Method for detection of own voice activity in a communication device

• US 20060262944A1
• Filed: 02/04/2004
• Published: 11/23/2006
• 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: Laugesen, Seren, Rasmussen, Karsten Bo
• Granted Patent: US 7,512,245 B2
• Time in Patent Office: Days
• 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 whereby one or both of the following set of actions are performed,

A:

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

the characteristics, 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 this characteristic it is assessed whether the sound signals originates from the users own voice or originates from another source,

B;

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

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, and based on this characteristic it is assessed whether the sound signals originates from the users own voice or originates from another source.

2. Method as claimed in 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. Method as claimed in claim 1, 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 in the form of FIR filters, the 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 in each hearing aid is compared with the M2R using more than one microphone in each hearing aid in order to take into account the different source strengths pertaining to the different acoustic sources.

5. Method as claimed in 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. Method as claimed in claim 4 wherein M2R is determined in the following way:

$M<br><br>\text{\hspace{1em}<br><br>}<br><br>2<br><br>R<br><br>\left(f\right)=10<br><br>{\log }_{10}<br><br>\left(\frac{{<br><br>Y_{\mathrm{Mo}}<br><br>\left(f\right)<br><br>}^2}{{<br><br>Y_{\mathrm{Rff}}<br><br>\left(f\right)<br><br>}^2}\right),$

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.