Hearing aid configured to select a reference microphone

Abstract

A hearing aid includes at least two microphones, providing respective at least two electric input signals representing sound around the user; a filter bank converting the electric input signals into signals as a function of time and frequency; a directional system connected to the microphones and being configured to provide a filtered signal in dependence of the electric input signals and fixed or adaptively updated beamformer weights. At least one direction to a target sound source is defined as a target direction. For each frequency band, one of the microphones is selected as a reference microphone, thereby providing a reference input signal for each frequency band. The reference microphone may be selected in dependence of directional data related to directional characteristics of the microphones. The reference microphone may be different for at least two frequency bands. The reference microphone may be adaptively selected based on a logic criterion.

Claims

1. A hearing aid adapted for being worn by a user at or in an ear of the user or to be partially or fully implanted in the user's head at an ear of the user, the hearing aid comprising at least two microphones, providing respective at least two electric input signals representing sound around the user wearing the hearing aid; a filter bank converting the at least two electric input signals into signals as a function of time and frequency; a directional system connected to said at least two microphones and being configured to provide a filtered signal in dependence of said at least two electric input signals and fixed or adaptively updated beamformer weights; and a direction to a target sound source being defined as a target direction; wherein for each frequency band, one of said at least two microphones at a given point in time is selected as a reference microphone, thereby providing a reference input signal for each frequency band, wherein the reference microphone for a given frequency band is selected in dependence of directional data related to directional characteristics of said at least two microphones, at the given point in time, for target sound impinging on the hearing aid from the target direction at said given point in time.

2. A hearing aid according to claim 1 wherein the reference microphone for a given frequency band is adaptively selected.

3. A hearing aid according to claim 2 wherein the reference microphone for a given frequency band is adaptively selected based on a logic criterion.

4. A hearing aid according to claim 1 comprising a memory, or circuitry for establishing a communication link to a database, comprising directional data related to directional characteristics of said at least two microphones; and wherein the reference microphone for a given frequency band is adaptively selected based on said directional data.

5. A hearing aid according to claim 1 wherein said directional data comprise a directivity index or a front-back ratio.

6. A hearing aid according to claim 5 wherein the reference microphone for a given frequency band is selected as the microphone exhibiting maximum directivity index or maximum front-back-ratio, at the given point in time, for target sound impinging on the hearing aid from the target direction at said given point in time.

7. A hearing aid according to claim 1 wherein the directional system is implemented as or comprise a minimum variance distortionless response (MVDR) beamformer depending on the selected reference microphone.

8. A hearing aid according to claim 1 wherein said target direction is provided via a user interface.

9. A hearing aid according to claim 1 configured to estimate the target direction.

10. A hearing aid according to claim 1 comprising a voice activity detector for estimating whether or not, or with what probability, an input signal comprises a voice signal at a given point in time.

11. A hearing aid according to claim 1 being constituted by or comprising an air-conduction type hearing aid, a bone-conduction type hearing aid, a cochlear implant type hearing aid, or a combination thereof.

12. A binaural hearing aid system comprising a first hearing aid and a second hearing aid according to claim 1, wherein said first and second hearing aids are configured as a binaural hearing aid system allowing data to be exchanged between the first and second hearing aids.

13. A binaural hearing aid system according to claim 12 wherein the reference microphone is selected in dependence of the intended application of the filtered signal.

14. A binaural hearing aid system according to claim 12 wherein the reference microphone is selected independently in the first and second hearing aids.

15. A hearing aid according to claim 1, wherein the at least two electric input signals are converted by the filter bank into signals represented by complex-valued time-frequency units.

16. A hearing aid system adapted for being worn by a user, the hearing aid system comprising a hearing aid and at least one further device, the hearing aid system further comprising at least two microphones, providing respective at least two electric input signals representing sound around the user wearing the hearing aid system; a filter bank converting the at least two electric input signals into signals as a function of time and frequency; a directional system connected to said at least two microphones and being configured to provide a filtered signal in dependence of said at least two electric input signals and fixed or adaptively updated beamformer weights; and transceiver circuitry for establishing a communication link allowing data to be exchanged between the hearing aid and the at least one further device, wherein the hearing aid system is configured to provide that at least one direction to a target sound source is defined as a target direction, for each frequency band, one of said at least two microphones at a given point in time is selected as a reference microphone, thereby providing a reference input signal for each frequency band, wherein the reference microphone for a given frequency band is selected in dependence of directional data related to directional characteristics of said at least two microphones, at the given point in time, for target sound impinging on the hearing aid from the target direction at said given point in time.

17. A hearing aid system according to claim 16 wherein said hearing aid comprises a first hearing aid and wherein said at least one further device comprises a second hearing aid, and wherein each of the first and second hearing aids comprises at least one of said at least two microphones.

18. A hearing aid system according to claim 16 wherein said at least one further device comprises, or is configured to exchange data with, an auxiliary device comprising a user interface for the hearing aid system.

19. A hearing aid system according to claim 16 wherein said directional data comprise a directivity index or a front-back ratio.

20. A method of operating a hearing aid adapted for being worn by a user at or in an ear of the user or to be partially or fully implanted in the user's head at an ear of the user, the hearing aid comprising at least two microphones, the method comprising providing by said at least two microphones at least two electric input signals representing sound around the user wearing the hearing aid; converting the at least two electric input signals into signals as a function of time and frequency; providing a filtered signal in dependence of said at least two electric input signals and fixed or adaptively updated beamformer weights; and defining at least one direction to a target sound source as a target direction, for each frequency band, selecting one of said at least two microphones at a given point in time as a reference microphone, thereby providing a reference input signal for each frequency band, wherein the reference microphone for a given frequency band is selected in dependence of directional data related to directional characteristics of said at least two microphones, at the given point in time, for target sound impinging on the hearing aid from the target direction at said given point in time.

21. A method according to claim 20 wherein said directional data comprise a directivity index or a front-back ratio.

22. A hearing aid adapted for being worn by a user at or in an ear of the user or to be partially or fully implanted in the user's head at an ear of the user, the hearing aid comprising at least two microphones, providing respective at least two electric input signals representing sound around the user wearing the hearing aid; a filter bank converting the at least two electric input signals into signals as a function of time and frequency; a directional system connected to said at least two microphones and being configured to provide a filtered signal in dependence of said at least two electric input signals and fixed or adaptively updated beamformer weights; and a direction to a target sound source being defined as a target direction; wherein for each frequency band, one of said at least two microphones at a given point in time is selected as a reference microphone, thereby providing a reference input signal for each frequency band, wherein the reference microphone for a given frequency band is selected as the microphone exhibiting maximum directivity index or maximum front-back-ratio, at the given point in time, for target sound impinging on the hearing aid from the target direction at said given point in time.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The aspects of the disclosure may be best understood from the following detailed description taken in conjunction with the accompanying figures. The figures are schematic and simplified for clarity, and they just show details to improve the understanding of the claims, while other details are left out. Throughout, the same reference numerals are used for identical or corresponding parts. The individual features of each aspect may each be combined with any or all features of the other aspects. These and other aspects, features and/or technical effect will be apparent from and elucidated with reference to the illustrations described hereinafter in which:

(2) FIG. 1A shows a typical location of microphones in a behind the ear (BTE) hearing instrument, and

(3) FIG. 1B shows a typical location of microphones in an in-the-ear (ITE) hearing instrument,

(4) FIGS. 2A, 2B and 2C schematically illustrates the difference between the front microphone directivity index and the rear microphone directivity index for three, respectively, different target directions,

(5) FIGS. 3A, 3B and 3C schematically illustrates the selection of the reference microphone based on the highest directivity index for three, respectively, different target directions,

(6) FIG. 4 shows a block diagram of an embodiment of a hearing aid according to the present disclosure,

(7) FIG. 5 shows an embodiment of a hearing aid according to the present disclosure comprising a BTE-part located behind an ear or a user and an ITE part located in an ear canal of the user in communication with an auxiliary device comprising a user interface for the hearing aid, and

(8) FIG. 6 shows an embodiment of a binaural hearing aid system according to the present disclosure.

(9) The figures are schematic and simplified for clarity, and they just show details which are essential to the understanding of the disclosure, while other details are left out. Throughout, the same reference signs are used for identical or corresponding parts.

(10) Further scope of applicability of the present disclosure will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by way of illustration only. Other embodiments may become apparent to those skilled in the art from the following detailed description.

(11) Embodiments of the disclosure may e.g. be useful in applications such as hearing aids or headsets.

DETAILED DESCRIPTION OF EMBODIMENTS

(12) The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. Several aspects of the apparatus and methods are described by various blocks, functional units, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements”). Depending upon particular application, design constraints or other reasons, these elements may be implemented using electronic hardware, computer program, or any combination thereof.

(13) The electronic hardware may include micro-electronic-mechanical systems (MEMS), integrated circuits (e.g. application specific), microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), gated logic, discrete hardware circuits, printed circuit boards (PCB) (e.g. flexible PCBs), and other suitable hardware configured to perform the various functionality described throughout this disclosure, e.g. sensors, e.g. for sensing and/or registering physical properties of the environment, the device, the user, etc. Computer program shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

(14) The present application relates to the field of hearing aids, specifically to a hearing aid comprising a multitude (e.g. ≥2) of input transducers (e.g. microphones) and a directional system for providing a spatially filtered (beamformed) signal based on signals from the input transducers. In directionality, the noise is typically attenuated by use of beamforming. In MVDR (Minimum Variance Distortion-less Response) beamforming, e.g., the microphone signals are processed such that the sound impinging from a target direction at a chosen reference microphone is unaltered. A hearing instrument with directional noise reduction typically contains two or more microphones. The microphone location of different two-microphone instruments is illustrated in FIG. 1A, 1B.

(15) FIG. 1A shows a typical location of microphones in a behind the ear (BTE) hearing instrument (HD), and FIG. 1B shows a typical location of microphones in an in-the-ear (ITE) hearing instrument (HD). In both cases a user (User) wears the hearing instrument (HD) at an ear (Ear), e.g. behind pinna, or at or in the ear canal, respectively.

(16) The hearing aid microphones (M1, M2) are all located near the ear canal. E.g. behind the ear (FIG. 1A) or at the entrance to the ear canal (FIG. 1B) (or a combination thereof). In order to maintain the user's spatial localisation cues (such as interaural time and level differences between the ears, or even pinna-related localization cues), it is desirable to place the microphones close to the user's ear canal.

(17) The microphones (M1, M2) are located in the hearing instrument so that M1 is closest to the front of the user and M2 is closest to the rear of the user. Hence, M1 is referred to as the front microphone and M2 is referred to as the rear microphone.

(18) Due to the location near the head and pinna, the different microphones may have different directional characteristics. A directional characteristic can e.g. be measured in terms of the directivity index or front-back ratio or any other ratio between (signal content in) target direction and non-target directions.

(19) The directivity index DI is given as the ratio between the response of the target direction θ.sub.0 and the response of all other directions:

(20) $\mathrm{DI}\left(k\right)={\log }_{10}\frac{{.Math.R\left({\theta }_0,k\right).Math.}^2}{\int {.Math.R\left(\theta ,k\right).Math.}^{2}d\theta }$

(21) The front-back ratio FBR is the ratio between the responses of the front half plane and the responses of the back half plane:

(22) $\mathrm{FBR}\left(k\right)={\log }_{10}\frac{{\int }_{f\mathrm{ront}}{.Math.R\left(\theta ,k\right).Math.}^{2}d\theta }{{\int }_{back}{.Math.R\left(\theta ,k\right).Math.}^{2}d\theta }$

(23) Other ratios than the front-back ratio may alternatively be used, e.g. a ratio between the magnitude response (e.g. power density) in a smaller angle range (<180°) in the target direction, and the magnitude response in a larger angle range (>180°, remaining) in non-target directions (or vice versa). The directivity index or the front-back ratio may be estimated for different types of isotropic noise fields such as a spherically isotropic noise field (noise equally likely from all directions) or a cylindrically isotropic noise field (noise field is equally likely in the horizontal plane). Typically, an isotropic noise field is only isotropic in absence of the head. An isotropic noise field may be altered by the head and the pinna such that the energy distribution no longer is the same across the uniformly sampled directions.

(24) An example of the (frequency dependent) difference between the directivity index of the front microphone (M1) and the directivity index for the rear microphone (M2) for three different directions to a target sound source is shown in FIGS. 2A, 2B and 2C, respectively. Due to the placement of the microphones, e.g. behind the ear or near the ear canal, the directivity of the microphones is not the same. The location of the front and rear microphones relative to an orientation of the user's head (e.g. nose) is shown in the insert in the top right part of FIG. 2A. Due to the placement of the microphones, e.g. behind the ear or near the ear canal, the directivity of the microphones is not the same. The direction to the target sound source relative to the user is indicated in the small insert with a head and an arrow to the left of the three graphs in FIGS. 2A, 2B and 2C. The target sound source is in front-half plane, directly in front of the user in FIG. 2A (+90°). The target sound source is in front half-plane, to the left of the user in FIG. 2B (˜+135°). The target sound source is in rear half-plane, directly to the rear of the user in FIG. 2C (+270°).

(25) It is clear from FIG. 2A, 2B, 2C that the microphone having the highest directivity depends on both the target direction as well as the frequency. It may thus be advantageous to select the reference microphone depending on the directivity characteristics of the microphones.

(26) For the target impinging from the front, the front microphone (M1) typically has higher directivity, whereas the rear microphone (M2) typically has higher directivity when the target talker is behind the listener. We also notice that the microphone having the highest directivity changes across frequency.

(27) As an alternative to using the directivity index, the transfer function between the microphones may be considered. For a given frequency band k, the reference microphone may be selected based on the microphone which picks up most energy form the target direction.

(28) Normalized relative transfer functions d.sub.m(k) for propagation of sound from a given location to the M microphones (m=1, . . . , M) of the hearing aid (or hearing aid system) can be written in a vector d=[d.sub.1, d.sub.2, . . . , d.sub.M] (sometimes termed ‘steering vector’ or look vector), in which the transfer function of the reference microphone (index m=‘ref’) has the value d.sub.ref=1, and all other elements of d (m≠‘ref’) has a magnitude smaller than one.

(29) This may be an advantage in situations where the relative transfer function from the target direction (or the target directions) may be estimated adaptively during use.

(30) The present disclosure proposes a method to select a reference microphone (or reference signal), where the selection of reference microphone (or reference signal) may vary across the target direction(s) and frequency bands.

(31) The hearing aid may contain at least two microphones a filter bank converting the microphone signals into signals as function of time and frequency, e.g. complex-valued time-frequency units. a directional system with a selected reference microphone for each frequency band. access to data on the hearing instrument microphone's directional data. a direction or a set of directions defined as target direction wherein the reference microphone for a given frequency band is selected based on the microphone's directional data

(32) In an embodiment the selected reference microphone is adaptive depending on an estimated target direction.

(33) In an embodiment the selected reference microphone in a frequency band is the microphone having the highest directivity index for a given target direction or the highest ratio between the selected target directions and the selected noise directions.

(34) In an embodiment the directional system is implemented as an MVDR beamformer.

(35) FIG. 3A, 3B, 3C shows a selection of the reference microphone based on the highest directivity index for three different target directions (same as in FIG. 2A, 2B, 2C). The bold line indicates the front microphone as the selected reference microphone; the dashed line indicates the rear microphone as selected reference microphone. In the schematic illustration of FIG. 3A, 3B, 3C, the reference microphone for a given frequency band and a given direction to the target sound source is chosen to be the microphone having the largest directivity index.

(36) FIG. 4 shows a block diagram of an embodiment of a hearing aid according to the present disclosure. The hearing aid (HD) comprises an exemplary two-microphone beamformer configuration (BF) according to the present disclosure. The hearing aid comprises first and second microphones (M.sub.1, M.sub.2) for converting an input sound (Sound) to first IN.sub.1 and second IN.sub.2 electric input signals, respectively. A front direction is e.g. defined by the microphone axis of the hearing aid when mounted on the user, as indicated in FIG. 4 by arrow denoted ‘Front’ coinciding with the microphone axis. The direction from the target signal (S, Target sound) to the hearing aid microphones (M.sub.1, M.sub.2) is indicated by dotted arrows denoted h.sub.1 and h.sub.2, respectively. The first and second microphones (when located at an ear of the user) are characterized by time-domain impulse responses h.sub.1 (h.sub.1(θ, φ, r)) and h.sub.2 (h.sub.2(θ, φ, r)), respectively (or transfer functions H.sub.1(θ, φ, r, k) and H.sub.2(θ, φ, r, k), respectively, in the frequency domain) The impulse responses (h.sub.1, h.sub.2) (or transfer functions (H.sub.1, H.sub.2)) are representative of acoustic properties of respective ‘propagation channels’ of sound from (target) sound source S located at (θ, φ, r) around the hearing aid to the first and second microphones (M.sub.1, M.sub.2) of the hearing aid (when mounted on the user). The embodiment of a hearing aid of FIG. 4 is configured to operate in the time-frequency domain. The hearing aid hence comprises first and second analysis filter bank units (FBA1 and FBA2) configured to convert the first and second time domain signals IN.sub.1 and IN.sub.2 to time-frequency domain signals IN.sub.m(k), m=1, 2, and k=1, . . . , K, where K is the number of frequency bands (and where the time index is omitted for simplicity). The number M of input transducers (e.g. microphones) may be larger than two.

(37) The hearing aid (HD) further comprises a directional system (beamformer filter) (BF) for providing a beamformed signal Y(k) as a weighted combination of the first and second electric input signals IN1, IN2 using (generally complex) filter coefficients (also denoted beamformer weights) W.sub.1(k) and W.sub.2(k): Y(k)=W.sub.1(k)IN.sub.1(k)+W.sub.2(k)IN.sub.2(k), k=1, . . . , K. In FIG. 4, the filter coefficients W.sub.1(k) and W.sub.2(k) are applied to the input signals IN.sub.1(k) and IN.sub.2(k), respectively, in respective multiplication units (‘x’), k=1, . . . , K. Addition of terms (W.sub.1(k)IN.sub.1(k) and W.sub.2(k)IN.sub.2(k)) having same frequency index is performed in respective summation units (‘+’), k=1, . . . , K. The outputs of the K summation units provide the sub-band signals Y(k), k=1, . . . , K of the beamformed signal. The number K of frequency bands may e.g. be larger than one, e.g. in the range from 4 to 128.

(38) The hearing aid (e.g. as here the directional system) comprises memory (MEM) comprising values of parameters which are relevant for controlling the directional system. At least some of the parameters may be predefined and stored prior to use of the hearing aid. At least some of the parameters may be updated and stored during use of the hearing aid. Directivity characteristics of the first and second microphones for different directions to the target sound source (cf. e.g. FIG. 2A, 2B, 2C) may be stored in the memory. The hearing aid (e.g. as here the directional system) may comprise a reference signal-and-beamformer weight-calculation unit (REF.fwdarw.WGT-CALC) for providing the beamformer weights (W.sub.1(k) and W.sub.2(k), k=1, . . . , K) in dependence of the directivity characteristics of the first and second microphones (M.sub.1, M.sub.2). The memory unit (MEM) may contain directivity characteristics of the first and second microphones for different directions (TD) to the target sound source (e.g. for each frequency band k=1, 2, . . . , K), cf. e.g. signal DIRC(k,TD) between the memory (MEM) and the REF.fwdarw.WGT-CALC-block. The directivity characteristics may e.g. comprise a directivity index (DI) or a front-back ratio (FBR) or similar parameter that can be determined as a frequency dependent indicator of directivity properties of a given microphone configuration. The reference signal for a given direction to the target sound source for a given frequency band k may be extracted from the directivity characteristics, e.g. based on predefined threshold values. The memory may include a reference-indicator REF(k,TD) for each direction (TD) to the target sound source for which directivity properties are stored, and for each frequency band (k). The reference indicator for the given target direction (TD) and frequency band (k) specify whether or not (or with what probability) a given microphone signal is the reference signal. Given the target direction (TD), the REF.fwdarw.WGT-CALC-block may read the corresponding DIRC(k,TD)-values or simply the reference-indicator REF(k,TD) for the given target direction from the memory (MEM).

(39) Filter coefficients W.sub.1(k) and W.sub.2(k), k=1, . . . , K, for different directions to the target signal may be adaptively determined in dependence of first and second electric input signals (IN.sub.1(k), IN.sub.2(k)), the target direction (θ) and the reference-indicator REF(k,θ) for the target direction (θ). The target direction (θ) at a given point in time may e.g. be provided via a user-interface (UI), cf. signal TD (shown by dashed arrow) from the user interface to the reference signal-and-beamformer weight-calculation unit (REF.fwdarw.WGT-CALC). The target direction at a given point in time may e.g. be adaptively estimated, e.g. in the reference signal-and-beamformer weight-calculation unit (REF.fwdarw.WGT-CALC), based on the first and second electric input signals (IN.sub.1(k), IN.sub.2(k)) and signal statistics extracted therefrom (e.g. covariance matrices, acoustic transfer functions, etc., e.g. using a voice activity detector to classify a current acoustic environment to be able to estimate noise properties and speech properties of the current input signals), cf. e.g. EP2701145A1 or [Brandstein & Ward; 2001].

(40) The weights may be calculated similarly to how the weights usually are found. E.g. for an MVDR beamformer

(41) $W_{\mathrm{mvdr}}\left(k\right)=\frac{{\hat{R}}_v^{-1}\left(k\right)\hat{d}\left(k\right)}{{\hat{d}}^H\left(k\right){\hat{R}}_v^{-1}\left(k\right)\hat{d}\left(k\right)}$

(42) Where {circumflex over (R)}.sub.v is an estimate of the inter-microphone noise co-variance matrix R.sub.v and {circumflex over (d)} is an estimate of the steering (or look) vector d for frequency band k. But the size of the weights will be dependent on how the relative transfer function d is scaled. It may, e.g., be an advantage if d is scaled such that its maximum magnitude value is 1, e.g. so that it is the maximum value of the individual components of d, e.g. d=[1,z].sup.T or d=[z,1].sup.T (for a 2-microphone configuration), where |z|<1. Hereby, the weights w become smaller, and the white noise gain (microphone noise) thus becomes smaller.

(43) The beamformer weights may of course be optimized using other optimization criteria than those of the MVDR beamformer. E.g. the criteria of the more general linearly constrained minimum variance (LCMV) beamformer.

(44) Another advantage is fading towards a reference microphone signal (for a given frequency band k, k=1, . . . , K) can be provided, in case noise reduction is not needed. A possible type of fading may be
w.sub.applied(k)=α*w.sub.mvdr(k)+(1−α)*w.sub.ref(k), where

(45) w.sub.applied(k) is the weight vector applied to the microphones, w.sub.mvdr(k) is the weight vector estimated in order to apply maximum noise reduction, w.sub.ref(k) is a vector containing zeros at all indices apart from the reference microphone (which has the value 1) and α is a value between 0 (resulting in the reference microphone signal) and 1 (resulting in maximum noise reduction). The fading weight a may be constant over frequency. It may, however, also be frequency dependent (α(k)).

(46) The hearing aid of FIG. 4 comprises a 2-microphone beamformer configuration comprising a signal processor (SPU) for (further) processing the beamformed signal Y(k) in a number (K) of frequency bands and providing a processed signal OU(k), k=1, 2, . . . , K. The signal processor may be e.g. be configured to apply one or more processing algorithms to a signal of the forward path, e.g. to apply a level and frequency dependent shaping of the beamformed signal, e g to compensate for a user's hearing impairment. The processed frequency band signals OU(k) are fed to a synthesis filter bank FBS for converting the frequency band signals OU(k) to a single time-domain processed (output) signal OUT, which is fed to an output unit for presentation to a user as a signal perceivable as sound. In the embodiment of FIG. 4, the output unit comprises a loudspeaker (SPK) for presenting the processed signal (OUT) to the user as sound (e.g. air borne vibrations). The forward path from the microphones (M.sub.BTE1, M.sub.BTE2) to the loudspeaker (SPK) of the hearing aid is (mainly) operated in the time-frequency domain (in K frequency bands).

(47) FIG. 5 shows an embodiment of a hearing aid according to the present disclosure comprising a BTE-part located behind an ear or a user and an ITE part located in an ear canal of the user in communication with an auxiliary device comprising a user interface for the hearing aid.

(48) FIG. 5 shows an embodiment of a hearing device (HD), e.g. a hearing aid, according to the present disclosure comprising a BTE-part located behind an ear or a user and an ITE part located in an ear canal of the user in communication with an auxiliary device (AUX) comprising a user interface (UI) for the hearing device. FIG. 5 illustrates an exemplary hearing aid (HD) formed as a receiver in the ear (RITE) type hearing aid comprising a BTE-part (BTE) adapted for being located at or behind pinna and a part (ITE) comprising an output transducer (e.g. a loudspeaker/receiver) adapted for being located in an ear canal (Ear canal) of the user (e.g. exemplifying a hearing aid (HD) as shown in FIG. 4). The BTE-part (BTE) and the ITE-part (ITE) are connected (e.g. electrically connected) by a connecting element (IC). In the embodiment of a hearing aid of FIG. 5, the BTE part (BTE) comprises two input transducers (here microphones) (M.sub.1, M.sub.2) each for providing an electric input audio signal representative of an input sound signal from the environment (in the scenario of FIG. 5, including sound source S). The hearing aid of FIG. 5 further comprises two wireless receivers or transceivers (WLR.sub.1, WLR.sub.2) for providing respective directly received auxiliary audio and/or information/control signals (and optionally for transmitting such signals to other devices). The hearing aid (HD) comprises a substrate (SUB) whereon a number of electronic components are mounted, functionally partitioned according to the application in question (analogue, digital, passive components, etc.), but including a signal processor (DSP), a front-end chip (FE), and a memory unit (MEM) coupled to each other and to input and output units via electrical conductors Wx. The mentioned functional units (as well as other components) may be partitioned in circuits and components according to the application in question (e.g. with a view to size, power consumption, analogue vs digital processing, radio communication, etc.), e.g. integrated in one or more integrated circuits, or as a combination of one or more integrated circuits and one or more separate electronic components (e.g. inductor, capacitor, etc.). The signal processor (DSP) provides an enhanced audio signal (cf. signal OUT in FIG. 4), which is intended to be presented to a user. In the embodiment of a hearing aid device in FIG. 5, the ITE part (ITE) comprises an output unit in the form of a loudspeaker (receiver) (SPK) for converting the electric signal (OUT) to an acoustic signal (providing, or contributing to, acoustic signal S.sub.ED at the ear drum (Ear drum). The ITE-part may further comprise an input unit comprising one or more input transducer (e.g. a microphone) (M.sub.ITE) for providing an electric input audio signal representative of an input sound signal from the environment at or in the ear canal. In another embodiment, the hearing aid may comprise only the BTE-microphones (M.sub.1, M.sub.2). In yet another embodiment, the hearing aid may comprise an input unit (e.g. a microphone or a vibration sensor) located elsewhere than at the entrance of the ear canal (e.g. facing the eardrum) in combination with one or more input units located in the BTE-part and/or the ITE-part. The ITE-part further comprises a guiding element, e.g. a dome, (DO) for guiding and positioning the ITE-part in the ear canal of the user.

(49) The hearing aid (HD) exemplified in FIG. 5 is a portable device and further comprises a battery (BAT) for energizing electronic components of the BTE- and ITE-parts.

(50) The hearing aid (HD) comprises a directional microphone system (beamformer filter (BF in FIG. 4)) adapted to enhance a target acoustic source among a multitude of acoustic sources in the local environment of the user wearing the hearing aid device. The memory unit (MEM) may comprise predefined (or adaptively determined) complex, frequency dependent constants defining predefined or (or adaptively determined) ‘fixed’ beam patterns, directivity data, e.g. reference-indicators, etc., according to the present disclosure, together defining or facilitating the calculation or selection of appropriate beamformer weights and thus the beamformed signal Y(k) in dependence of the current electric input signals (cf. e.g. FIG. 4).

(51) The hearing aid of FIG. 5 may constitute or form part of a hearing aid and/or a binaural hearing aid system according to the present disclosure.

(52) The hearing aid (HD) according to the present disclosure may comprise a user interface UI, e.g., as shown in the lower part of FIG. 5, implemented in an auxiliary device (AUX), e.g. a remote control, e.g. implemented as an APP in a smartphone or other portable (or stationary) electronic device. In the embodiment of FIG. 5, the screen of the user interface (UI) illustrates a Target direction APP. A direction (TD) to the present target sound source (S) of interest to the user may be selected from the user interface, e.g. by dragging the sound source symbol (S) to a currently relevant direction relative to the user. The currently selected target direction is the frontal direction as indicated by the bold arrow (denoted TD) to the sound source S. The auxiliary device (AUX) and the hearing aid are adapted to allow communication of data representative of the currently selected direction to the hearing aid via a, e.g. wireless, communication link (cf. dashed arrow WL2 to wireless transceiver WLR.sub.2 in FIG. 8). The communication link WL2 may e.g. be based on far field communication, e.g. Bluetooth or Bluetooth Low Energy (or similar technology), implemented by appropriate antenna and transceiver circuitry in the hearing aid (HD) and the auxiliary device (AUX), indicated by transceiver unit WLR.sub.2 in the hearing aid. Other aspects related to the control of hearing aid (e.g. the beamformer) may be made selectable or configurable from the user interface (UI).

(53) FIG. 6 shows an embodiment of a binaural hearing aid system according to the present disclosure. The hearing aid system may be adapted for being worn by a user (U). The hearing aid system comprises first and second hearing aids (HD1, HD2), each being adapted to be located at or in an ear of the user. Each of the first and second hearing aids comprises at least two (here two) microphones (M.sub.1, M.sub.2), providing respective first and second (e.g. digitized) electric input signals (IN.sub.1, IN.sub.2) representing sound around the user (U) wearing the hearing aid system. The first and second microphones (M.sub.1, M.sub.2) may form part of a linear or non-linear microphone array. In the embodiment of FIG. 6, the first and second microphones (M.sub.1, M.sub.2) define a microphone axis, which, when the hearing aid (HD1, HD2) is mounted on the user at an ear (cf. schematic user (U) between the first and second hearing aids) is parallel to a look direction (cf. arrow denoted LOOK-DIR) of the user (U). Each of the first and second hearing aids (HD1, HD2) comprises first and second analysis filter banks (FBA1, FBA2) for converting the at least two electric input signals (IN.sub.1, IN.sub.2) into frequency sub-band signals (IN.sub.1, IN.sub.2) as a function of time (l) and frequency (k), e.g. represented by complex-valued time-frequency units (k,l) arranged in consecutive time frames, each time frame comprising a spectrum of the signal at a specific time l′. A spectrum at a given time l′ may e.g. comprise complex values (magnitude and phase) of the signal at a number of frequencies k=1, where K is the number of frequency bins in the spectrum (e.g. provided by a Fourier transform algorithm). Each of the first and second hearing aids (HD1, HD2) comprises a directional system (BF, beamformer filter) receiving the two electric input signals (IN.sub.1, IN.sub.2) from microphones (M.sub.1, M.sub.2) of the hearing aid itself and at least one further electric input signal (IN.sub.HD2, e.g. a signal from a microphone or a beamformed signal), received via a wireless link (cf. dashed double arrow denoted IA-WL) from the other hearing aid of the hearing aid system (or via a wireless link (e.g. WL2 in FIG. 5) from another device (e.g. AUX in FIG. 5), e.g. a smartphone, in communication with the hearing aid in question). The directional system (BF) is configured to provide a filtered signal Y in dependence of said at least three electric input signals (IN.sub.1, IN.sub.2, IN.sub.HD2) and fixed or adaptively updated beamformer weights (W.sub.1, W.sub.2, W.sub.HD2). Each of the first and second hearing aids (HD1, HD2) comprises appropriate transceiver circuitry (Rx/Tx) for establishing a communication link (IA-WL) allowing data (e.g. including audio data IN.sub.HD1, IN.sub.HD2) to be exchanged between the first and second hearing aids (HD1, HD2), e.g. including one or more microphone signals (IN.sub.1, IN.sub.2) or combinations thereof, in the form of one or more spatially filtered signal(s) (or parts thereof, e.g. selected frequency ranges thereof). The hearing aid system is configured to provide that at least one direction (TD) to a target sound source is defined as a target direction (and provided via a user interface (UI) (cf. signal TD and dashed arrow between user interface (UI) and block REF.fwdarw.WGT-CALC) and/or estimated by an algorithm of the hearing aid (e.g. in block REF.fwdarw.WGT-CALC). A multitude of algorithms for estimating a direction of arrival (DOA) of a target (speech) signal have been proposed in the prior art (see e.g. EP3413589A1). The directional system (BF) comprises a reference signal-and-beamformer weight-calculation unit (REF.fwdarw.WGT-CALC) configured to select a reference a reference input signal for each frequency band (k, k=1, . . . , K) among the at least three electric input signals (IN.sub.1, IN.sub.2, IN.sub.2) (and to adaptively update such selection over time in dependence of a current direction to the target signal source). The hearing aid (e.g. the directional system (BF) may comprise a voice activity detector for estimating whether or not, or with what probability, an input signal comprises a voice signal at a given point in time. Thereby an adaptive estimation of the frequency dependent filter weights W (for an exemplary MVDR beamformer) based on noise covariance matrices (R.sub.v, in the absence of speech) and transfer functions (d, when speech is detected) can be provided:

(54) $W_{\mathrm{mvdr}}\left(k\right)=\frac{{\hat{R}}_v^{-1}\left(k\right)\hat{d}\left(k\right)}{{\hat{d}}^H\left(k\right){\hat{R}}_v^{-1}\left(k\right)\hat{d}\left(k\right)}$
where {circumflex over (R)}.sub.v(k) is an estimate of the inter-microphone noise co-variance matrix R.sub.v frequency band k, and {circumflex over (d)}(k) is an estimate of the steering (or look) vector d for frequency band k. The hearing aid (e.g. the directional system (BF)) is configured to continuously update the selection of reference signal (and the filter coefficients) in dependence of the current electric input signals (and thus of the direction to the target sound source of current interest of the user). The direction to the target signal may be provided by the user via a user-interface and/or adaptively determined by the hearing aid, e.g. based on the electric input signals and the voice activity detector. The reference microphone signal for a given frequency band k may be determined according to a specific (e.g. logic) criterion, e.g. in dependence of directional data of the respective physical or virtual microphones, or in dependence of estimates of the acoustic transfer functions d(k) for the current target direction (TD), cf. also arrow denoted TD from target signal source (TD) to the user (U). Frequency dependent directional data (e.g. directivity index, or front-back-ratio) or estimates of the acoustic transfer functions d(k) (e.g. relative acoustic transfer functions) for a number of predefined target directions (TD) may be stored in a memory (MEM) of the hearing aid (or be accessible in an external database via a communication link) for use in estimation of the reference microphone signal in a given frequency band and for subsequent determination of filter weights W(k), cf. signal P(k,TD) between memory (MEM) and the reference signal-and-beamformer weight-calculation unit (REF.fwdarw.WGT-CALC). The target direction (TD) may be indicated as an angle θ in a horizontal plane (e.g. through the ears of the user) from a center of the user's head to the target sound source (S) of current interest to the user (U).

(55) In the embodiment of FIG. 6, the reference signal-and-beamformer weight-calculation unit (REF.fwdarw.WGT-CALC) of the first hearing aid (HD1) is configured to determine filter weights W.sub.1, W.sub.2, W.sub.HD2. And to apply the weights to respective electric input signals IN.sub.1, IN.sub.2, IN.sub.HD2 via respective combination units (multiplication units ‘x’). The resulting weighted signals are combined in a combination unit (sum-unit ‘+’), thereby providing filtered (beamformed) signal Y. The reference signal-and-beamformer weight-calculation unit (REF.fwdarw.WGT-CALC) of the second hearing aid (HD2) is configured to correspondingly provide filter weights W.sub.1, W.sub.2, W.sub.HD1, where the filter weights are applied to the (local) input signals IN.sub.1, IN.sub.2, and to signal IN.sub.HD1 received from the first hearing aid.

(56) The (frequency dependent) spatially filtered (beamformed) signal Y may be further processed in a hearing aid signal processor (SPU) of the forward path, e.g. adapted to a hearing impairment of the user (at the ear in question). The frequency dependency of the filtered signal Y is schematically indicated by differently hatched beamformers denoted k=1, . . . , K associated with Y. The forward path further comprises a synthesis filter bank (FBS) for converting the band-split (frequency domain) processed signal to a processed time-domain signal (OUT) that is fed to an output transducer (possibly after digital to analogue conversion, as appropriate), here loudspeaker (SPK), for presentation as stimuli perceivable by the user (U) as sound (here acoustic stimuli).

(57) In the embodiment of FIG. 6, the first and second hearing aids (HD1, HD1) may be identical, possibly except for specific adaptation to the left and right ears of the user (e.g. according to possible different hearing profiles of the left and right ears of the user resulting in differently parameterized compression algorithms (and possibly other algorithms) applied in the hearing aid signal processor (SPU) of the forward path).

(58) Instead of selecting the reference microphone signal in dependence of microphone location characteristics (as e.g. directional data or acoustic transfer functions), the hearing aid or the (possibly binaural) hearing aid system may be adapted (e.g. in a specific mode of operation, e.g. selected from a user interface (UI)) to select the reference microphone in dependence of the intended application of the filtered signal Y. Different intended applications of the filtered signal may e.g. include a) own voice detection, b) own voice estimation, c) keyword detection, d) target signal cancellation, target signal focus, noise reduction, etc.

(59) Further, the binaural hearing aid system may be adapted (e.g. in a specific ‘monaural mode of operation, e.g. entered via a user interface (UI)) to select the reference microphone (or reference microphone signal) independently in the first and second hearing aids (e.g. only selecting among ‘its own microphones’).

(60) It is intended that the structural features of the devices described above, either in the detailed description and/or in the claims, may be combined with steps of the method, when appropriately substituted by a corresponding process.

(61) As used, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well (i.e. to have the meaning “at least one”), unless expressly stated otherwise. It will be further understood that the terms “includes,” “comprises,” “including,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element but an intervening element may also be present, unless expressly stated otherwise. Furthermore, “connected” or “coupled” as used herein may include wirelessly connected or coupled. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

(62) The steps of any disclosed method are not limited to the exact order stated herein, unless expressly stated otherwise.

(63) It should be appreciated that reference throughout this specification to “one embodiment” or “an embodiment” or “an aspect” or features included as “may” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Furthermore, the particular features, structures or characteristics may be combined as suitable in one or more embodiments of the disclosure. The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects.

(64) The claims are not intended to be limited to the aspects shown herein but are to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more.

(65) The described idea of allowing the selection of a reference microphone (or reference signal) from an array of microphones in connection with a beamformer to vary over frequency bands (k) is exemplified above by a single hearing aid. The concept may, however, as well be applied to a binaural hearing aid system or a system containing external microphones (e.g. located in one or more external devices, e.g. in a smartphone). Different combinations of reference microphones may depend on the application of the beamformed signal (left ear may select a reference microphone only within the left-hearing instrument microphones, similarly for right ear. Further, a beamformed signal used for detection (e.g. keywords) may select between all available microphones in the microphone array.

REFERENCES

(66) EP3229489A1 (Oticon) 11 Oct. 2017 EP2701145A1 (Retune, Oticon) 26 Feb. 2014. [Brandstein & Ward; 2001] M. Brandstein and D. Ward, “Microphone Arrays”, Springer 2001. EP3413589A1 (Oticon) 12 Dec. 2018