIG. 1B . 
     After altering the position of the voice terminal  108  and/or the user  104 , the user  104  may continue talk into the voice terminal  108  (step  404 ). The system may then return to step  408  to determine whether echo continues to be detected in the voice signal. If no echo is detected, the user  104  may continue talk into the voice terminal  108  with assurance that any echo associated with the voice signal is not psycho-acoustically significant. 
     If echo continues to be detected, the system will return to step  412 , and the user  104  may again alter the position of the voice terminal  108  and/or the user  104 . For example, the user may change their position and the position of the voice terminal  108  from the position shown in  FIG. 1B  to the position shown in  FIG. 1C . The user  104  may then continue to talk into the voice terminal  108  (step  404 ) and a determination as to whether echo is detected (step  408 ) may again be made. This process may continue for as long as the user  104  provides a voice signal to the terminal  108 , until the user  104  turns off the echo detection feature, or until the user  104  decides to stop making adjustments in response to the echo detection signal. 
     From the description provided herein, it can be appreciated that a user  104  may adjust their position or the position of a voice terminal  108  continually while providing a voice signal until an echo associated with the voice signal and resulting from acoustic reverberations at the physical location (e.g., the room  112 ) of the user  104  and the voice terminal  108  is eliminated or reduced. Furthermore, it can be appreciated that the monitoring for echo within a voice signal may be continuous, and that the user  104  may change their position relative to the voice terminal  108  as desired if an indication of echo is received. 
     As noted above, the echo detector  208  may be provided as part of a communication network provider switch or communication server  224 . In connection with such an embodiment, the provision of an audible user output  212  (e.g., through speaker  128  or  148 ) is particularly useful. Alternatively or in addition, in connection with an embodiment in which the echo detector is located  208  at a site remote from the voice terminal  108 , an out of band signal may be provided to the voice terminal to signal the presence of echo, and an output  212  signaling to the user  104  that echo has been detected may be provided. 
     The present invention may be utilized in connection with standard switched circuit telephony network. For instance, the present invention may be utilized with a voice terminal  108  comprising a standard speaker phone or telephone. Furthermore, where the echo detection function is provided as part of the voice terminal  108 , a processor  216  associated with the voice terminal  108  may be modified to perform the echo detector  208  function, or a processor  216  may be especially provided to perform the echo detector  208  function. As can be appreciated, the present invention is particular useful in connection with voice terminals  108  used as speaker phones. However, the present invention may also be utilized to detect echos associated with voice signals received by microphones  144  provided as part of handsets  140  or headsets. 
     In addition to use in connection with switched telephony circuits, the present invention may be utilized in connection with voice terminals  108  communicating over packet data networks, including the Internet. Furthermore, because of the significant degradation of sound quality that can occur when voice signals transmitted over VoIP networks has an associated echo, the present invention is particularly useful in connection with such networks. 
     The foregoing discussion of the invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, within the skill and knowledge of the relevant art, are within the scope of the present invention. The embodiments described hereinabove are further intended to explain the best mode presently known of practicing the invention and to enable others skilled in the art to utilize the invention in such or in other embodiments and with various modifications required by their particular application or use of the invention. It is intended that the appended claims be construed to include the alternative embodiments to the extent permitted by the prior art.