Apparatus and method for canceling acoustic echoes including non-linear distortions in loudspeaker telephones
First Claim
1. An echo canceling loudspeaker telephone comprising:
- a loudspeaker for producing a sound pressure wave in response to an input signal which is applied to an audio input thereof, said sound pressure wave including a desired linear component which is a linear function of said input signal, and an undesired non-linear component which is a non-linear function of said input signal, said sound pressure wave being transmitted along an acoustic path;
a microphone positioned in said acoustic path for converting said sound pressure wave into an output signal;
an echo filter responsive to said input signal and which generates an estimated echo signal, said echo filter comprising a loudspeaker model which generates an estimate of said sound pressure wave including an estimate of said linear component and an estimate of said non-linear component, and an acoustic path model which generates an estimate of said acoustic path from said loudspeaker to said microphone;
a subtractor for subtracting said estimated echo signal from said output signal thereby reducing an echo portion of said output signal; and
an echo filter modifier responsive to said output signal said input signal and said estimated echo signal which determines a residual echo portion of said output signal remaining after subtracting said estimated echo signal from said output signal, and which modifies estimates of distortions due to said loudspeaker and said acoustic path in response to said residual echo portion to further reduce said echo portion of said output signal;
wherein said loudspeaker model and said acoustic path model are connected in series.
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Accused Products
Abstract
An echo canceling loudspeaker telephone includes a loudspeaker which produces a sound pressure wave in response to an input signal which is applied to an audio input thereof. This sound pressure wave includes a desired linear component which is a linear function of the input signal, and an undesired non-linear component which is a non-linear function of the input signal, and the sound pressure wave is transmitted along an acoustic path. A microphone is positioned in the acoustic path and converts the sound pressure wave into an output signal. An echo filter is responsive to the input signal and generates an estimated echo signal. This echo filter includes a loudspeaker model which generates an estimate of the sound pressure wave including an estimate of the linear component and an estimate of the non-linear component. This echo filter also includes an acoustic path model which generates an estimate of the acoustic path from the loudspeaker to the microphone. In addition, a subtractor subtracts the estimated echo signal from the output signal thereby reducing an echo portion of said sound signal.
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Citations
31 Claims
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1. An echo canceling loudspeaker telephone comprising:
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a loudspeaker for producing a sound pressure wave in response to an input signal which is applied to an audio input thereof, said sound pressure wave including a desired linear component which is a linear function of said input signal, and an undesired non-linear component which is a non-linear function of said input signal, said sound pressure wave being transmitted along an acoustic path; a microphone positioned in said acoustic path for converting said sound pressure wave into an output signal; an echo filter responsive to said input signal and which generates an estimated echo signal, said echo filter comprising a loudspeaker model which generates an estimate of said sound pressure wave including an estimate of said linear component and an estimate of said non-linear component, and an acoustic path model which generates an estimate of said acoustic path from said loudspeaker to said microphone; a subtractor for subtracting said estimated echo signal from said output signal thereby reducing an echo portion of said output signal; and an echo filter modifier responsive to said output signal said input signal and said estimated echo signal which determines a residual echo portion of said output signal remaining after subtracting said estimated echo signal from said output signal, and which modifies estimates of distortions due to said loudspeaker and said acoustic path in response to said residual echo portion to further reduce said echo portion of said output signal; wherein said loudspeaker model and said acoustic path model are connected in series. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An echo canceling loudspeaker telephone comprising:
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a loudspeaker for producing a sound pressure wave in response to an input signal which is applied to an audio input thereof, said sound pressure wave including a desired linear component which is a linear function of said input signal, and an undesired non-linear component which is a non-linear function of said input signal, said sound pressure wave being transmitted along an acoustic path; a microphone positioned in said acoustic path for converting said sound pressure wave into an output signal; an echo filter responsive to said input signal and which generates an estimated echo signal, said echo filter comprising a loudspeaker model which generates an estimate of said sound pressure wave including an estimate of said linear component and an estimate of said non-linear component, and an acoustic path model comprising a first processing block for generating an estimate of said acoustic path for said non-linear component of said sound pressure wave and a second processing block for generating an estimate of said acoustic path for said linear component of said sound pressure wave; and a subtractor for subtracting said estimated echo signal from said output signal thereby reducing an echo portion of said sound signal. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. An echo-canceling loudspeaker telephone comprising:
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output transducer means for producing a sound pressure wave in response to an input signal which is applied to an audio input thereof, said sound pressure wave including a desired linear component which is a linear function of said input signal, and an undesired non-linear component which is a non-linear function of said input signal, said sound pressure wave being transmitted along an acoustic path; input transducer means positioned in said acoustic path for converting said sound pressure wave into a output signal; echo filter means responsive to said input signal for generating an estimated echo signal, said echo filter means comprising an output transducer model for generating an estimate of said sound pressure wave including an estimate of said linear component and an estimate of said non-linear component, and an acoustic path model for generating an estimate of said acoustic path from said output transducer means to said input transducer means; combination means for combining said estimated echo signal and said output signal thereby reducing an echo portion of said output signal; and an echo filter modifier responsive to said output signal, said input signal and said estimated echo signal which determines a residual echo portion of said output signal remaining after subtracting said estimated echo signal from said output signal, and which modifies estimates of distortions due to said loudspeaker and said acoustic path in response to said residual echo portion to further reduce said echo portion of said output signal. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. An echo-canceling loudspeaker telephone comprising:
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output transducer means for producing a sound pressure wave in response to an input signal which is applied to an audio input thereof, said sound pressure wave including a desired linear component which is a linear function of said input signal, and an undesired non-linear component which is a non-linear function of said input signal, said sound pressure wave being transmitted along an acoustic path; input transducer means positioned in said acoustic path for converting said sound pressure wave into a output signal; echo filter means responsive to said input signal for generating an estimated echo signal, said echo filter means comprising an output transducer model for generating an estimate of said sound pressure wave including an estimate of said linear component and an estimate of said non-linear component, and an acoustic path model for generating an estimate of said acoustic path from said output transducer means to said input transducer means; and combination means for combining said estimated echo signal and said output signal thereby reducing an echo portion of said output signal; wherein said acoustic path model comprises a first processing block for generating an estimate of said acoustic path for said non-linear component of said sound pressure wave and a second processing block for generating an estimate of said acoustic path for said linear component of said sound pressure wave.
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28. A method for reducing echoes in a telephone system including a loudspeaker, said method comprising the steps of:
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applying an input signal to said loudspeaker to produce a sound pressure wave which is transmitted along an acoustic path, said sound pressure wave including a desired linear component which is a linear function of said input signal and an undesired non-linear component which is a non-linear function of said input signal; converting said sound pressure wave in said acoustic path to produce an output signal including an echo portion; generating an estimated echo signal in response to said input signal, wherein said estimated echo signal includes an estimate of distortions due to said loudspeaker which includes linear and non-linear components, and an estimate of distortions due to said acoustic path; and combining said output signal and said estimated echo signal to reduce said echo portion of said output signal; wherein said combining step is followed by the steps of determining a residual echo portion of said output signal remaining after said combining step, and modifying said estimates of distortions due to said loudspeaker and said acoustic path in response to said residual echo portion to further reduce said echo portion of said output signal. - View Dependent Claims (29, 30)
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31. An echo canceling loudspeaker telephone comprising:
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a loudspeaker for producing a sound pressure wave in response to an input signal which is applied to an audio input thereof, said sound pressure wave including a desired linear component which is a linear function of said input signal, and an undesired non-linear component which is a non-linear function of said input signal, said sound pressure wave being transmitted along an acoustic path; a microphone positioned in said acoustic path for converting said sound pressure wave into an output signal; an echo filter responsive to said input signal and which generates an estimated echo signal, said echo filter comprising a loudspeaker model which generates an estimate of said sound pressure wave including an estimate of said linear component and an estimate of said non-linear component, and an acoustic path model which generates an estimate of said acoustic path from said loudspeaker to said microphone; and a subtractor for subtracting said estimated echo signal from said output signal thereby reducing an echo portion of said output signal; wherein said loudspeaker model and said acoustic path model are connected in series; and wherein said acoustic path model comprises a first processing block for generating an estimate of said acoustic path for said non-linear component of said sound pressure wave and a second processing block for generating an estimate of said acoustic path for said linear component of said sound pressure wave.
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Specification