Method for detection of own voice activity in a communication device

• US 7,512,245 B2
• Filed: 02/04/2004
• Issued: 03/31/2009
• Est. Priority Date: 02/25/2003
• Status: Active Grant

• Current Assignee: Oticon A/S (William Demant Fonden)
• Original Assignee: Oticon A/S (William Demant Fonden)
• Inventors: Rasmussen, Karsten Bo, Laugesen, Soren
• Primary Examiner(s): Mei; Xu
• Application Number:
  US10/546,919
• Publication Number:
  US 20060262944A1
• Time in Patent Office: 1,882 Days
• Field of Search: 381312-331, 381/91, 381/92, 381/122, 381/95, 381/56, 381/110, 704/272
• US Class Current: 381/110
• CPC Class Codes: G10L 2021/02166 Microphone arrays; Beamforming
• CPC Class Codes: G10L 25/78 Detection of presence or absence of voice signals switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10
• CPC Class Codes: H04R 25/407 Circuits for combining signals of a plurality of transducers
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

In the method according to the invention a signal processing unit receives signals from at least two microphones worn on the user'"'"'s head, which are processed so as to distinguish as well as possible between the sound from the user'"'"'s mouth and sounds originating from other sources. The distinction is based on the specific characteristics of the sound field produced by own voice, e.g. near-field effects (proximity, reactive intensity) or the symmetry of the mouth with respect to the user'"'"'s head.

Claims

1. Method for detection of own voice activity in a communication device,

the method comprising:

providing at least a microphone at each ear of a person and receiving sound signals from the microphones and routing the microphone signals to a signal processing unit wherein the following processing of the signals takes place;

characteristics of a signal, which are due to the fact that the user'"'"'s mouth is placed symmetrically with respect to the user'"'"'s head are determined, and based on these determined characteristics it is assessed whether the sound signals originate from the users own voice or originate from another source.

2. The Method of claim 1, whereby the overall signal level in the microphone signals is determined in the signal processing unit, and this characteristic is used in the assessment of whether the signal is from the users own voice.

3. The Method of claim 1, whereby the characteristics, which are due to the fact that the user'"'"'s mouth is placed symmetrically with respect to the user'"'"'s head are determined by receiving the signals x₁(n) and x₂(n), from microphones positioned at each ear of the user, and compute the cross-correlation function between the two signals:

R_x1x2(k)=E{x₁(n)x₂(n−

k)}, applying a detection criterion to the output R_x1x2(k), such that if the maximum value of R_x1x2(k) is found at k=0 the dominating sound source is in the median plane of the user'"'"'s head whereas if the maximum value of R_x1x2(k) is found elsewhere the dominating sound source is away from the median plane of the user'"'"'s head.

4. A Method for detection of own voice activity in a communication device, the method comprising:

providing at least two microphones at an ear of a person;

receiving sound signals from the microphones;

routing the signals to a signal processing unit; and

processing of the routed signals, wherein processing comprises determining characteristics of a signal based on the fact that the microphones are in the acoustical near-field of the speaker'"'"'s mouth and in the far-field of the other sources of sound, and assessing, based on these determined characteristics, whether the sound signals originate from the users own voice or originate from another source;

whereby the characteristics, which are due to the fact that the microphones are in the acoustical near-field of the speaker'"'"'s mouth are determined by a filtering process comprising FIR filters, filter coefficients of which are determined so as to maximize the difference in sensitivity towards sound coming from the mouth as opposed to sound coming from all directions by using a Mouth-to-Random-far-field index (abbreviated M2R) whereby the M2R obtained using only one microphone at an ear is compared with the M2R using more than one microphone at said ear in order to take into account the different source strengths pertaining to the different acoustic sources; and

wherein M2R is determined by the expression;

$M<br><br><br><br>2<br><br>R<br><br>\left(f\right)=10<br><br>{\log }_{10}<br><br>\left(\frac{{<br><br>Y_{\mathrm{Mo}}<br><br>\left(f\right)<br><br>}^2}{{<br><br>Y_{\mathrm{Rff}}<br><br>\left(f\right)<br><br>}^2}\right),$

where Y_Mo(f) is the spectrum of the output signal y(n) due to the mouth alone, Y_Rff(f) is the spectrum of the output signal y(n) averaged across a representative set of far-field sources and f denotes frequency.

5. An apparatus for detection of own voice activity in a communication device comprising:

at least three microphones, wherein at least two of said microphones are configured to be disposed at an ear of a person and further wherein at least one of said microphones is configured to be disposed at the other ear of said person;

a microphone input routing device that routs sound signals received by said microphones to a signal processing unit; and

a signal processing unit that processes the routed sound signals, wherein the signal processing unit comprises;

an acoustical near-field determination unit that determines first characteristics based on the routed sound signals related to the location of said at least two microphones in the acoustical near-field of said person'"'"'s mouth and in the acoustical far-field of other sources of sound;

a mouth position symmetry analysis unit that determines second characteristics based on the routed sound signals related to the fact that said person'"'"'s mouth is located symmetrically with respect to said person'"'"'s head; and

a characteristics assessment unit that assesses, based on said first and second characteristics, whether said sound signals originate from said person'"'"'s own voice or from another source.

6. The apparatus of claim 5 whereby the acoustical near-field determination unit determines characteristics by a filtering process comprising FIR filters, filter coefficients of which are determined so as to maximize the difference in sensitivity towards sound coming from the mouth as opposed to sound coming from all directions by using a Mouth-to-Random-far-field index (abbreviated M2R) whereby the M2R obtained using only one microphone at an ear is compared with the M2R using more than one microphone at said ear in order to take into account the different source strengths pertaining to the different acoustic sources.

7. The apparatus of claim 5 wherein the acoustical near-field determination unit employs an M2R is determined by the expression:

$M<br><br><br><br>2<br><br><br><br>R<br><br>\left(f\right)=10<br><br><br><br>{\log }_{10}<br><br>\left(\frac{{<br><br>Y_{\mathrm{Mo}}<br><br>\left(f\right)<br><br>}^2}{{<br><br>Y_{\mathrm{Rff}}<br><br>\left(f\right)<br><br>}^2}\right),$

where Y_Mo(f) is the spectrum of the output signal y(n) due to the mouth alone, Y_Rff(f) is the spectrum of the output signal y(n) averaged across a representative set of far-field sources and f denotes frequency.

8. An apparatus for detection of own voice activity in a communication device comprising:

at least two microphones, wherein one of said at least two microphones is configured to be disposed at an ear of a person and another of said at least two microphones is configured to be disposed at the other ear of a person;

a microphone input routing device that routs sound signals received by said microphones to a signal processing unit; and

a signal processing unit that processes the routed sound signals, wherein the signal processing unit comprises;

a mouth position symmetry analysis unit that determines characteristics based on the routed sound signals related to the fact that said person'"'"'s mouth is located symmetrically with respect to said person'"'"'s head; and

a characteristics assessment unit that assesses, based on said characteristics, whether said sound signals originate from said person'"'"'s own voice or from another source.

9. The apparatus of claim 8, whereby the mouth position symmetry analysis unit determines characteristics by receiving the signals x₁(n) and x₂(n), from the microphones positioned at each ear of the user, and computing the cross-correlation function between the two signals:

R_x1x2(k)=E{x₁(n)x₂(n−

k)}, applying a detection criterion to the output R_x1x2(k), such that if the maximum value of R_x1x2(k) is found at k=0 the dominating sound source is in the median plane of the user'"'"'s head whereas if the maximum value of R_x1x2(k) is found elsewhere the dominating sound source is away from the median plane of the user'"'"'s head.

10. The apparatus of claim 8, whereby the overall signal level in the microphone signals is determined in the signal processing unit, and this characteristic is used in the assessment of whether the signal is from the users own voice.

11. An apparatus for detection of own voice activity in a communication device comprising:

at least two microphones, wherein at least two of said microphones are configured to be disposed at an ear of a person;

a microphone input routing device that routs sound signals received by said microphones to a signal processing unit; and

a signal processing unit that processes the routed sound signals, wherein the signal processing unit comprises;

an acoustical near-field determination unit that determines characteristics based on the routed sound signals related to the location of said microphones in the acoustical near-field of said person'"'"'s mouth and in the acoustical far-field of other sources of sound;

a characteristics assessment unit that assesses, based on said characteristics, whether said sound signals originate from said person'"'"'s own voice or from another source;

whereby the acoustical near-field determination unit determines characteristics by a filtering process comprising FIR filters, filter coefficients of which are determined so as to maximize the difference in sensitivity towards sound coming from the mouth as opposed to sound coming from all directions by using a Mouth-to-Random-far-field index (abbreviated M2R) whereby the M2R obtained using only one microphone at an ear is compared with the M2R using more than one microphone at said ear in order to take into account the different source strengths pertaining to the different acoustic sources; and

wherein the acoustical near-field determination unit employs an M2R is determined by the expression;

$M<br><br><br><br>2<br><br><br><br>R<br><br>\left(f\right)=10<br><br><br><br>{\log }_{10}<br><br>\left(\frac{{<br><br>Y_{\mathrm{Mo}}<br><br>\left(f\right)<br><br>}^2}{{<br><br>Y_{\mathrm{Rff}}<br><br>\left(f\right)<br><br>}^2}\right),$

where Y_Mo(f) is the spectrum of the output signal y(n) due to the mouth alone, Y_Rff(f) is the spectrum of the output signal y(n) averaged across a representative set of far-field sources and f denotes frequency.

12. The apparatus of claim 11, whereby the overall signal level in the microphone signals is determined in the signal processing unit, and this characteristic is used in the assessment of whether the signal is from the users own voice.

13. Method for detection of own voice activity in a communication device whereby both of the following sets of actions are performed,

A:

providing at least two microphones at an ear of a person, receiving sound signals from the microphones and routing the signals to a signal processing unit wherein the following processing of the signal takes place;

characteristics of a signal, which are due to the fact that the microphones are in the acoustical near-field of the speaker'"'"'s mouth and in the far-field of the other sources of sound are determined, and based on these determined characteristics it is assessed whether the sound signals originate from the users own voice or originate from another source,

B;

providing at least a microphone at each ear of a person and receiving sound signals from the microphones and routing the microphone signals to a signal processing unit wherein the following processing of the signals takes place;

characteristics of a signal, which are due to the fact that the user'"'"'s mouth is placed symmetrically with respect to the user'"'"'s head are determined, and based on these determined characteristics it is assessed whether the sound signals originate from the users own voice or originate from another source.

14. The Method of claim 13 whereby the characteristics, which are due to the fact that the microphones are in the acoustical near-field of the speaker'"'"'s mouth are determined by a filtering process comprising FIR filters, filter coefficients of which are determined so as to maximize the difference in sensitivity towards sound coming from the mouth as opposed to sound coming from all directions by using a Mouth-to-Random-far-field index (abbreviated M2R) whereby the M2R obtained using only one microphone at an ear is compared with the M2R using more than one microphone at said ear in order to take into account the different source strengths pertaining to the different acoustic sources.

15. The method of claim 14, wherein M2R is determined by the expression:

$M<br><br><br><br>2<br><br><br><br>R<br><br>\left(f\right)=10<br><br><br><br>{\log }_{10}<br><br>\left(\frac{{<br><br>Y_{\mathrm{Mo}}<br><br>\left(f\right)<br><br>}^2}{{<br><br>Y_{\mathrm{Rff}}<br><br>\left(f\right)<br><br>}^2}\right),$

where Y_Mo(f) is the spectrum of the output signal y(n) due to the mouth alone, Y_Rff(f) is the spectrum of the output signal y(n) averaged across a representative set of far-field sources and f denotes frequency.