Acoustic echo canceler

• US 5,859,914 A
• Filed: 07/18/1997
• Issued: 01/12/1999
• Est. Priority Date: 07/23/1996
• Status: Expired due to Term

• Current Assignee: Lenovo Innovations Ltd Hong Kong (Lenovo Group Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Ono, Yoshihiro, Ono, Shigeru
• Primary Examiner(s): Harvey, Minsun Oh
• Application Number:
  US08/897,066
• Time in Patent Office: 543 Days
• Field of Search: 381/66, 381/61, 381/94.1, 381/93.3, 381/71.1, 379/406, 379/410, 379/409
• US Class Current: 381/66
• CPC Class Codes: H04M 9/082 using echo cancellers echo cancellers per se H04B3/23

Abstract

The invention provides an acoustic echo canceler which realizes sufficient echo suppression processing on an auditory sense which matches with an amount of calculation and realizes a good speech quality. The acoustic echo canceler includes a first analysis filter bank for dividing a reception signal into a plurality of sub-bands, a plurality of adaptive filters for individually producing false echo signals from the reception signal after divided into the sub-bands, a second analysis filter bank for dividing an input signal into a plurality of sub-bands, a plurality of subtractors for subtracting the false echo signals corresponding to the sub-bands from the input signal after divided into the sub-bands, and a synthesis filter bank for composing outputs of the subtractors. The acoustic echo canceler further includes a band information calculation section for estimating influences of the echoes for the individual sub-bands and determining a priority order based on the estimation. Each of the adaptive filters determines processing to be executed thereby based on the priority order.

Claims

1. An acoustic echo canceler, comprising:

a first analysis filter bank for dividing a reception signal to be converted into an acoustic signal by a loudspeaker into a plurality of sub-bands;

a plurality of adaptive filters for individually producing false echo signals from the reception signal after division of the reception signal into the sub-bands by said first analysis filter bank;

a second analysis filter bank for dividing an input signal from a microphone, which is provided at a position at which said microphone can detect the acoustic signal as echoes, into a plurality of sub-bands same as the first-mentioned sub-bands;

a plurality of subtractors for subtracting the false echo signals corresponding to the sub-bands from the input signal after division of the input signal into the sub-bands by said second analysis filter bank;

a synthesis filter bank for synthesizing outputs of said subtractors; and

a band information calculation section receiving the reception signal and the input signal, estimating influences of the echoes for the individual sub-bands based on the received reception signal and input signal, and determining a priority order based on the estimation;

each of said adaptive filters determining processing to be executed thereby based on the priority order.

2. An acoustic echo canceler as claimed in claim 1, wherein one of said adaptive filters which has a high priority based on the priority order executes processing which is more complicated and has a higher echo suppression effect than another one of said adaptive filters which has a lower priority based on the priority order.

3. An acoustic echo canceler as claimed in claim 1, wherein said band information calculation section receives directly both the reception signal and the input signal, and effects estimation based on the directly-received reception signal and the directly-received input signal.

8. An acoustic echo canceler as claimed in claim 1, wherein said band information calculation section effects estimation based on the input signal after division of the input signal into the sub-bands and the reception signal after division of the reception signal into the sub-bands.

4. An acoustic echo canceler, comprising:

a first analysis filter bank for dividing a reception signal to be converted into an acoustic signal by a loudspeaker into a plurality of sub-bands;

a plurality of adaptive filters for individually producing false echo signals from the reception signal after division into the sub-bands by said first analysis filter bank;

a second analysis filter bank for dividing an input signal from a microphone, which is provided at a position at which said microphone can detect the acoustic signal as echoes, into a plurality of sub-bands same as the first-mentioned sub-bands;

a plurality of subtractors for subtracting the false echo signals corresponding to the sub-bands from the input signal after division into the sub-bands by said second analysis filter bank;

a synthesis filter bank for synthesizing outputs of said subtractors; and

a band information calculation section for estimating influences of the echoes for the individual sub-bands and determining a priority order based on the estimation;

each of said adaptive filters determining processing to be executed thereby based on the priority order;

wherein said band information calculation section includes a first power spectrum calculation section for calculating a power spectrum of the input signal, a second power spectrum calculation section for calculating a power spectrum of the reception signal, a first signal distribution deviation calculation section for calculating a distribution of energy of the input signal for the individual sub-bands based on an output of said first power spectrum calculation section, a second signal distribution deviation calculation section for calculating a distribution of energy of the reception signal for the individual sub-bands based on an output of said second power spectrum calculation section, a plurality of subtractors for calculating differences between the energy of the input signal and the energy of the reception signal for the individual sub-bands, a first priority order determination section for determining a first priority order based on outputs of said subtractors, a second priority order determination section for determining a second priority order based on outputs of said second signal distribution deviation calculation section, and a third priority order determination section for determining a final priority order based on the first priority order and the second priority order.

5. An acoustic echo canceler as claimed in claim 4, wherein said first priority order determination section applies a priority order to the sub-bands in a descending order of the energy of the input signal beginning with one of the sub-bands with which energy of the input signal is higher than energy of the reception signal to determine the first priority order while said second priority order determination section applies a priority order to the sub-bands in a descending order of the energy of the reception signal to determine a second priority order, and said third priority order determination section refers to the first priority order to correct the second priority order to determine a final priority order.

6. An acoustic echo canceler, comprising:

a first analysis filter bank for dividing a reception signal to be converted into an acoustic signal by a loudspeaker into a plurality of sub-bands;

a plurality of adaptive filters for individually producing false echo signals from the reception signal after division into the sub-bands by said first analysis filter bank;

a second analysis filter bank for dividing an input signal from a microphone, which is provided at a position at which said microphone can detect the acoustic signal as echoes, into a plurality of sub-bands same as the first-mentioned sub-bands;

a plurality of subtractors for subtracting the false echo signals corresponding to the sub-bands from the input signal after division into the sub-bands by said second analysis filter bank;

a synthesis filter bank for synthesizing outputs of said subtractors; and

a band information calculation section for estimating influences of the echoes for the individual sub-bands and determining a priority order based on the estimation;

each of said adaptive filters determining processing to be executed thereby based on the priority order,

wherein said band information calculation section includes a subtractor for calculating a difference between the input signal and a second error echo signal different from the first-mentioned error echo signal, an auxiliary adaptive filter for referring to an output of said subtractor to update the filter coefficients and producing the second error echo signal from the reception signal, a discrete Fourier transform section for discrete Fourier transforming the filter coefficients, a plurality of coefficient addition sections for adding outputs of said discrete Fourier transform section for the individual sub-bands, and a priority order determination section for determining a priority order based on outputs of said coefficient addition sections.

7. An acoustic echo canceler as claimed in claim 6, wherein said priority order determination section determines a priority order to the sub-bands in a descending order of the outputs of said coefficient addition sections.

9. An acoustic echo canceler, comprising:

a first analysis filter bank for dividing a reception signal to be converted into an acoustic signal by a loudspeaker into a plurality of sub-bands;

a plurality of adaptive filters for individually producing false echo signals from the reception signal after division into the sub-bands by said first analysis filter bank;

a second analysis filter bank for dividing an input signal from a microphone, which is provided at a position at which said microphone can detect the acoustic signal as echoes, into a plurality of sub-bands same as the first-mentioned sub-bands;

a plurality of subtractors for subtracting the false echo signals corresponding to the sub-bands from the input signal after division into the sub-bands by said second analysis filter bank;

a synthesis filter bank for synthesizing outputs of said subtractors; and

a band information calculation section for estimating influences of the echoes for the individual sub-bands and determining a priority order based on the estimation;

each of said adaptive filters determining processing to be executed thereby based on the priority order,

wherein said band information calculation section includes a plurality of first power calculation sections for individually calculating powers of the input signal after division of the input signal into the sub-bands, a plurality of second power calculation sections for individually calculating powers of the reception signal after division of the reception signal into the sub-bands, a plurality of subtractors for calculating differences between outputs of said first power calculation sections and outputs of said second power calculation sections for the individual sub-bands, a first priority order determination section for determining a first priority order based on outputs of said subtractors, a second priority order determination section for determining a second priority order based on outputs of said power calculation sections, and a third priority order determination section for determining a final priority order based on the first priority order and the second priority order.

10. An acoustic echo canceler as claimed in claim 9, wherein said first priority order determination section applies a priority order to the sub-bands in a descending order of the differences beginning with one of the sub-bands with which the output of the second power calculation section is higher than the output of the first power calculation section to determine the first priority order while said second priority order determination section applies a priority order to the sub-bands in a descending order of the outputs of said second power calculation sections to determine the second priority order, and said third priority order determination section refers to the first priority order to correct the second priority order to determine the final priority order.