Abstract
A hearing device comprises an ITE-part adapted for being located at or in an ear canal of the user comprising a housing comprising a seal towards walls or the ear canal, the ITE part comprising at least two microphones located outside the seal and facing the environment, and at least one microphone located inside the seal and facing the ear drum. The hearing device may comprise a beamformer filter connected to said at least three microphones comprising a first beamformer for spatial filtering said sound in the environment based on input signals from said at least two microphones facing the environment, and a second beamformer for spatial filtering sound reflected from the ear drum based on said at least one electric input signal from said at least one microphone facing the ear drum and at least one of said input signals from said at least two microphones facing the environment.
Claims
1. A hearing device configured to be located at or in an ear of a user, the hearing device comprising an ITE-part adapted for being located at or in an ear canal of the user, the ITE-part comprising a housing configured to be located at least partially in the ear canal of the user, at least three input transducers for providing respective electric input signals, wherein at least two outer input transducers face the environment and provide respective electric input signals representing sound in an environment of the user, and at least one inner input transducer is located closer to an ear drum than said at least two output input transducers, the at least one inner input transducer providing at least one electric input signal representing sound reflected from the ear drum, when the ITE-part is operationally mounted at or in the ear canal; an output transducer for providing stimuli perceivable to the user as sound based on said electric input signals or a processed version thereof; a beamformer filtering unit connected to said at least three input transducers and to said output transducer, and configured to provide a spatially filtered signal based on said at least three electric input signals and appropriate beamformer weights; wherein said beamformer filtering unit comprises a first beamformer for spatial filtering said sound in the environment based on said electric input signals from said at least two outer input transducers facing the environment, and a second beamformer for spatial filtering sound reflected from the ear drum based on said at least one electric input signal from said at least one inner input transducer facing the ear drum and at least one of said electric input signals from said at least two outer input transducers facing the environment.
2. A hearing device according to claim 1 configured to provide that the first and second beamformers are simultaneously available.
3. A hearing device according to claim 1 wherein the first and/or second beamformers is/are adaptive.
4. A hearing device according to claim 1 wherein the housing comprises a seal towards walls of the ear canal so that the ITE part fits tightly to the walls of the ear canal or at least provides a controlled or minimal leakage channel for sound.
5. A hearing device according to claim 4 wherein the at least two outer input transducers and the at least one inner input transducer are located on each side of the seal.
6. A hearing device according to claim 1 configured to provide each of said respective electric input signals in a time-frequency representation (k,m) as frequency sub-band signals X.sub.i(k,m), i=1, . . . , M, where M is the number of input transducers, where k and m are frequency and time indices, respectively, and where k=1, . . . , K.
7. A hearing device according to claim 1 wherein beamformer weights for different frequency channels may be used for different purposes.
8. A hearing device according to claim 7 configured to provide that the directional system is used for feedback cancellation in frequency channels, where feedback is dominant, while the directional system is used for noise reduction of external noise sources or microphone noise in frequency channels, where feedback is not significant.
9. A hearing device according to claim 1 wherein the ITE-part comprises a vent to minimize the occlusion effect.
10. A hearing device according to claim 4 wherein the at least two outer microphones are located outside the sealing facing the environment, and at least one inner microphone is located inside the seal and facing the ear drum.
11. A hearing device according to claim 1 comprising a feedback estimation unit providing feedback estimates of current feedback paths from said output transducer to each of said at least three input transducers.
12. A hearing device according to claim 1 comprising a signal processor for enhancing the input signals and providing a processed output signal.
13. A hearing device according to claim 1 adapted to provide a frequency dependent gain and/or a level dependent compression and/or a transposition of one or more frequency ranges to one or more other frequency ranges, to compensate for a hearing impairment of the user.
14. A hearing device according to claim 1 configured to pick up the user's own voice via a predefined or adaptive beamformer focusing on the mouth of the user.
15. A hearing device according to claim 1 configured to pick up the user's own voice via a predefined or adaptive beamformer focusing on the mouth of the user.
16. A hearing device according to claim 1 comprising an own voice beamformer focused on the user's mouth and an environment sound beamformer focused on a sound source of interest in the environment of the user, which are simultaneously created using the electric input signals.
17. A hearing device according to claim 1 wherein the at least two outer input transducers consist of first and second outer microphones facing the environment and at least one inner input transducer is a third microphone facing the ear drum, and wherein said first beamformer consists of two adaptively determined weighting units for applying respective weights to the two electric input signals from the outer microphones, to provide first and second weighted electric input signals, and a first summation unit for adding said first and second weighted electric input signals to provide a first spatially filtered signal; and wherein said second beamformer consists of two weighting units for adaptively determining and applying respective weights to said first spatially filtered signal and to the electric signal from the inner microphone to provide third and fourth weighted electric input signals, and a second summation unit for adding said third and fourth weighted electric input signals to provide a second spatially filtered signal; and wherein said output transducer is a loudspeaker, whose input is connected to an output of the second summation unit.
18. A hearing device according to claim 1 consisting of or comprising a hearing aid, a headset, an ear protection device or a combination thereof.
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) FIGS. 1A and 1B show a hearing device containing two microphones located in the ear canal adapted for cancelling sound propagated by the feedback path by applying a fixed or an adaptive directional gain,
(3) FIG. 2 shows an embodiment of a two-microphone MVDR beamformer according to the present disclosure,
(4) FIG. 3 illustrates a hearing device comprising a beamformer filtering unit according to the present disclosure, where the beamformer filtering unit provides a target cancelling beamformer for cancelling sound from a target signal in the acoustic far-field as illustrated by the cardioid,
(5) FIG. 4 shows a further embodiment of a two-microphone MVDR beamformer as illustrated in FIG. 2,
(6) FIG. 5 schematically shows an embodiment of a RITE-type hearing device according to the present disclosure comprising a BTE-part, an ITE-part and a connecting element,
(7) FIG. 6 shows a schematic block diagram of an embodiment of a hearing device comprising two microphones according to the present disclosure,
(8) FIG. 7A shows an embodiment of a hearing device comprising two microphones located in an ITE-part according to the present disclosure;
(9) FIG. 7B shows a schematic block diagram of an embodiment of a hearing device as shown in FIG. 7A;
(10) FIG. 7C shows an embodiment of a hearing device comprising three microphones located in an ITE-part according to the present disclosure;
(11) FIG. 7D shows a schematic block diagram of an embodiment of a hearing device as shown in FIG. 7C;
(12) FIG. 7E shows an embodiment of a hearing device comprising four microphones, two located in a BTE part and two located in an ITE-part according to the present disclosure;
(13) FIG. 7F shows a schematic block diagram of an embodiment of a hearing device as shown in FIG. 7E,
(14) FIG. 8A shows an embodiment of a hearing device comprising three microphones located in an ITE-part according to the present disclosure;
(15) FIG. 8B shows a schematic block diagram of an embodiment of a hearing device as shown in FIG. 8A, and
(16) FIG. 9A shows a first embodiment of a hearing device comprising two input transducers (e.g. microphones) used for cancelling noise in the environment as well as feedback from the output transducer (e.g. a loudspeaker) to the input transducers (microphones);
(17) FIG. 9B shows a second embodiment of a hearing device comprising two input transducers used for cancelling noise in the environment as well as feedback from the output transducer to the input transducers; and
(18) FIG. 9C shows a third embodiment of a hearing device comprising two input transducers used for cancelling noise in the environment as well as feedback from the output transducer to the input transducers.
(19) 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.
(20) 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.
DETAILED DESCRIPTION OF EMBODIMENTS
(21) 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.
(22) The electronic hardware may include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. 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.
(23) The present application relates to the field of hearing devices, e.g. hearing aids, in particular to feedback from an output transducer to an input transducer of the hearing device.
(24) EP2843971A1 deals with a hearing aid device comprising an “open fitting” providing ventilation, a receiver arranged in the ear canal, a directional microphone system comprising two microphones arranged in the ear canal at the same side of the receiver and means for counteracting acoustic feedback on the basis of sound signals detected by the two microphones. An improved feedback reduction can thereby be achieved, while allowing a relatively large gain to be applied to the incoming signal.
(25) In state of the art hearing aids omnidirectional microphones are known to provide satisfactory audiological performance for very small hearing instruments located almost invisibly in the ear canal entrance. It is also known that for slightly bigger hearing aids with microphones placed further out in the ear or behind the pinna, increased audiological performance can be obtained from the use of a directional microphone system. Such a directional system is able to distinguish between sounds coming from the frontal area seen from the hearing aid users' perspective and sounds from other directions in the horizontal plane. Hence from a conventional point of view, CIC hearing instruments only have one microphone and larger ITE instruments often have two microphones for directional performance.
(26) Both the small CIC and the larger ITE hearing instruments have limited acoustic gain from incoming sound at the microphone to the acoustic receiver output. This gain is limited by feedback problems due to unwanted signal transmission from the receiver back into the microphone. This problem may be alleviated by anti-feedback systems based on feedback path estimation; this is well known.
(27) An anti-feedback solution based on spatial resolution of the signal has is proposed in the present disclosure.
(28) Feedback in hearing aids is typically reduced by subtracting the estimated feedback path from the microphone signal. Often hearing aids contain more than one microphone. Hereby, the spatial information of the microphones may be used to remove feedback. In an aspect, we consider a special microphone configuration (cf. FIG. 1), which is well suited for directional feedback cancellation without altering the target signal.
(29) FIG. 1 shows a hearing device containing two microphones located in the ear canal adapted for cancelling sound propagated by the feedback path by applying a fixed or an adaptive directional gain.
(30) Adaptive beamforming in hearing instruments aims at cancelling unwanted noise under the constraint that sounds from the target direction is unaltered. An example of such an adaptive system is illustrated in FIG. 2, where the output signal in the k'th frequency channel Y(k) is based on a linear combination of two fixed beamformers C.sub.1(k) and C.sub.2(k), i.e. Y(k)=C.sub.1(k)−β(k) C.sub.2(k), where C.sub.1(k) and C.sub.2(k) preferably are orthogonal beamformers, and while C.sub.1(k) preserves the target direction, C.sub.2(k) is a beamformer, which cancel sound from the target direction.
(31) FIG. 2 shows an embodiment of a two-microphone MVDR beamformer according to the present disclosure. Based on the two microphones, two fixed beamformers are created: a beamformer C.sub.1 which do not alter the signal from the target direction, and an (orthogonal) beamformer C.sub.2 which cancels the signal from the target direction. The resulting directional signal Y(k)=C.sub.1(k)−β(k)C.sub.2(k), where
(32)
(33) minimizes the noise under the constraint that the signal from the target direction is unaltered. LP denotes an averaging of the signals, e.g. achieved by a 1st order IIR lowpass filter.
(34) The adaptation factor β(k) is a weight applied to the target cancelling beamformer. Hereby, we can adapt β(k) knowing that the target direction is unaltered. In the case where we would like to cancel feedback, all external sounds are considered as sounds of interest. With the chosen microphone configuration, all external sounds will pass the first microphone before it reaches the second microphone, as illustrated in FIG. 3.
(35) FIG. 3 shows a hearing device comprising a beamformer filtering unit according to the present disclosure, where the beamformer filtering unit provides a target cancelling beamformer for cancelling sound from a target signal in the acoustic far-field as illustrated by the cardioid. The cardioid is here illustrated as a directional pattern, but in fact, the beam pattern not only depends on the source direction; it also changes as function of distance between the sound source and the microphones. The target cancelling beamformer is configured to cancel signals impinging the hearing aid. Due to the microphone configuration, external sounds first have to pass the first microphone and secondly have to pass the second microphone. Seen from the hearing aid, most external sounds will thus have approximately the same delay. Hereby the target cancelling beamformer will work efficiently for most target directions.
(36) Another difference between the external sound and the feedback sound is that the feedback sound most likely has the highest sound pressure level at the inner microphone while the external sounds most likely have the highest sound pressure level at the outer microphone. In an embodiment, the hearing device is configured to compare the levels of the inner and outer microphones at a given point in time (e.g. when feedback is detected).
(37) In other words, all external sounds may (seen from the hearing instrument microphones) be considered as a sound from one distinct direction. We thus propose to estimate the target cancelling beamformer such that it minimizes sounds imping from all external directions. This may e.g. be achieved based on impulse response recordings of external sounds from various external directions (e.g. to determine predefined weights based on measurements). Alternatively, the target cancelling beamformer may be estimated based on a response from the preferred direction (i.e. choose one direction and determine a fixed beamformer (e.g. beamformer weights) for this direction, preferably the front direction, or the own voice direction). A third option is to adapt the target cancelling beamformer to the current listening direction, i.e. at any time cancel the external sound. Such an adaptive target cancelling beamformer could be updated whenever the external sound is much louder than the feedback signal. The task of the target cancelling BF is to estimate the ‘noise’, which is the feedback ‘from the ear drum’. Due to compression, we have relatively less feedback at high external input levels compared to low input levels, as we typically need less amplification at high input levels.
(38) Contrary to the typical update of the adaptive coefficient β(k), which is based directly on the microphone signals, we propose to update the coefficient based on the feedback path estimates.
(39) The advantage is that the adaptive beamformer hereby will depend less on external sounds. A disadvantage may be that the beamformer relies on the feedback path estimates, and for that reason cannot react faster than the feedback path estimates. Still, it is likely that the adaptive beamformer will be able to attenuate the feedback path estimate even though the beampattern is not perfectly adapted.
(40) Some feedback path estimates are more reliable than others. Hereby not all values of β(k) will represent a likely feedback. Considering the adaptation value β(k) may thus provide an estimate on how reliably the current (single microphone) feedback path estimates are.
(41) FIG. 4 shows a further embodiment of a two-microphone MVDR beamformer as illustrated in FIG. 2. The beamformer filtering unit is based on two fixed beamformers: a beamformer C.sub.1 which does not alter the signal from the target direction, and an (orthogonal) beamformer C.sub.2 which cancels the signal from the target direction. The target direction is the direction of all external sounds, which, due to the microphone configuration, may be seen as a single direction. The resulting directional signal is still given by Y(k)=C.sub.1(k)−β(k)C.sub.2 (k), but contrary to FIG. 2, the adaptation factor β(k) is estimated based on another set of fixed beamformers having the same weights (w.sub.11, w.sub.21, w.sub.12, w.sub.22) but in this case applied to the (frequency domain) feedback path estimates ({circumflex over (F)}.sub.1, ![custom character]()
) as input. The adaptation factor is thus given by
(42)
(43) The advantage of using the feedback path estimates contrary to the microphone signals is that the update of the adaptive beam pattern will be less affected by external sounds.
(44) FIG. 5 schematically shows an embodiment of a hearing device according to the present disclosure. The hearing device (HD), e.g. a hearing aid, is of a particular style (sometimes termed receiver-in-the ear, or RITE, style) comprising a BTE-part (BTE) adapted for being located at or behind an ear of a user, and an ITE-part (ITE) adapted for being located in or at an ear canal of the user's ear and comprising a receiver (loudspeaker). The BTE-part and the ITE-part are connected (e.g. electrically connected) by a connecting element (IC) and internal wiring in the ITE- and BTE-parts (cf. e.g. wiring Wx in the BTE-part).
(45) In the embodiment of a hearing device in FIG. 5, the BTE part comprises two input units (M.sub.BTE1, M.sub.BTE2, cf. also e.g. M2, M2 in FIG. 2, 3, 4) comprising respective input transducers (e.g. microphones), each for providing an electric input audio signal representative of an input sound signal (S.sub.BTE) (originating from a sound field S around the hearing device). The input unit further comprises two wireless receivers (WLR.sub.1, WLR.sub.2) (or transceivers) for providing respective directly received auxiliary audio and/or control input signals (and/or allowing transmission of audio and/or control signals to other devices). The hearing device (HD) comprises a substrate (SUB) whereon a number of electronic components are mounted, including a memory (MEM) e.g. storing different hearing aid programs (e.g. parameter settings defining such programs, or parameters of algorithms, e.g. optimized parameters of a neural network) and/or hearing aid configurations, e.g. input source combinations (M.sub.BTE1, M.sub.BTE2, WLR.sub.1, WLR.sub.2), e.g. optimized for a number of different listening situations. The substrate further comprises a configurable signal processor (DSP, e.g. a digital signal processor, including a processor (e.g. for hearing loss compensation (HLC)), feedback suppression (FBC) and beamformers (BFU) and other digital functionality of a hearing device according to the present disclosure). The configurable signal processing unit (DSP) is adapted to access the memory (MEM) and for selecting and processing one or more of the electric input audio signals and/or one or more of the directly received auxiliary audio input signals, based on a currently selected (activated) hearing aid program/parameter setting (e.g. either automatically selected, e.g. based on one or more sensors and/or on inputs from a user interface). 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, 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 configurable signal processor (DSP) provides a processed audio signal, which is intended to be presented to a user. The substrate further comprises a front-end IC (FE) for interfacing the configurable signal processor (DSP) to the input and output transducers, etc., and typically comprising interfaces between analogue and digital signals. The input and output transducers may be individual separate components, or integrated (e.g. MEMS-based) with other electronic circuitry.
(46) The hearing device (HD) further comprises an output unit (e.g. an output transducer) providing stimuli perceivable by the user as sound based on a processed audio signal from the processor (HLC) or a signal derived therefrom. In the embodiment of a hearing device in FIG. 5, the ITE part comprises the output unit in the form of a loudspeaker (receiver) for converting an electric signal to an acoustic (air borne) signal, which (when the hearing device is mounted at an ear of the user) is directed towards the ear drum (Ear drum), where sound signal (S.sub.ED) is provided. The ITE-part further comprises a guiding element, e.g. a dome, (DO) for guiding and positioning the ITE-part in the ear canal (Ear canal) of the user. The ITE-part further comprises a further input transducer, e.g. a microphone (M.sub.ITE), for providing an electric input audio signal representative of an input sound signal (S.sub.ITE). In an embodiment, the ITE-part comprises two or more input transducers configured as discussed in the present disclosure (cf. FIG. 1-4, 6-8).
(47) The electric input signals (from input transducers M.sub.BTE1, M.sub.BTE2, M.sub.ITE) may be processed according to the present disclosure in the time domain or in the (time-) frequency domain (or partly in the time domain and partly in the frequency domain as considered advantageous for the application in question). In an embodiment, one degree of freedom is used to suppress the external noise, and the other degree of freedom is used to suppress the feedback, see e.g. FIG. 7C, 7D.
(48) The hearing device (HD) exemplified in FIG. 5 is a portable device and further comprises a battery (BAT), e.g. a rechargeable battery, e.g. based on Li-Ion battery technology, e.g. for energizing electronic components of the BTE- and possibly ITE-parts. In an embodiment, the hearing device, e.g. a hearing aid (e.g. the processor (HLC)), is adapted to provide a frequency dependent gain and/or a level dependent compression and/or a transposition (with or without frequency compression) of one or more frequency ranges to one or more other frequency ranges, e.g. to compensate for a hearing impairment of a user.
(49) FIG. 6 shows a schematic block diagram of an embodiment of a hearing device comprising two microphones according to the present disclosure. The hearing device, e.g. a hearing aid, comprises first and second input transducers (e.g. located in an ear canal as shown in FIG. 1A or FIG. 3), here microphones (M1, M2), providing respective (e.g. digitized) electric input signals, IN1, IN2, representing sound in an environment of the user. The input units are via an electric forward path connected to an output transducer, here loudspeaker (‘receiver’) (SP) for converting a processed electric signal, OUT, to stimuli perceivable to the user as sound based on the electric input signals or a processed version thereof. The forward path comprises respective analysis filter banks (FB-A1, FB-A2) for converting respective (time domain) electric input signals ER1, ER2 (being feedback corrected versions of respective electric input signals IN1, IN2) (as explained below) to frequency sub-band signals X.sub.1, X.sub.2. The forward path of the hearing device (HD) further comprises an adaptive beamformer filtering unit (BFU) receiving the frequency sub-band signals X.sub.1, X.sub.2 and estimates of the feedback paths EST1, EST2 from the output transducer to respective first and second input transducers (as described below). The adaptive beamformer filtering unit (BFU) is configured to provide spatially filtered signal Y.sub.BF based on the electric input signals, the feedback estimates, and adaptively updated beamformer weights (e.g. based on the feedback estimates according to the present disclosure).
(50) The hearing device further comprises a feedback estimation unit (FBE) providing feedback estimates (EST1, EST2) of current feedback paths from the output transducer (SP) to each of the input transducers (M1, M2). The hearing device is configured to provide that at least one of the adaptively updated beamformer weights of the adaptive beamformer filtering unit (BFU) is/are updated in dependence of the feedback path estimates (EST1, EST2) as proposed by the present disclosure. The feedback estimation unit (FBE) comprises respective first and second adaptive filters, each comprising a variable filter part (FIL1, FIL2) and a prediction error or update or algorithm part (ALG1, ALG2) aimed at providing a good estimate of the ‘external’ feedback path from the (input to the) output transducer (SP) to the (output from the) respective input transducers (M1, M2). The respective prediction error algorithms (ALG1, ALG2) uses a reference signal (here the output signal OUT) together with a signal originating from the respective microphone signal to find the setting (reflected by filter update signals UP1, UP2 in FIG. 6) of the adaptive filter (FIL1, FIL2) that minimizes the prediction error, when the reference signal (OUT) is applied to the respective adaptive filter. The estimate of the feedback paths (EST1, EST2) provided by the respective adaptive filter are subtracted from the respective electric input signals IN1, IN2 from the microphones (M1, M2) in respective sum units ‘+’, providing so-called ‘error signals’ (or feedback-corrected signals ERR1, ERR2), which are fed to the beamformer filtering unit (BFU) (via respective analysis filter banks FB-A1, FB-A2) and to the respective algorithm parts (ALG1, ALG2) of the adaptive filters.
(51) The hearing device (HD) further comprises control unit (CONT) for controlling the feedback estimation unit (FBE), cf. control signals A1ctr, A2ctr, and the beamformer filtering unit (BFU). The control unit (CONT) is e.g. configured to control the adaptation rate of the adaptive algorithm (e.g. defined by the points in time where the feedback estimate is determined (and updated), cf. signals UP1, UP2). In the embodiment of FIG. 6, the control unit (CONT) may further comprise detectors for classifying a current acoustic environment of the user, e.g. a current feedback situation, e.g. indicating the degree of correlation between the electric input signal (or a signal derived therefrom) and the electric output signal. The control unit (CONT) may e.g. comprise a correlation detection unit for determining the auto-correlation of a signal of the forward path or the cross-correlation between two different signals of the forward path. The control unit (CONT) may further comprise other detectors, e.g. a speech detector, a feedback detector, a tone detector, an audibility detector, a feedback change detector, etc. Preferably, the hearing device (e.g. the control unit CONT or the algorithm part (ALG1, ALG2)) comprises a memory for storing a number of previous estimates of the feedback path, in order to be able to rely on a previous estimate, if a current estimate is judged (e.g. by the control unit CONT) to be less optimal. The control unit may store or have access to via a memory (MEM) to a number of beamformer filtering coefficients (cf. signal W). The stored beamformer filtering coefficients may comprise a first set of complex frequency dependent weighting parameters w.sub.11(k), w.sub.12(k) representing the first beam former (C.sub.1), and a second set of complex frequency dependent weighting parameters w.sub.21(k), w.sub.22(k) representing a second beam former (C.sub.2), as discussed in connection with FIGS. 2 and 4 above (k representing a frequency index). The first and second sets of weighting parameters w.sub.11(k), w.sub.12(k) and w.sub.21(k), w.sub.22(k), respectively, may be predetermined, e.g. used as initial values. In an embodiment, the hearing device (e.g. the control unit CONT) is configured to adaptively update one or more of the weighting parameters w.sub.11(k), w.sub.12(k) and w.sub.21(k), w.sub.22(k) stored in the memory during operation of the hearing device.
(52) Further, the control unit (CONT) may comprises a mode input for selecting a particular mode of operation of the hearing device. Such mode may be selectable via a user interface and/or be automatically determined from a number of detector inputs (e.g. from a classifier of the acoustic environment, e.g. comprising one or more of an auto-correlation detector, a cross-correlation detector, a feedback detector, a voice detector, a tone detector, a feedback change detector, an audibility detector, etc.). The mode input may influence or form basis of control output(s) A1ctr, A1ctr, HAGctr from the control unit for controlling the adaptive algorithms of the feedback estimation unit and processing of the processor HLC. One mode of operation may be a communication mode, where the user's own voice is picked by a dedicated own voice beamformer and transmitted to another device, e.g. a telephone or hearing device worn by another person. Such own voice pickup may be performed instead of or in parallel to a normal operation of the beamformer filtering unit where the first and second microphones pick up sound from the environment (other than the user's own voice).
(53) The hearing device (HD) further comprises processor (HLC) for executing one or more processing algorithms (e.g. compressive amplification), e.g. to provide a frequency dependent gain and/or a level dependent compression and/or a transposition of one or more frequency ranges to one or more other frequency ranges, e.g. to compensate for a hearing impairment of a user. In the embodiment of FIG. 6, the processor (HLC) receives the spatially filtered (beamformed) signal Y.sub.BF and provides a processed signal Y.sub.G, which is fed to a synthesis filter bank (FB-S) for converting the signal Y.sub.G processed in a number (K, K being e.g. 16 or 64 or more) of frequency sub-bands to a processed time domain signal OUT, which is fed to the output transducer (here loudspeaker SP) (which may comprise appropriate digital to analogue conversion circuitry).
(54) In the embodiment of FIG. 6, signal processing in the analysis path (feedback estimation, etc.) is performed in the time domain. It may, however, be performed fully or partially in the frequency domain, depending on the particular application in question. In the embodiment of FIG. 6, signal processing in the forward path is performed partially in the time domain (feedback correction) and partially in the frequency domain (beamforming and hearing loss compensation).
(55) The hearing device of FIG. 6 is an embodiment of the slightly more general embodiment of a hearing device illustrated in FIG. 7B.
(56) FIG. 7A shows an embodiment of a hearing device (HD) comprising two microphones (M.sub.ITE1, M.sub.ITE2) located in an ITE-part according to the present disclosure. The ITE-part comprises a housing, wherein the two ITE-microphones (M.sub.ITE1, M.sub.ITE2) are located (e.g. in a longitudinal direction of the housing along an axis of the ear canal (cf. dotted arrow ‘Inward’ in FIG. 7A), when the hearing device (HD) is operationally mounted on or at the user's ear. The ITE-part further comprises a guiding element (‘Guide’ in FIG. 7A) configured to guide the ITE-part in the ear canal during mounting and use of the hearing device (HD). The ITE-part further comprises a loudspeaker (facing the ear drum) for playing a resulting audio signal to the user, whereby a sound field is generated in the residual volume. A fraction thereof is leaked back towards the ITE-microphones (M.sub.ITE1, M.sub.ITE2) and the environment. The hearing device (e.g. the ITE-part, which may constitute a part customized to the ear or the user, e.g. in form, or alternatively have a standardized form) comprises the various functional blocks of the hearing device (BFU, HLC, FBE). FIG. 7B shows a schematic block diagram of an embodiment of a hearing device as shown in FIG. 7A. The loudspeaker (SP), the beamformer filtering unit (BFU), the processor (HLC) and the feedback estimation unit (FBE) have the function described in connection with the embodiment of FIG. 6. The hearing device (HD) may be configured to be located in the soft part of the ear canal of the user. In an embodiment, the hearing device (HD) is configured to be located fully or partially in the bony part of the ear canal.
(57) FIG. 7C shows an embodiment of a hearing device comprising three microphones located in an ITE-part according to the present disclosure. FIG. 7D shows a schematic block diagram of an embodiment of a hearing device as shown in FIG. 7C. The embodiment of a hearing device (HD) of FIGS. 7C and 7D comprises three microphones (M.sub.ITE11, M.sub.ITE12, M.sub.ITE2) in an ITE-part. Two of the microphones (M.sub.ITE11, M.sub.ITE12) face the environment, and one microphone (M.sub.ITE2) faces the ear drum (when the hearing device is operationally mounted). The hearing device comprising, or being constituted by, an ITE-part comprising a sealing element for providing a tight seal (cf. ‘seal’ in FIG. 7C) towards the walls of the ear canal to acoustically ‘isolate’ the ear drum facing microphone (M.sub.ITE2) from the environment sound (S.sub.ITE) impinging on the ear canal (and hearing device), cf. FIG. 7C. The hearing device (HD) comprises the same functional elements as the embodiment of FIGS. 8A and 8B. The embodiment of FIG. 7D additionally comprises respective feedback cancellation systems (comprising combination units ‘+’ for subtracting the feedback estimates ESTBF and EST2 of the beamformed signal Y.sub.BF and the ear drum-facing microphone signal IN2, respectively. The environment facing microphone signals IN11, IN12 are fed to a first beamformer unit BFU1 providing a first (far-field) beamformed signal Y.sub.BF1. An estimate ESTBF of the feedback path for this ‘directional microphone’ (represented by the front facing microphones (M.sub.ITE11, M.sub.ITE12) and the first beamformer unit BFU1) is subtracted from the first (far-field) beamformed signal Y.sub.BF1 providing feedback corrected beamformed signal ERBF, which is fed to a second beamformer unit (BFU2). The signal IN2 from the ear drum facing microphone (M.sub.ITE2) is connected to combination unit ‘+’, where an estimate of the feedback path from the loudspeaker (SP) to the ear drum facing microphone (M.sub.ITE2) is subtracted, which provides a feedback corrected ear drum facing microphone signal ER2. This signal is fed to the second beamformer unit (BFU2), which provides a resulting far-field and feedback minimized, beamformed signal Y.sub.BF. Based on the input signals (ERBF, ER2) and the feedback estimates (ESTBF, EST2). The resulting beamformed signal YBF is (or may be) subject to one or more processing algorithms (e.g. compressive amplification to compensate for a hearing impairment of the user) in processor (HLC). The resulting processed signal OUT is fed to the output transducer (loudspeaker SP) and played to the user as a sound signal. The resulting processed signal OUT is also fed to the feedback estimation unit (FBE) as a reference signal.
(58) FIG. 7E shows an embodiment of a hearing device (HD) comprising four microphones, two (M.sub.BTE1, M.sub.BTE2) located in a BTE part (BTE) and two (M.sub.ITE1, M.sub.ITE2) located in an ITE-part (ITE) according to the present disclosure. The BTE-part is adapted to be located at or behind an ear (pinna) and the BTE-part is adapted to be located at or in an ear canal (of the same ear) of the user. The BTE-part and the ITE part are electrically connected (by wire or wirelessly). The ITE-part comprises a housing, wherein the two ITE-microphones (M.sub.ITE1, M.sub.ITE2) are located (e.g. in a longitudinal direction of the housing along an axis of the ear canal (cf. dotted arrow ‘Inward’ in FIG. 7E), when the hearing device (HD) is operationally mounted on or at the user's ear. The ITE-part further comprises a guiding element (‘Guide’ in FIG. 7E) configured to guide the ITE-part in the ear canal during mounting and use of the hearing device. The ITE-part further comprises a loudspeaker (facing the ear drum) for playing a resulting audio signal to the user, whereby a sound field SED is generated in the residual volume. A fraction thereof is leaked back towards the ITE-microphones (M.sub.ITE1, M.sub.ITE2) and the environment. The BTE-part comprises a housing wherein the two BTE-microphones (M.sub.BTE1, M.sub.BTE2) are located (e.g. in a top part of the housing so that they lie in a horizontal plane when mounted correctly at the user's ear (so that the microphone axis is parallel to a look direction of the user, cf. FIG. 7E).
(59) FIG. 7F shows a schematic block diagram of an embodiment of a hearing device as shown in FIG. 7E. The hearing device (e.g. the BTE-part and/or the ITE part) comprises processing units (cf. units FBE, BFU, HLC, in FIG. 7F) configured to process the microphone signals according to the present disclosure, including to estimate and minimize feedback from the loudspeaker (SP) to the microphones, and (at least in a certain mode of operation) to apply relevant beamforming to the microphone signals. The hearing device further comprises a processor (HLC) for applying relevant processing algorithms to the (possibly) beamformed signal Y.sub.BF. The processed signal OUT from the processor (HLC) is fed to the loudspeaker (SP) for presentation to the user, and to the feedback estimation unit (FBE) as a reference signal.
(60) As shown in FIG. 7F, the ITE-microphones (M.sub.ITE1, M.sub.ITE2) receive a sound field S.sub.ITE comprising feedback from the nearby loudspeaker, and provides ITE-microphones signals (IN.sub.ITE1, IN.sub.ITE2), which are fed to respective combination units (‘+’) where respective feedback estimates (EST.sub.ITE1, EST.sub.ITE2), are subtracted to provide feedback corrected ITE-microphone signals (ER.sub.ITE1, ER.sub.ITE2). The (feedback corrected) microphone signals from the ITE-microphones are used in the beamformer filtering unit (BFU) for providing one or more beamformers for use in cancelling or minimizing feedback in the resulting beamformed signal Y.sub.BF.
(61) As shown in FIG. 7F, the BTE-microphones (M.sub.BTE1, M.sub.BTE2) receive a sound field S.sub.BTE, comprising less feedback than the ITE-microphones, and provides BTE-microphones signals (IN.sub.BTE1, IN.sub.BTE2), which are fed to respective combination units (‘+’) where respective feedback estimates (EST.sub.BTE1, EST.sub.BTE2), are subtracted to provide feedback corrected BTE-microphone signals (ER.sub.BTE1, ER.sub.BTE2). The (feedback corrected) BTE-microphone signals (IN.sub.BTE1, IN.sub.BTE2) from the BTE-microphones are used in the beamformer filtering unit (BFU) for providing one or more beamformers directed towards the environment (e.g. a nearby speaker, or the user's mouth).
(62) The feedback estimation unit (FBE) is configured to provide respective estimates (EST.sub.BTE1, EST.sub.BTE2, EST.sub.ITE1, EST.sub.ITE2) of the feedback paths from the loudspeaker (SP) to each of the four microphones (M.sub.BTE1, M.sub.BTE2, M.sub.ITE1, M.sub.ITE2). The feedback estimates are based on the respective feedback corrected input signals (ER.sub.BTE1, ER.sub.BTE2, ER.sub.ITE1, ER.sub.ITE2), the processed output signal (OUT) and possibly on applied weights (WGT) in the beamformer filtering unit (BFU), cf. e.g. discussion in connection with FIG. 8.
(63) In general, microphones located in the BTE-part are good at extracting environmental noise from the background, whereas microphones located in the ITE-part are good at extracting feedback. In an embodiment, the hearing device of FIG. 5, or 7E, F may be configured to use the BTE microphones (e.g. M.sub.BTE1, M.sub.BTE2 in FIG. 7E, 7F) for estimate post-filter gains for reducing noise in a beamformer, e.g. a target cancelling beamformer based on the BTE-microphone signals (e.g. IN.sub.BTE1, IN.sub.BTE2 in FIG. 7F). The post-filter gains may e.g. be applied to a signal of the forward path of the hearing device, where the signal of the forward path is based on a feedback cancelling beamformer based on the two BTE-microphone signals (e.g. IN.sub.BTE1, IN.sub.BTE2 in FIG. 7F), or based on the ITE-microphone signals BTE-microphone signals (e.g. IN.sub.ITE1, IN.sub.ITE2 in FIG. 7F), or a combination of BTE- and ITE-microphone signals. Such configuration is further discussed in connection with FIG. 9A, 9B, 9C.
(64) The embodiments of FIGS. 7A, 7C and 7E may be representative of processing in the time-domain, but may alternatively comprise respective filter banks to provide processing in the (time-)frequency domain (e.g. based on Short Time Fourier Transform (STFT)), cf. e.g. embodiments of FIG. 6, and FIG. 9A, 9B, 9C, comprising respective analysis and synthesis filter banks).
(65) An Example:
(66) In the previous examples, two microphones have been included oriented along an axis going from the outer ear opening and into the ear canal towards the eardrum. The signals from this microphone pair is subjected to a beamformer which is adjusted to process far field sounds originating from outside the ear as in a single omnidirectional microphone system and at the same time suppress the feedback signal (which is generated in the near field) received through the directional microphone system. Hence, in this way exceptionally high feedback suppression is possible while receiving the far field sounds from the surroundings in much the same way as in a single microphone hearing instrument.
(67) Hence, the present disclosure, utilizes the additional anti-feedback performance which may be obtained from spatial signal separation as described for a two-microphone system in connection with FIG. 1-4, 6 above. In the following further embodiment, these principles are applied in a system with three microphones, two of which represent a conventional directional system as described above and where the third microphone is added for the purpose of spatial feedback suppression.
(68) FIG. 8A shows an embodiment of a hearing device comprising three microphones located in an ITE-part according to the present disclosure.
(69) FIG. 8B shows a schematic block diagram of an embodiment of a hearing device as shown in FIG. 8A.
(70) The proposed hearing instrument configuration is sketched in FIG. 8A. The hearing device (HD) comprises an ITE-part (ITE) comprising three input transducers, here microphones. The ‘outer microphones’ (M.sub.ITE11, M.sub.ITE12), located (e.g. in a housing of the ITE-part) to face the environment, e.g. at an opening of the ear canal (‘Ear canal’), provide directional information in order to enhance speech intelligibility of a target signal (and may contribute to reduction of noise from the environment). The inner microphone (M.sub.ITE2, located closest to the ear drum (cf. hatched ellipse denoted ‘Ear drum’, and dotted arrow denoted ‘Inward’ indicating a direction towards the inner ear/ear drum)) serves as a means of getting spatial anti-feedback information for increased audiological performance in terms of acoustic amplification. Preferably the ITE part comprises a seal towards the walls or the ear canal so that the ITE part fits tightly to the walls ear canal (or at least provides a controlled or minimal leakage channel for sound). The ITE-part may comprise a vent to minimize the occlusion effect. A purpose of the seal may further be to minimize environment noise in the sound field reaching the inner microphone (M.sub.ITE2), to avoid (re-)introducing environmental noise in the beamformed signal when the signal from the inner microphone (M.sub.ITE2) is combined with the signals of the outer microphones (M.sub.ITE11, M.sub.ITE12, cf. e.g. FIG. 8B).
(71) The spatial anti-feedback performance may be implemented as one spatial feedback system cf. beamformer filtering unit (dashed outline denoted BFU in FIG. 8B) consisting of the inner microphone (M.sub.ITE2) and the outer microphone pair (M.sub.ITE11, M.sub.ITE12) treated as one microphone (cf. signal Y.sub.FF in FIG. 8B). In this implementation the output signals from the two outer microphones may be averaged as a means of obtaining spatial anti-feedback for both microphones using only one anti-feedback system. Alternatively, the performance is further enhanced by the use of two separately optimised spatial anti-feedback systems. In this implementation, two sets of optimizations are done—one for microphones M.sub.ITE11 and M.sub.ITE2, (see FIG. 8A) and one for microphones M.sub.ITE12 and M.sub.ITE2.
(72) If we regard the outer microphones (M.sub.ITE11, M.sub.ITE12) as a single microphone unit, we assume that the microphone system has one joint feedback path. If, however we have an adaptive microphone system, the resulting joint feedback path will change depending on the directional weights. If we know an estimate of the two outer acoustical feedback paths (h1, h2 (impulse response) or H1, H2 (frequency response)) as well as the directional weights (w1, w2), we can calculate the joint outer feedback path, which we then can use to adapt the directional pattern in connection with the feedback path of the inner microphone (as explained in the following).
(73) In case the beamformer filtering unit (BFU) represents an adaptive directional system, the joint feedback path of the two external ITE microphones (M.sub.ITE11, M.sub.ITE12), will change depending on the adaptive directional system. h1 and h2 are the impulse responses of the acoustic feedback path, and w1 and w2 are the adaptive weights of the directional system (BFU1, may as well be realized in the frequency domain).
(74) As the joint adaptive system is given by w1*h1+w2*h2, the (joint) feedback path may change solely depending on the adaptive parameters of the directional system (even though h1 and h2 are kept constant).
(75) The adaptive weights (or impulse responses) of the directional feedback cancellation system (w3 and w4) shall thus be adapted according to this change, and may thus depend on w1, w2 as well as (fixed or adaptive) estimates of the feedback paths (h1, h2 and h3).
(76) FIG. 9A, 9B, 9C illustrates three different embodiments of hearing devices according to the present disclosure. Each of the hearing devices (HD) comprises two input transducers (here microphones M1, M2) used for cancelling noise in the environment as well as feedback from an output transducer (e.g. as here a loudspeaker SP) to the input transducers (M1, M2) according to an aspect of the present disclosure. The embodiments of FIG. 9A, 9B, 9C each comprises a microphone array comprising at least two microphones (M1, M2) positioned in a way such that the microphone array can be used to cancel external noise as well as feedback. The at least two microphones may e.g. comprise two BTE microphones (e.g. arranged as M.sub.BTE1, M.sub.BTE2 in FIG. 7E), or two ITE microphones (e.g. arranged as M.sub.ITE11, M.sub.ITE12 in FIG. 7C), or two BTE microphones (e.g. arranged as M.sub.BTE1, M.sub.BTE2 in FIG. 7E) and one ITE microphone (e.g. arranged as M.sub.ITE in FIG. 5, or as M.sub.ITE2 in FIG. 7C), or three ITE microphones (e.g. as illustrated in FIG. 7C).
(77) FIG. 9A shows a first embodiment of a hearing device (HD) comprising two microphones (M1, M2) used for cancelling noise in the environment as well as feedback from a loudspeaker (SP) to the microphones (M1, M2). The microphone signals (x.sub.1, x.sub.2) are propagated through respective analysis filter banks (FBA) in order to obtain a frequency domain representation (X.sub.1, X.sub.2) of the two microphone signals. The frequency-domain microphone signals are processed in two beamformer units (BFU1 and BFU2). The first beamformer unit has two output signals—C.sub.1, which (possibly adaptively) enhances a target sound from a given direction, and a target cancelling beamformer C.sub.2 which cancels the sound from a given target direction. The two directional signals are propagated into a post filter block (PF) used to estimate a signal to noise ratio, which is converted into a gain (G), which varies across time and frequency (G=G(k,m), where k and m are frequency and time indices, respectively, cf. e.g. EP2701145A1). The gain is multiplied to the output Y.sub.BF2 of the other beamforming unit (BFU2), which creates a (possibly adaptive) directional signal Y.sub.BF aiming at cancelling the feedback as well as noise in the environment. The resulting signal is converted back into a time domain signal OUT by use of a synthesis filter bank (AFS), and presented to the listener. Hereby, the post filter gain aims at removing external noise while the directional signal aims at removing feedback.
(78) FIG. 9B shows a second embodiment of a hearing device (HD) comprising two input transducers (M1, M2) used for cancelling noise in the environment as well as feedback from the output transducer (SP) to the input transducers (M1, M2). The embodiment of FIG. 9B resembles the embodiment of FIG. 9A, but is different in that it only comprises one beamformer unit (BFU) receiving the electric (frequency sub-band) input signals (X.sub.1, X.sub.2) from the microphones. The beamformer unit (BFU) provides beamformer C.sub.1, which (possibly adaptively) enhances a target sound from a given direction. The post filter (PF) converts the xx to a gain G, while attenuating ‘noise’ from the feedback paths. The resulting gains G are applied to the target signal C1 (cf. multiplication unit ‘x’) thereby providing the resulting beamformed signal which is converted to the time domain (signal OUT) in synthesis filter bank (SFB) and fed to the loudspeaker (SP) for presentation to the ear drum of the user. The directional signal C.sub.1 aims at removing noise in the external sound and the post filter gain G aims at removing the feedback signal. In that case, the noise estimate could be the feedback signals (cf. input signals FB1, FB2 to the post filter (FP)) (either a single feedback estimate, or a combination (e.g. a MAX value), rather than the target cancelling beamformer (C.sub.2, as in FIG. 9A)).
(79) FIG. 9C shows a third embodiment of a hearing device (HD) comprising two input transducers (M1, M2) used for cancelling noise in the environment as well as feedback from the output transducer (SP) to the input transducers (M1, M2). The embodiment of FIG. 9C is equal to the embodiment of FIG. 9B apart from the beamformer unit (BFU) in FIG. 9C being updated by respective feedback path estimates (FB1, FB2) from the loudspeaker SP to the microphones (M1, M2). In the embodiment of FIG. 9C, the directional system (BFU) as well as the post filter (PF) are adapted in order to minimize feedback (cf. input signals (FB1, FB2)).
(80) In the embodiments of a hearing device in FIG. 9A, 9B, 9C, the spatially filtered (beamformed) and noise reduced signal Y.sub.BF is presented to the user. It may of course be subject to other processing algorithms (e.g. compressive amplification to compensate for a hearing loss of the user) before presented to the user (cf. e.g. processor HLC in FIG. 6, or FIG. 7B, 7D, 7F).
(81) 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.
(82) 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 one or more intervening elements 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. The steps of any disclosed method are not limited to the exact order stated herein, unless expressly stated otherwise.
(83) 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.
(84) 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.
(85) Accordingly, the scope should be judged in terms of the claims that follow.
REFERENCES
(86) EP2843971A1 (OTICON) 4 Mar. 2015 EP2701145A1 (RETUNE DSP, OTICON) 26 Feb. 2014 EP3253075A1 (OTICON) 6 Dec. 2017
