Binaural hearing system configured to localize a sound source

Patent metadata

Field	Value
Publication number	US-2018041849-A1
Application number	US-201715669020-A
Country	US
Kind code	A1
Filing date	Aug 4, 2017
Priority date	Aug 5, 2016
Publication date	Feb 8, 2018
Grant date	—

Abstract

A hearing aid system comprising a pair of hearing devices, e.g. hearing aids, worn at the ears of a user receives a target signal generated by a target signal source and transmitted through an acoustic channel to microphones of the hearing aid system. Due to (potential) additive environmental noise, a noisy acoustic signal is received at the microphones of the hearing system. An essentially noise-free version of the target signal is simultaneously transmitted to the hearing devices of the hearing system via a wireless connection. Based on a sound propagation model of the acoustic propagation channel from the target sound source to the microphones of the hearing aid system, and on relative transfer functions representing direction-dependent filtering effects of the head and torso of the user in the form of direction-dependent acoustic transfer functions from a microphone on one side of the head, to a microphone on the other side of the head, a direction-of-arrival (DoA) of the target sound signal relative to the user is determined using a maximum likelihood approach.

First claim

1 . A hearing aid system comprising left and right hearing devices adapted to be worn at left and right ears of a user,
the left hearing device comprising at least one left input transducer (M left ) for converting received sound signal to an electric input signal (r left ), the input sound comprising a mixture of a target sound signal from a target sound source and a possible additive noise sound signal at the location of the at least one left input transducer; the right hearing device comprising at least one right input transducer (M right ) for converting received sound signal to an electric input signal (r right ), the input sound comprising a mixture of a target sound signal from a target sound source and a possible additive noise sound signal at the location of the at least one right input transducer; the hearing aid system further comprising a first transceiver unit configured to receive a wirelessly transmitted version of the target signal and providing an essentially noise-free target signal; a signal processing unit connected to said at least one left input transducer, to said at least one right input transducer, and to said wireless transceiver unit,
the signal processing unit being configured to be used for estimating a direction-of-arrival of the target sound signal relative to the user based on
a signal model for a received sound signal r m at microphone M m (m=left, right) through an acoustic propagation channel from the target sound source to the microphone m when worn by the user;
a maximum likelihood framework;
relative transfer functions representing direction-dependent filtering effects of the head and torso of the user in the form of direction-dependent acoustic transfer functions from a microphone on one side of the head, to a microphone on the other side of the head.

2 . A hearing aid system according to claim 1 configured to provide that the signal processing unit has access to a database of relative transfer functions Ψ ms for different directions (θ) relative to the user.

3 . A hearing aid system according to claim 2 wherein the database of relative transfer functions Ψ ms is stored in a memory of the hearing aid system.

4 . A hearing aid system according to claim 1 wherein the signal model is given by the following expression
r m ( n )= s ( n )* h m ( n , θ)+ v m ( n ), ( m ={left,right} or {1,2}),

where s is the essentially noise-free target signal emitted by the target sound source, h m is the acoustic channel impulse response between the target sound source and microphone m, and v m is an additive noise component, θ is an angle of a direction-of-arrival of the target sound source relative to a reference direction defined by the user and/or by the location of the first and second hearing devices at the ears of the user, n is a discrete time index, and * is the convolution operator.

5 . A hearing aid system according to claim 1 configured to provide that said left and right hearing devices, and said signal processing unit are located in or constituted by three physically separate devices.

6 . A hearing aid system according to claim 1 configured to provide that each of said left and right hearing devices comprise a signal processing unit, and to provide that information signals, e.g. audio signals, or parts thereof, can be exchanged between the left and right hearing devices.

7 . A hearing aid system according to claim 1 comprising a time to time-frequency conversion unit for converting an electric input signal in the time domain into a representation of the electric input signal in the time-frequency domain, providing the electric input signal at each time instance 1 in a number for frequency bins k, k=1, 2, . . . , N.

8 . A hearing aid system according to claim I wherein the signal processing unit is configured to provide a maximum-likelihood estimate of the direction of arrival θ of the target sound signal.

9 . A hearing aid system according to claim I wherein the sound propagation model of an acoustic propagation channel from the target sound source to the hearing device when worn by the user comprises a signal model defined by
R m ( l, k )= S ( l, k ) H m ( k , θ)+( l, k )

where R m (l, k) is a time-frequency representation of the noisy target signal, S(l, k) is a time-frequency representation of the noise-free target signal, H m (k, θ) is a frequency transfer function of the acoustic propagation channel from the target sound source to the respective input transducers of the hearing devices, and V m (l, k) is a time-frequency representation of the additive noise.

10 . A hearing aid system according to claim 1 wherein the signal processing unit is configured to provide a maximum-likelihood estimate of the direction of arrival 0 of the target sound signal by finding the value of θ, for which the log likelihood function is maximum, and wherein the expression for the log likelihood function is adapted to allow a calculation of individual values of the log likelihood function for different values of the direction-of-arrival (θ) using the inverse Fourier transform, e.g. IDFT, such as IFFT.

11 . A hearing aid system according to claim 1 wherein the at least one input transducer of the left hearing devices is equal to one, e.g. a left microphone, and wherein the at least one input transducer of the right hearing devices is equal to one, e.g. a right microphone.

12 . A hearing aid system according to claim 2 wherein the database of relative transfer functions Ψ ms for different directions (θ) relative to the user are frequency dependent.

13 . A hearing aid system according to claim 1 configured to approximate the acoustic transfer function from a target sound source in the front-left quarter plane (−90°-0° to the at least one left input transducer and the acoustic transfer function from a target sound source in the front-right quarter plane (0°-+90°) to at least one right input transducer as a frequency-independent attenuation and a frequency-independent delay.

14 . A hearing aid system according to claim 1 configured to evaluate the log likelihood function L for relative transfer functions Ψ ms corresponding to the directions on the left side of the head (θ∈ [-90°; 0°]), where the acoustic channel parameters of a left input transducer, e.g. a left microphone, are assumed to be frequency independent.

15 . A hearing aid system according to claim 1 configured to evaluate the log likelihood function L for relative transfer functions Ψ ms corresponding to the directions on the right side of the head (θ ∈ [0°; +90°]), where the acoustic channel parameters of a right input transducer, e.g. a right microphone, are assumed to be frequency independent.

16 . A hearing aid system according to claim 1 wherein at least one of the left and right hearing devices comprises a hearing aid, a headset, an earphone, an ear protection device or a combination thereof.

17 . A hearing aid system according to claim 1 comprising an auxiliary device, the hearing aid system being adapted to establish a communication link between the hearing devices and the auxiliary device to provide that information can be exchanged or forwarded from one to the other.

18 . A hearing aid system according to claim 16 comprising a non-transitory application, termed an APP, comprising executable instructions configured to be executed on the auxiliary device to implement a user interface for the hearing aid system.

19 . A method of operating a hearing aid system comprising left and righ

Assignees

• Oticon As

Inventors

• Farmani Mojtaba
• Pedersen Michael Syskind
• Jensen Jesper

Classifications

• H04R25/554

  using a wireless connection, e.g. between microphone and amplifier or using Tcoils · CPC title

• H04R25/552 Primary

  Binaural · CPC title

• H04R25/505

  using digital signal processing · CPC title

• H04R25/407

  Circuits for combining signals of a plurality of transducers · CPC title

• H04R25/405

  by combining a plurality of transducers · CPC title