Hearing aid including a directional microphone system

Abstract

The present application discloses a hearing aid including a directional microphone system. The hearing aid includes: a forward path, which includes at least two input transducers, a beamformer filter, a signal processor, and an output transducer; a feedback estimation system for estimating a current feedback from the output transducer to each of the at least two input transducers and providing a corresponding feedback metric indicating the feedback; a controller configured to receive the feedback metric from the feedback estimation system; wherein the controller is configured to switch between two operating modes of the hearing aid, namely a single input transducer operating mode and a multi-input transducer operating mode, according to the feedback metric.

Description

Technical Field

[0001] The present invention relates to hearing aids, such as hearing aids suitable for compensating for moderate to severe or severe to profound hearing loss. The present invention particularly relates to directivity and feedback in hearing aids. Background Art

[0002] EP3185589A1 discloses solutions for reducing or processing acoustic feedback from a receiver (loudspeaker) located in the ear canal to a microphone system, the microphone system including one or more microphones located at or behind the ear and one or more microphones located at or in the ear canal. Summary of the Invention

[0003] Hearing aid

[0004] The present invention relates to a hearing aid comprising a feedback estimation unit for controlling or influencing the directional or non-directional operating mode of the hearing aid.

[0005] A well-known problem is that when the loop gain exceeds 1, the hearing aid can become unstable and whistle. The (open) loop gain is the product of the gain in the hearing aid and the coupling between the receiver (loudspeaker) and the microphone, mainly but not exclusively through vents or other openings in the earphone. The vent (or other opening structure) is typically embedded in the earphone of the hearing aid to avoid (or reduce) the occlusion effect. The coupling between the receiver and the microphone is called the external or physical or acoustic feedback path and can have other sources different from the deliberately arranged vents, such as mechanical coupling between different parts of the earphone, etc.

[0006] The frequency-varying loop gain LG in a loop including a forward path and an electrical feedback path can be estimated as the sum of the (insertion) gain IG (also called "forward gain" (e.g., implemented by a signal processor such as Figure 1 , DSP or HLC in 2A, 2B, 3A, 3B)) in the forward path and the gain FBG in the electrical feedback path, with the aim of minimizing, preferably eliminating, the acoustic feedback between the receiver and the microphone of the hearing aid system (i.e., in logarithmic terms, LG(f) = IG(f) + FBG(f), where f is the frequency). In practice, the frequency range Δf = [f min ; f max , for example limited to a part of the typical human audible frequency range such as 20 Hz ≤ f ≤ 20 kHz, is divided into N frequency bands (FB), for example N ≥ 16, (FB1, FB2,..., FB N ), and the expression of the loop gain can be expressed according to the frequency band, i.e., LG(FB i ) = IG(FB i ) + FBG(FB i), i = 1, 2, …, N, or simply, LG i = IG i + FBG i .

[0007] For example, when a specific feedback criterion is met, such as when the current loop gain is greater than a threshold, e.g., 0 dB (possibly within a certain minimum time period, e.g., across a minimum number of time frames, e.g., ≥ 100 ms or ≥ 500 ms), it can enter the "critical feedback operating mode" via a user interface or automatically. In an embodiment, when entering the "critical feedback operating mode", a scheme that currently controls or affects the switching between the directional and non - directional operating modes is initiated. The control of the directional and non - directional operating modes can be per frequency band.

[0008] On one hand, a hearing aid including a forward path is provided. The forward path includes at least two input transducers (such as more than 2 microphones), a signal processor, and an output transducer. The hearing aid further includes a feedback estimation system for estimating the current feedback from the output transducer to each of the at least two input transducers and providing a corresponding feedback metric indicating the current feedback. At a given point in time, the at least two input transducers can experience different feedback paths (e.g., indicated by a feedback path difference metric being greater than a threshold), as determined by the feedback estimation system (or a controller connected to the feedback estimation system). The feedback path difference metric can indicate the difference between the corresponding feedback metrics (of two of the at least two input transducers). In the non - directional operating mode, the hearing aid is configured to select, at a given time, the electrical input signal from the input transducer with the minimum feedback metric as the electrical input signal to be processed in the forward path (thus providing a signal with the best possible feedback margin such that the maximum gain can be applied without the risk of howling).

[0009] In an embodiment, the hearing aid is configured to enter a single - input transducer (such as a single microphone) omnidirectional operating mode (e.g., for low input levels (high gain) or quiet environments) when the feedback path difference metric of two of the at least two input transducers is above a (first) threshold. In an embodiment, the hearing aid is configured to enter the multi - input transducer (directional) operating mode only when the feedback margin of all input transducers (such as microphones) allows it, e.g., including, for all pairs of input transducers (such as microphones) contributing to the directional system (i.e., connected to the beamformer), the feedback path difference metric is below a predetermined (second) threshold (or below the respective individual thresholds). In an embodiment, the hearing aid is fitted using ordinary fitting rationale (such as NAL or DSL or a proprietary fitting rationale such as Oticon's VAC) and is configured to use ordinary compression algorithms (such as compression amplification).

[0010] The solution according to the present invention has the advantage of enabling higher gain to be applied in, for example, ITE instruments (i.e., hearing aid types enclosed in a single, custom housing, adapted to be located in the ear (ITE), e.g., at or in the ear canal). For hearing-impaired users with moderate to severe or severe to profound hearing loss, ITE instruments including custom (snug-fitting) ear molds are particularly valuable (since such hearing instruments can generate large sound pressure levels at the user's eardrum and thus compensate for large hearing losses). When the placement of one of the microphones is less critical (e.g., when the microphone is located at a certain distance from the output transducer, e.g., in a BTE portion adapted to be located behind the ear (BTE)), the solution according to the present invention can be used, for example, to create smaller, super-power BTE-type hearing aids enabling the use of directivity. Alternatively, for hearing aids of the same size, the solution can improve the feedback performance.

[0011] In an embodiment, the hearing aid includes a BTE portion adapted to be located at or behind the user's ear (pinna) and an ITE portion adapted to be located at or in the user's ear canal. The BTE portion and the ITE portion are electrically or acoustically connected to each other. The BTE portion and the ITE portion may include at least one input transducer such as a microphone. The input transducer in the BTE portion and the input transducer in the ITE portion are generally positioned asymmetrically relative to the output transducer (located in the BTE portion or the ITE portion). The BTE portion may include at least two input transducers (such as microphones), and the ITE portion may include at least one input transducer such as a microphone. The BTE portion and the ITE portion may include at least two input transducers such as microphones.

[0012] The ITE portion may form part of a hearing aid including other parts such as the BTE portion. The BTE portion may include an output transducer. The ITE portion may constitute the hearing aid. The ITE portion may include an output transducer. The ITE portion may include at least two input transducers. The ITE portion may include a ventilation channel or opening (to reduce the user's perception of the occlusion effect). At least two input transducers in the ITE portion may be asymmetrically located in the ITE portion (such as in the housing of the ITE portion). Such an asymmetric location may be the result of design limitations caused by components of the hearing aid such as the battery (especially in a custom ITE portion). Thus, at least two input transducers (such as a first and a second microphone) may exhibit different feedback paths from the output transducer (such as a speaker).

[0013] The asymmetric positioning of the two input transducers relative to the output transducer means that they inherently exhibit different feedback paths. The different feedback paths can result from the asymmetric positioning of the input transducers relative to the output transducer (i.e., stationary, relatively stable, and inherently contributing to the feedback path difference). However, it can also be caused by asymmetric feedback situations (e.g., different acoustic effects on different input transducers (e.g., from reflective surfaces around the user), i.e., more dynamic asymmetric feedback situations).

[0014] The hearing aid according to the present invention may include a scheme for entering or exiting a directional operation mode (e.g., implementing a switch between an omnidirectional and a directional operation mode, the former providing a substantially omnidirectional signal and the latter providing a beamformed signal). This scheme can be used to control which of the beamformed signal or one of the electrical input signals from at least two (e.g., omnidirectional) input transducers is used as the signal presented to the user (after appropriate frequency / level-dependent amplification / attenuation by the signal processor).

[0015] In one aspect of the present application, there is provided a hearing aid adapted to be located at or in a user's ear and adapted to compensate for the user's hearing loss. The hearing aid may include:

[0016] - A forward path, including

[0017] -- At least two input transducers, each input transducer for picking up sound from the hearing aid environment and providing a corresponding at least two electrical input signals;

[0018] -- A beamformer filter for filtering the at least two electrical input signals or signals derived therefrom and providing a spatially filtered signal;

[0019] -- A signal processor for processing one or more of the electrical input signals or one or more signals derived from the electrical input signals (such as the spatially filtered signal), and providing one or more processed signals based thereon;

[0020] -- An output transducer for generating a stimulus perceptible as sound by the user based on one or more processed signals; and

[0021] - A feedback estimation system for estimating the current feedback from the output transducer to each of the at least two input transducers and providing a corresponding feedback metric indicating the feedback.

[0022] The hearing aid may further include a controller configured to receive the feedback metric from the feedback estimation system.

[0023] The controller can be configured to switch between two operating modes of the hearing aid, namely the single-input transducer (e.g., omnidirectional) operating mode and the multi-input transducer (directional) operating mode, according to a feedback metric such as a feedback path difference metric. The controller can be configured to switch between the aforementioned two operating modes in a critical feedback operating mode (where a feedback criterion is met, e.g., critical feedback has been detected or is estimated to occur).

[0024] The controller can be configured to:

[0025] - When the current feedback path difference metric between at least two of the feedback metrics is greater than a first threshold, select the electrical input signal from the input transducer with the smallest feedback metric among at least two input transducers or a signal derived therefrom as the input signal to the signal processor; and / or

[0026] - When the feedback path difference metric between each of the feedback metrics is less than a second threshold, select the spatially filtered signal as the input signal to the signal processor.

[0027] The controller can be configured to receive the feedback metric from a feedback estimation system and cause the hearing aid to enter the single-input transducer (e.g., omnidirectional) operating mode when the current feedback path difference metric between at least two feedback metrics is greater than the first threshold, and select the electrical input signal from the input transducer with the smallest feedback metric among at least two input transducers or a signal derived therefrom as the input signal to the signal processor.

[0028] The controller can be configured to receive the feedback metric from a feedback estimation system and cause the hearing aid to enter the multi-input transducer (e.g., directional) operating mode when the feedback path difference metric between each feedback metric is less than the second threshold, and select the spatially filtered signal as the input signal to the signal processor.

[0029] The controller can include a feedback path difference measurement unit configured to determine the corresponding feedback path difference metric (e.g., in the case of three input transducers IT1, IT2, IT3, FBDM 12 = FB1est - FB2est, FBDM 13 = FB1est - FB3est and FBDM 23 = FB2est - FB3est) and provide a selection control signal based thereon (e.g., according to a predetermined feedback criterion). The selection control signal can be configured to select an appropriate signal as the input signal to the signal processor (e.g., select between the omnidirectional and directional operating modes).

[0030] Thus, an improved hearing aid can be provided. Thus, the gain provided by the hearing aid to the user can be maximized (without a significant risk of howling).

[0031] The first and second thresholds may be equal. The first and second thresholds may be different. The first and / or second threshold may vary with frequency. The first and / or second threshold may be independent of frequency.

[0032] At least two input transducers may be positioned asymmetrically relative to the output transducer. This can be achieved, for example, when at least one of the at least two input transducers is located in the BTE part and at least one of the at least two input transducers is located in the ITE part. It can also be achieved when the at least two input transducers are located in the BTE part (and the output transducer is located in the BTE part or the ITE part) or when the at least two input transducers are located in the ITE part (and the output transducer is located, for example, in the BTE part or the ITE part).

[0033] The hearing aid may include at least three input transducers, for example two in the BTE part and one in the ITE part. The different positioning of the at least three input transducers increases the likelihood of identifying the input transducer with a relatively low feedback path (high gain margin) in many acoustic situations. A (directional) signal based on spatial filtering of the electrical input signals from the two input transducers located in the BTE part or a feedback-corrected version thereof may be provided. A (directional) signal based on spatial filtering of the electrical input signals from the two input transducers located in the BTE part and from the input transducer located in the ITE part or a feedback-corrected version thereof may be provided. The solution according to the invention can be used to select between: A) a single electrical input signal among at least three electrical input signals; and B) either: B1) a beamforming signal based on the BTE microphone signals or B2) a beamforming signal based on all three input signals (the selection between B1) and B2) can be determined, for example, predetermined or adaptively, for example according to a feedback criterion).

[0034] The feedback metric for a given input transducer may include, for example, the impulse response of a feedback path from an output transducer to the input transducer involved. The feedback metric for a given input transducer may include, for example, the frequency response of a feedback path from an output transducer to the input transducer involved, represented, for example, by a feedback gain (measured, for example, at multiple frequencies). The feedback path difference metric between two feedback paths (e.g., between the feedback paths of first and second input transducers such as microphones) may be based, for example, on the algebraic difference between the corresponding feedback metrics, such as the absolute value of such a difference. The feedback path difference metric may be, for example, the sum of the differences (or squared differences) of the corresponding values of the corresponding feedback metrics (e.g., the respective time samples of the corresponding impulse responses, or the respective values at different frequencies of the corresponding frequency responses). Alternatively, the feedback path difference metric may be based on other difference metrics, such as the ratio of two feedback path estimators, or the logarithm of such a ratio, etc. The feedback path difference metric may be based, for example, on a mathematical distance metric, such as Euclidian distance or the square of Euclidian distance. The feedback path difference metric for two feedback paths (to two input transducers) may be set such that the greater the algebraic difference (such as the absolute value of the difference) between the two feedback paths.

[0035] The feedback metric for a given input transducer may include the impulse response of a feedback path from an output transducer to the input transducer involved, or the frequency response of a feedback path from an output transducer to the input transducer involved, the latter being measured at multiple frequencies.

[0036] The feedback path difference metric between at least two feedback metrics may be based on the algebraic difference between the corresponding feedback metrics.

[0037] The feedback path difference metric may be determined as the sum of the differences or squared differences of the respective time samples of the corresponding impulse responses or the (corresponding) respective values at different frequencies of the corresponding frequency responses.

[0038] A hearing aid may be adapted to compensate for a user's moderate to severe or severe to profound hearing loss. Moderate hearing loss may be defined as a hearing loss in the range of 40 to 70 dB. Severe hearing loss may be defined as a hearing loss in the range of 70 to 90 dB. Profound hearing loss may be defined as a hearing loss in the range above 90 dB.

[0039] A hearing aid may include a BTE portion adapted to be located at or behind the user's ear (pinna) and an ITE portion adapted to be located in or at the user's ear canal, wherein the BTE portion and the ITE portion are electrically or acoustically connected to each other.

[0040] The BTE part and the ITE part may include at least one of the plurality of input transducers. The (DIR / OMNI) mode selection scheme according to the present invention may be applied to a hearing aid including a BTE part and an ITE part, each part including at least one or at least two input transducers.

[0041] The hearing aid may include an ITE part adapted to be located at or in the ear canal of a user, wherein the ITE part includes the at least two input transducers and the output transducer. The ITE part of the hearing device may include a (e.g., custom) housing (such as an ear mold). The housing may include a ventilation channel (e.g., see the vent in Figure 3B . In an embodiment, the design of the ITE part and the position of the vent and the input transducers may result in generally different feedback paths from the output transducer (see Figure 3B , microphone M1 is closer to the ventilation channel than microphone M2). A scheme for controlling the beamforming signal or the use of the signal from a single input transducer in the forward path of the hearing aid may be applied to the aforementioned ITE hearing aid to provide more design freedom in terms of the positioning of the input transducers relative to the ventilation channel. Thereby a greater maximum gain (e.g., a greater full-on gain) may be allowed. The hearing aid may be constituted by the ITE part (e.g., in an ITE style form, e.g., custom fit, e.g., in-the-ear-canal hidden (IIC) or completely-in-the-canal (CIC) or in-the-ear (ITC) hearing aid).

[0042] The hearing aid may include a filter bank. The hearing aid (such as a filter bank) may include or implement a time-domain to time-frequency-domain converter configured to provide at least two electrical input signals or signals derived therefrom as corresponding sub-band signals. The time-domain to time-frequency-domain converter may for example be provided in each input transducer path (see the "t / f" unit in Figure 2A ), to convert the (possibly digitized) electrical input signal (or its processed version) from a time-domain signal to a frequency-domain signal (including K sub-band signals, e.g., represented by the (complex) discrete values IN(k,m) of these signals, where k and m are frequency and time indices respectively). The processing of the signal in the forward path may for example be performed in the time-frequency domain. The hearing aid may include a synthesis filter bank to convert the sub-band signals to a time-domain signal (see the f / t unit in Figure 2A ). A distortionless filter bank for a hearing aid is for example described in EP3229490A1.

[0043] The beamformer filter may be configured to provide a spatially filtered signal as corresponding sub-band signals.

[0044] The beamformer filter may be configured to individually set the omnidirectional or directional mode in the corresponding sub-bands.

[0045] The hearing aid can be configured such that, based on the sub-band signals and the feedback criterion, the controller individually selects, for different frequency ranges, one of the spatially filtered signal or the electrical input signal or a signal derived therefrom as the input signal for the signal processor.

[0046] The feedback metric can indicate mechanical feedback. Selecting, as the input signal for the signal processor, one of the spatially filtered signal or the electrical input signal or a signal derived therefrom, as proposed in the present invention, can be used, for example, to increase the maximum full-on gain of the hearing aid.

[0047] The feedback metric can indicate acoustic feedback.

[0048] The first and second thresholds of the feedback path difference metric can be determined, for example, according to the user's hearing loss situation (and thus the necessary gain, e.g., provided by a fitting algorithm) for a given hearing aid of a given user.

[0049] In an embodiment, the first and second thresholds of the feedback path difference metric are pre-determined, for example, during fitting, where the processing parameters of the (particular type of) hearing aid are adapted to the user involved. However, the first and second thresholds of the feedback path difference metric can also be determined dynamically according to the currently requested gain and the current corresponding feedback metric.

[0050] The hearing aid can be adapted to provide frequency-dependent gain and / or level-dependent compression and / or frequency shifting (with or without frequency compression) from one or more frequency ranges to one or more other frequency ranges to compensate for the user's hearing impairment. The signal processor can be configured to enhance the electrical input signal representing the sound and provide a processed output signal. The signal processor can be configured to apply a plurality of processing algorithms to the electrical input signal.

[0051] The hearing aid includes an output transducer for providing, based on the processed electrical signal from the signal processor, a stimulus that is perceived by the user as an acoustic signal. The output transducer can include a receiver (loudspeaker) for providing the stimulus as an acoustic signal to the user. The output transducer can include a vibrator for providing the stimulus as a mechanical vibration of the skull to the user (e.g., in bone conduction such as in a bone-attached or bone-anchored hearing aid).

[0052] The plurality of input transducers can include one microphone or a plurality of microphones, each microphone for converting the input sound into an electrical input signal.

[0053] A hearing aid includes a directional microphone system (beamformer filter) that is adapted to spatially filter sounds from the environment to enhance a target sound source among a plurality of sound sources in the local environment of a user wearing the hearing aid. In an embodiment, the directional system is adapted to detect (e.g., adaptively detect) from which direction a particular portion of a microphone signal originates. This can be achieved in a variety of different ways described in the prior art, for example. In hearing aids, microphone array beamformers are typically used to spatially attenuate background noise sources. Many beamformer variants can be found in the literature, see, for example, [Brandstein & Ward; 2001] and the references cited therein. The minimum variance distortionless response (MVDR) beamformer is widely used in microphone array signal processing. Ideally, the MVDR beamformer leaves the signal from the target direction (also called the look direction) unchanged while maximally attenuating sound signals from other directions. The generalized sidelobe canceller (GSC) structure is an equivalent representation of the MVDR beamformer that offers computational and digital representation advantages over a direct implementation of the original form.

[0054] A hearing aid may include a wireless receiver for receiving a wireless signal including sound and for providing an electrical input signal representative of the sound. The hearing aid may include an antenna and transceiver circuitry adapted to establish a wireless link to another device such as another hearing aid or a communication device such as a smartphone. Preferably, the frequency used to establish a communication link between the hearing aid and another device is below 70 GHz. The wireless link may be based on a standardized or proprietary technology. The wireless link may be based on Bluetooth technology (such as Bluetooth Low Energy technology) or an equivalent technology.

[0055] The hearing aid may be portable such as a wearable device, for example a device including a native energy source such as a battery, for example a rechargeable battery.

[0056] A hearing aid includes a forward or signal path between an input transducer such as a microphone or microphone system and / or a direct electrical input (such as a wireless receiver) and an output transducer. A signal processor is located in this forward path. The signal processor is adapted to provide frequency-varying gain according to the specific needs of the user. The hearing aid may include an analysis path having functions for analyzing an input signal (such as determining level, modulation, signal type, acoustic feedback estimate, etc.). Part or all of the signal processing in the analysis path and / or the forward path may be performed in the frequency domain. Part or all of the signal processing in the analysis path and / or the signal path may be performed in the time domain.

[0057] The hearing aid may include an analog-to-digital (AD) converter to digitize an analog input (e.g., from an input transducer such as a microphone) at a predetermined sampling rate f s e.g., in a range from 8 kHz to 48 kHz (adapting to the specific needs of the application, e.g., 20 kHz). The AD converter samples the analog input at discrete time points t s in the range, for example, from 8 kHz to 48 kHz (adapting to the specific needs of the application, e.g., 20 kHz). The AD converter samples the analog input at discrete time points tn (or n) provides a digital sample x n (or x[n]). Each audio sample is represented by a predetermined N b bits to represent the value of the sound signal at t n when, N b for example, in the range from 1 to 48 bits, such as 24 bits. Each audio sample thus uses N b bits for quantization (resulting in 2 Nb different possible values of the audio sample). The digital sample x has a time length of 1 / f s , such as 50 μs, for f s = 20 kHz. Multiple audio samples can be arranged in time frames. A time frame can include 64 or 128 (or more) audio data samples. Other frame lengths can be used according to the actual application. In an embodiment, the hearing aid includes a digital-to-analog (DA) converter to convert the digital signal into an analog output signal, for example, for presentation to the user via an output transducer.

[0058] Hearing aids such as input transducers and / or antennas and transceiver circuits can include a time-frequency (TF) conversion unit, such as an analysis filter bank, for providing a time-frequency representation of the input signal. The time-frequency representation can include an array or mapping of the corresponding complex or real values of the signal involved in a specific time and frequency range (spectrogram). The TF conversion unit can include a filter bank for filtering the (time-varying) input signal and providing multiple (time-varying) sub-band signals, each sub-band signal including a distinct input signal frequency range. The TF conversion unit can include a Fourier transform unit for converting the time-varying input signal into a (time-) frequency domain (time-varying) signal. The frequency range considered by the hearing aid can range from a minimum frequency f min to a maximum frequency f max , which includes a part of the typical human audible frequency range from 20 Hz to 20 kHz, for example, at least a part of the range from 20 Hz to 12 kHz. Generally, the sampling rate f s is greater than or equal to twice the maximum frequency f max , that is, f s ≥ 2f max . In an embodiment, the signals in the forward path and / or analysis path of the hearing aid can be split into NI (e.g., uniformly wide) frequency bands, where NI is, for example, greater than 5, such as greater than 10, such as greater than 50, such as greater than 100, and at least some of them are processed individually. The frequency band widths can be uniform. The hearing aid can be adapted to process the signals in the forward and / or analysis paths in NP different channels (NP ≤ NI). The channels can have the same width or different widths (e.g., the width increases with frequency), and can overlap or not overlap.

[0059] In an embodiment, the hearing aid includes a plurality of detectors configured to provide status signals related to the current network environment of the hearing aid (such as the current acoustic environment), and / or related to the current state of the user wearing the hearing aid, and / or related to the current state or operating mode of the hearing aid. As an alternative or in addition, one or more of the detectors may form part of an external device that communicates with the hearing aid (such as wirelessly). The external device may include, for example, another hearing aid, a remote control, an audio transmission device, a telephone (such as a smart phone), an external sensor, etc.

[0060] In an embodiment, one or more of the plurality of detectors operate on the full-band signal (time domain). In an embodiment, one or more of the plurality of detectors operate on the frequency-band split signals ((time-)frequency domain), for example, in a finite number of frequency bands.

[0061] In an embodiment, the plurality of detectors includes a level detector for estimating the current level of the signal in the forward path. In an embodiment, the predetermined criterion includes whether the current level of the signal in the forward path is higher or lower than a given (L-)threshold. In an embodiment, the level detector operates on the full-frequency band signal (time domain). In an embodiment, the level detector operates on the frequency-band split signal ((time-)frequency domain).

[0062] In a particular embodiment, the hearing aid includes a voice detector (VD) for estimating whether (or with what probability) the input signal (at a particular time point) includes a voice signal. In this specification, a voice signal includes a speech signal from a human. It may also include other forms of vocalization generated by the human speech system (such as singing). In an embodiment, the voice detector unit is adapted to classify the user's current acoustic environment as a "voice" or "no voice" environment. This has the advantage that time periods of the microphone signal that include human vocalization (such as speech) in the user's environment can be identified and thus separated from time periods that include only (or mainly) other sound sources (such as artificially generated noise). In an embodiment, the voice detector is adapted to also detect the user's own voice as "voice". As an alternative, the voice detector is adapted to exclude the user's own voice from the detection of "voice".

[0063] In an embodiment, the hearing aid includes a self-voice detector for estimating whether (or with what probability) a particular input sound (such as a voice, such as speech) originates from the voice of the user of the hearing system. In an embodiment, the microphone system of the hearing aid is adapted to be able to distinguish the user's own voice from the voice of another person and possibly from a no-voice sound.

[0064] In an embodiment, the plurality of detectors includes a motion detector, such as an acceleration sensor. In an embodiment, the motion detector is configured to detect movements of the user's facial muscles and / or bones caused, for example, by speech or chewing (such as jaw movement) and provide a detector signal indicating the movement.

[0065] In an embodiment, the plurality of detectors includes a feedback detector. The feedback detector may be configured to estimate a feedback amount or a feedback risk. The feedback detector may be configured to indicate whether a specific feedback criterion is met. The feedback detector is described, for example, in EP3185588A1.

[0066] A hearing aid includes an acoustic (and / or mechanical) feedback control system. Acoustic feedback occurs because the output speaker signal from an audio system that provides amplification to a signal picked up by a microphone returns to the microphone via air or other medium through an acoustic coupling portion. This portion of the speaker signal that returns to the microphone is amplified again by the audio system before it reappears at the speaker, and then returns to the microphone again. As this cycle continues, when the audio system becomes unstable, the acoustic feedback effect becomes audible, such as unnatural signals or even worse, whistling. This problem typically occurs when the microphone and the speaker are placed close together, such as in a hearing aid or other audio system. Some other typical situations with feedback problems include telephony, broadcast systems, headphones, audio conferencing systems, etc. Adaptive feedback cancellation has the ability to track changes in the feedback path over time. It estimates the feedback path based on a linear time-invariant filter, but the filter weights are updated over time. The filter update can be calculated using a stochastic gradient algorithm, including certain forms of the least mean square (LMS) or normalized LMS (NLMS) algorithms. They all have the property of minimizing the mean square of the error signal, and NLMS additionally normalizes the filter update with respect to the square of the Euclidean norm of some reference signal.

[0067] In an embodiment, the feedback control system includes a feedback estimation unit for providing a feedback signal representing an estimate of the acoustic feedback path and a combining unit, such as a subtraction unit, for subtracting the feedback signal from the signal in the forward path (such as picked up by the input transducer of the hearing aid). In an embodiment, the feedback estimation unit includes an update part containing an adaptive algorithm and a variable filter part for filtering an input signal according to variable filter coefficients determined by the adaptive algorithm, wherein the update part is configured to update the filter coefficients of the variable filter part at a configurable update frequency f upd Update the filter coefficients of the variable filter part.

[0068] In an embodiment, the hearing aid further includes other suitable functions for the application involved, such as compression, noise reduction, etc.

[0069] Application

[0070] On the one hand, there is provided an application of a hearing aid as described above, detailed in the "Detailed Description" section and defined in the claims. In an embodiment, there is provided an application in a system including audio distribution, such as a system including a microphone and a speaker that are close enough to each other such that feedback from the speaker to the microphone is caused during user operation. In an embodiment, there is provided an application in a system including one or more hearing aids (such as hearing instruments), headsets, earphones, active ear protection systems, etc., for example, for use in a hands-free telephone system, a teleconference system, a broadcast system, a karaoke system, a classroom amplification system, etc.

[0071] Method

[0072] On the one hand, the present application further provides a method of operating a hearing aid, the hearing aid being adapted to be located at or in a user's ear and adapted to compensate for the user's hearing loss. The method includes:

[0073] - Providing at least two electrical input signals representing sounds picked up from the hearing aid environment by corresponding at least two input transducers;

[0074] - Providing a spatially filtered signal based on the at least two electrical input signals;

[0075] - Processing one or more of the electrical input signals or one or more signals derived from the electrical input signals and providing one or more processed signals based thereon;

[0076] - Generating a stimulus for an output transducer that can be perceived as sound by the user based on one or more processed signals;

[0077] - Estimating the current feedback from the output transducer to each of the at least two input transducers and providing a corresponding feedback metric indicating the feedback;

[0078] - Such that at a given time point

[0079] -- When the feedback path difference metric between at least two of the feedback metrics is greater than a first threshold, selecting the electrical input signal from the input transducer having the smallest feedback metric among the at least two input transducers or a signal derived therefrom as the input signal to be processed; and / or

[0080] -- When the feedback path difference metric between each of the feedback metrics is less than a second threshold, selecting the spatially filtered signal as the input signal to be processed.

[0081] On the other hand, there is provided a method of operating a hearing aid, the hearing aid being adapted to be located at or in a user's ear and adapted to compensate for the user's hearing loss. The method includes:

[0082] - Provide at least two electrical input signals representing sounds picked up from the hearing aid environment by the corresponding at least two input transducers;

[0083] - Provide a spatially filtered signal based on the at least two electrical input signals;

[0084] - Process one or more of the electrical input signals or one or more signals derived from the electrical input signals and, based thereon, provide one or more processed signals;

[0085] - Generate a stimulus for an output transducer that can be perceived as sound by a user based on one or more processed signals;

[0086] - Estimate the current feedback from the output transducer to each of the at least two input transducers and provide a corresponding feedback metric indicating said feedback;

[0087] - Switch between two operating modes of the hearing aid, namely a single input transducer (e.g., omnidirectional) operating mode and a multi-input transducer (directional) operating mode, according to the feedback metric.

[0088] When appropriately replaced by corresponding processes, some or all of the structural features of the device described above, detailed in the "Detailed Description" or defined in the claims, can be combined with the implementation of the method of the present invention, and vice versa. The implementation of the method has the same advantages as the corresponding device.

[0089] Hearing system

[0090] On the other hand, there is provided a hearing system comprising a hearing aid and an auxiliary device as described above, detailed in the "Detailed Description" and defined in the claims.

[0091] In an embodiment, the hearing system is adapted to establish a communication link between the hearing aid and the auxiliary device so that information (such as control and status signals, possibly audio signals) can be exchanged or forwarded from one device to another.

[0092] The auxiliary device may include a smart phone, or other portable or wearable electronic devices such as a smart watch, etc.

[0093] In an embodiment, the auxiliary device is or includes a remote control for controlling the functions and operations of the hearing aid. In an embodiment, the functions of the remote control are implemented in a smart phone, which may run an APP enabling the functions of controlling an audio processing device via the smart phone (the hearing aid includes an appropriate wireless interface to the smart phone, e.g., based on Bluetooth or some other standardized or proprietary scheme).

[0094] In an embodiment, the assisting device is or includes an audio transmission device such as an audio gateway device, which is adapted to receive a plurality of audio signals (e.g., from an entertainment device such as a TV or a music player, from a telephone device such as a mobile phone, or from a computer such as a PC) and is adapted to select and / or combine appropriate signals (or signal combinations) among the received audio signals for transmission to a hearing aid.

[0095] In an embodiment, the assisting device is or includes another hearing aid. In an embodiment, the hearing system includes two hearing aids adapted to implement a binaural hearing system such as a binaural hearing aid system.

[0096] APP

[0097] On the other hand, the present invention also provides a non-transitory application (such as a software program) called an APP. The APP includes executable instructions configured to run on the assisting device to implement a user interface for the hearing aid or the hearing system described above, detailed in the "Detailed Description" and defined in the claims. In an embodiment, the APP is configured to run on a mobile phone such as a smart phone or another portable device enabling communication with the hearing aid or the hearing system.

[0098] Definition

[0099] In this specification, a "hearing aid" refers to a device such as a hearing instrument or an active ear protection device or other audio processing device adapted to improve, enhance, and / or protect a user's auditory ability, which is achieved by receiving an acoustic signal from the user's environment, generating a corresponding audio signal, possibly modifying the audio signal, and providing the possibly modified audio signal as an audible signal to at least one ear of the user. The audible signal can be provided, for example, in the form of an acoustic signal radiated into the user's outer ear, or as a mechanical vibration transmitted through the bone structure of the user's head and / or through parts of the middle ear to the user's inner ear.

[0100] The hearing aid can be configured to be worn in any known manner, such as as a unit worn behind the ear (with a tube for guiding the radiated acoustic signal into the ear canal or with an output transducer such as a speaker arranged to be close to or in the ear canal), as a unit arranged wholly or partly in the auricle and / or the ear canal, as a unit connected to a fixed structure implanted in the skull such as a vibrator, or as a connectable or wholly or partly implantable unit, etc. The hearing aid can include a single unit or several units in electronic communication with each other. The speaker can be provided in a housing together with other components of the hearing aid, or it can itself be an external unit (possibly combined with a flexible guiding element such as a dome-shaped element).

[0101] More generally, a hearing aid includes an input transducer for receiving an acoustic signal from the user's environment and providing a corresponding input audio signal and / or a receiver for receiving the input audio signal electronically (i.e., wired or wirelessly), a (generally configurable) signal processing circuit (such as a signal processor, e.g., including a configurable (programmable) processor, e.g., a digital signal processor) for processing the input audio signal, and an output unit for providing an audible signal to the user based on the processed audio signal. The signal processor may be adapted to process the input signal in the time domain or in multiple frequency bands. In some hearing aids, an amplifier and / or a compressor may form part of the signal processing circuit. The signal processing circuit typically includes one or more (integrated or separate) storage elements for executing programs and / or for storing parameters used (or potentially used) in the processing and / or for storing information suitable for the function of the hearing aid and / or for storing information used, for example, in connection with an interface to the user and / or to a programming device (such as processed information, e.g., provided by the signal processing circuit). In some hearing aids, the output unit may include an output transducer, such as a loudspeaker for providing an air-borne acoustic signal or a vibrator for providing a structure- or fluid-borne acoustic signal.

[0102] In some hearing aids, the vibrator may be adapted to transmit a structure-borne acoustic signal to the skull transcutaneously or through the skin. In some hearing aids, the vibrator may be implanted in the middle ear and / or inner ear. In some hearing aids, the vibrator may be adapted to provide a structure-borne acoustic signal to the middle ear bones and / or the cochlea. In some hearing aids, the vibrator may be adapted to provide a fluid-borne acoustic signal to the cochlear fluid, for example, through the oval window.

[0103] The hearing aid may be adapted to the needs of a particular user, such as hearing impairment. The configurable signal processing circuit of the hearing aid may be adapted to apply compression amplification that varies with frequency and level to the input signal. Customized gain (amplification or compression) that varies with frequency and level may be determined during the fitting process by a fitting system based on the user's hearing data, such as an audiogram, using fitting principles (e.g., adapted to speech). The gain that varies with frequency and level may be embodied, for example, in processing parameters, e.g., uploaded to the hearing aid via an interface to a programming device (fitting system) and used by a processing algorithm executed by the configurable signal processing circuit of the hearing aid.

[0104] "Hearing system" refers to a system including one or two hearing aids. "Binaural hearing system" refers to a system including two hearing aids and adapted to provide audible signals to a user's two ears cooperatively. The hearing system or binaural hearing system may also include one or more "auxiliary devices" which communicate with the hearing aids and affect and / or benefit from the functions of the hearing aids. The auxiliary device may be, for example, a remote control, an audio gateway device, a mobile phone (such as a smart phone) or a music player. The hearing aid, hearing system or binaural hearing system may be used, for example, to compensate for the loss of auditory ability of a hearing-impaired person, enhance or protect the auditory ability of a person with normal hearing and / or transmit an electronic audio signal to a person. The hearing aid or hearing system may form a part of or interact with, for example, a broadcast system, an active ear protection system, a hands-free telephone system, an automotive audio system, an entertainment (such as karaoke) system, a teleconference system, a classroom amplification system, etc. Description of the Drawings

[0105] The various aspects of the present invention will be best understood from the following detailed description taken in conjunction with the accompanying drawings. For clarity, these drawings are all schematic and simplified, showing only the details necessary for understanding the present invention and omitting other details. Throughout the specification, the same reference numerals are used for the same or corresponding parts. The features of each aspect may be combined with any or all of the features of other aspects. These and other aspects, features and / or technical effects will be apparent from and elucidated in conjunction with the following drawings, in which:

[0106] Figure 1 A first embodiment of a hearing aid according to the present invention is shown;

[0107] Figure 2A A second embodiment of a hearing aid according to the present invention is shown;

[0108] Figure 2B A third embodiment of a hearing aid according to the present invention is shown;

[0109] Figure 3A A fourth embodiment of a hearing aid according to the present invention is shown;

[0110] Figure 3B A fifth embodiment of a hearing aid according to the present invention is shown;

[0111] Figure 4A A relationship curve between the mechanical feedback metric (M-FB) and frequency of the hearing aid is schematically shown, in which the full-on gain parameter (FOG) is illustrated; and

[0112] Figure 4B A relationship between exemplary first and second feedback metrics (FBM) and frequency is schematically shown.

[0113] The further scope of applicability of the present invention 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 invention, are given by way of illustration only, since various other embodiments will be apparent to those skilled in the art from the following detailed description. Detailed Description of the Invention

[0114] The following detailed description presented in connection with the accompanying drawings is used as a description of various different configurations. The detailed description includes specific details for providing a thorough understanding of the various different 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 different blocks, functional units, modules, elements, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements"). Depending on a particular application, design constraints, or other reasons, these elements may be implemented using electronic hardware, computer programs, or any combination thereof.

[0115] Electronic hardware may include a microprocessor, a microcontroller, a digital signal processor (DSP), a field programmable gate array (FPGA), a programmable logic device (PLD), gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various different functions described in this specification. A computer program should be construed broadly as instructions, instruction sets, code, code segments, program code, programs, subroutines, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, execution threads, programs, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0116] This application relates to the field of hearing aids.

[0117] A well-known problem in hearing aids is feedback. This involves a) (mechanical) feedback related to the internal hardware, which determines the limit of the full-on gain (FOG) measured in a 711 / 2 cc coupler (IEC 711 compliant coupler) used in the data sheet; and b) acoustic feedback, which is typically observed as a whistling sound.

[0118] There are various different ways to handle the feedback problem, including using digital signal processing for dynamic feedback cancellation and using tools in the fitting software (at frequencies where the hearing aid or the type of hearing aid involved is prone to feedback) to reduce the gain.

[0119] However, for hardware-related feedback, the design choices for hearing aids are typically the following choices: A) reducing the full-on gain (FOG), B) selecting a new transducer and / or C) improving the mechanical design.

[0120] The full-on gain (FOG) parameter is an important feature for controlling the stability of a digital hearing aid by limiting the maximum allowable gain in the hearing aid. The full-on gain limit is a characteristic of the hearing aid hardware and represents the maximum gain that can be applied to the hearing aid without causing mechanical feedback. The determination of the full-on gain is typically carried out according to a predefined, e.g., standardized procedure (such as ANSI S3.22-2003: Specification of Hearing Aid Characteristics), for example, using the gain control of the hearing aid set to its full-on position and using an input sound pressure level (SPL) of 50 dB. As an alternative, the measurement conditions may be specified in the hearing aid's data sheet together with the limited full-on gain (FOG) value.

[0121] Figure 1 An embodiment of a hearing aid according to the present invention is shown. The hearing aid HD is adapted to be located at or in the user's ear and is adapted to compensate for the user's hearing loss. The hearing aid includes a forward path for processing an input signal representing sound in the environment. The forward path includes at least two input transducers (such as microphones (M1, M2)), each input transducer for picking up sound from the environment of the hearing aid and providing a corresponding at least two electrical input signals (IN1, IN2). The forward path also includes a beamformer filter BFU for filtering the at least two electrical input signals or signals derived therefrom and providing a spatially filtered signal IN BF . The forward path also includes a signal processor HLC for processing one or more of the electrical input signals (IN1, IN2) or one or more signals derived from the electrical input signals (such as the spatially filtered signal IN BF ), and providing one or more processed signals OUT on the basis of the processing. The forward path also includes an output transducer OT (such as a loudspeaker) for generating a stimulus STIM (such as an acoustic stimulus) perceptible by the user as sound based on the one or more processed signals OUT. The hearing aid HD also includes a feedback estimation system FE for estimating the current feedback paths (FBP1, FBP2) from the output transducer OT to each of the at least two input transducers (M1, M2) and providing corresponding feedback metrics (FBE1, FBE2) indicating the feedback. Each of the microphones (M1, M2) picks up sound, which is a mixture of "external sound" (x1, x2) from the environment and sound (v1, v2) leaking back to the microphone via the respective acoustic feedback paths (FBP1, FBP2) from the output transducer OT (see the acoustic summing unit "+" to the left of the respective microphones (M1, M2) in the figure). The hearing aid also includes a controller CTR configured to receive the feedback metrics (FBE1, FBE2), the electrical input signals (IN1, IN2), and the beamforming signal IN BF, possibly the requested gain (or insertion gain IG) from the signal processor HLC. The hearing aid may include a loop gain estimator for estimating the current loop gain. Using the current estimate of the feedback path from the output transducer to the microphone and the currently requested gain for compensating the user's hearing impairment, it can be checked whether specific feedback criteria for entering the critical feedback operating mode are met (e.g., if LG ∼ FBE + IG ≥ 0 dB, enter the critical feedback mode). In the critical feedback mode, the controller may be configured such that when the feedback path difference metric determined by the comparison of at least two of the feedback metrics is greater than a first threshold FBDM TH1 at (e.g., FBDM 12 = FBE1 - FBE2 > FBDM TH1 ), the electrical input signal (IN1; IN2) from the input transducer with the smallest feedback metric (or gain margin) among at least two input transducers (M1, M2) is selected as the input signal IN to the signal processor HLC. In the critical feedback mode, the controller CTR may also be configured such that when the feedback path difference metric determined by the comparison of each of the feedback metrics is less than a second threshold FBDM TH2 at (e.g., FBDM 12 = FBE1 - FBE2 < FBDM TH2 ), the spatially filtered signal IN BF is selected as the input signal IN to the signal processor HLC. In an embodiment, FBDM TH1 = FBDM TH2 . In an embodiment, FBDM TH1 ≥ FBDM TH2 . The (fully) "digital components" of the hearing aid (e.g., components different from the input and output transducers) are surrounded by a dashed box and denoted as DSP, e.g., see the digital signal processor DSP in Figure 3A .

[0122] Figure 2A shows an embodiment of the hearing aid HD according to the present invention, similar to the embodiment of Figure 1 . However, in the embodiment of Figure 2A , the hearing aid HD is divided into a BTE part and an ITE part. The BTE part is, for example, adapted to be located at or behind the user's ear (pinna). The ITE part is, for example, adapted to be located in or in the user's ear canal. The hearing aid HD may belong to a specific type, sometimes called "Receiver In The Ear" (RITE), because the ITE part includes a speaker OT (often called a "receiver" in the hearing aid field). Figure 2A 's embodiment includes three input transducers, two microphones (M BTE1 , M BTE2 ) located in the BTE part and another input transducer ITITE (such as a microphone, an accelerometer, or a similar element for picking up vibrations) is located in the ITE part. The BTE part and the ITE part are electrically connected by conductors for connecting the signal processor HLC to the output transducer OT and for connecting the input transducer IT ITE to the beamformer filter BFU and for powering (at least) the input transducer. A third input transducer IT located in the ITE part ITE receives the mixture of the external sound (or vibration) x3 and the feedback signal v3 from the output transducer OT via the feedback path FB3. In addition to the two microphones (M BTE1 , M BTE2 ) and the electrical inputs from the input transducer IT located in the ITE part ITE , the BTE part further includes the beamformer filter BFU, the feedback estimation system FE, the controller CTR, and the signal processor HLC as combined Figure 1 therewith. In Figure 2A , the three functional units BFU, CTR, and FE are shown as one unit (enclosed by a box denoted BFU-CTR-FE). Additionally, each of the three (time-domain) inputs (IN BTE1 , IN BTE2 , IN ITE ) of the beamformer filter BFU from the corresponding input transducers (M BTE1 , M BTE2 , IT ITE ) includes a corresponding analysis filter bank t / f for providing the time-domain signal as a sub-band signal for individual processing in the forward path of the hearing aid (here the BTE part). Similarly, the output path OUT includes a synthesis filter bank f / t for converting the sub-band signal into a time-domain signal OUT, and the time-domain signal is forwarded to the output transducer OT (such as a loudspeaker, in the ITE part) via the cable of the connecting element. The presence of the three input transducers increases the possibility of performing proper beamforming, such as directing the beam towards the user's mouth (e.g., in the case of a telephone). The different positions of the three input transducers increase the possibility of identifying the input transducer with a relatively low feedback path (high gain margin) in many acoustic situations. In an embodiment, the directional signal IN' based on the two BTE microphone signals IN BTE1 and IN BTE2 or their feedback-corrected versions (ERR1 and ERR2) can be used as the first microphone signal, and the input signal IN ITE from the ITE microphone IT ITEOr a feedback-corrected version ERR3 thereof can be used as the second microphone signal. The solution according to the invention can be used to select between a beamformed signal IN' based on the BTE microphone signal and a beamformed signal IN based on all three input signals according to a predetermined feedback criterion in a critical feedback operating mode.

[0123] Figure 2B Shows an embodiment of a hearing aid HD according to the invention, similar to the Figure 1 and 2A illustrated embodiment. The difference is that Figure 2B 's embodiment also includes a feedback control system (denoted as FBC (curved solid box) in Figure 2B ), which includes corresponding adaptive filters (FBE1, FBE2, FBE3) and a combining unit ('+') (which also includes a beamformer control unit BFU-CTR here, and the latter can be excluded from the feedback control system in other embodiments). The three adaptive filters (FBE1, FBE2, FBE3) are configured to adaptively estimate three feedback paths (FBP1, FBP2, FBP3) from the output transducer OT to the three input transducers (IT BTE1 , IT BTE2 , IT ITE ) respectively. The three subtraction units ('+') are configured to subtract the three feedback path estimates (FB1est, FB2est, FB3est) from the electrical input signals (IN BTE1 , IN BTE2 , IN ITE ) respectively, so as to provide corresponding feedback-corrected input signals (ERR1, ERR2, ERR3). The feedback-corrected input signals (ERR1, ERR2, ERR3) are fed to the beamformer control unit BFU-CTR. The feedback path estimates (FB1est, FB2est, FB3est) are fed to the feedback path difference measurement unit FBPD, which is configured to determine corresponding feedback path difference metrics (here for example FBDM 12 = FB1est - FB2est, FBDM 13 = FB1est - FB3est and FBDM 23 = FB2est - FB3est) and provide a selection control signal SMctr according to it (for example according to a predetermined criterion). The selection control signal SMctr is fed to the beamformer control unit BFU-CTR (possibly together with a requested gain IG from the signal processor HLC) for selecting one of the feedback-corrected input signals (ERR1, ERR2, ERR3) or a beamformed signal that is provided as a combination of the three feedback-corrected input signals (for example see IN Figure 1 in BF)。Based on the selection, the beamformer control unit BFU-CTR provides the resulting signal IN for further processing in the processor HLC (e.g., according to the needs of the hearing aid user) and presentation to the user. The beamformer filtering unit may include, for example, a beamformer algorithm of the generalized sidelobe canceller (GSC) type, such as a beamformer algorithm of the minimum variance distortionless response (MVDR) type. The beamformer filtering unit may provide, for example, a non-linear combination of the input signals, for example, implemented by a trained neural network.

[0124] Figure 3A An embodiment of a BTE type hearing aid according to the present invention is shown. As described in connection with Figure 2A , 2B , the hearing aid is divided into a BTE part adapted to be located at or behind the user's ear (pinna) and an ITE part adapted to be located in or at the user's ear canal. As shown in Figure 3A , the BTE part includes two microphones (M BTE1 and M BTE2 ) and the ITE part includes one microphone M ITE . The ITE part includes an ear mold forming the housing, and the microphone M ITE and the speaker SPK are located therein. The ear mold is adapted to the user's ear canal, for example, to minimize sound leakage from the speaker SPK of the hearing aid to the environment (and from the environment to the eardrum). The ear mold may include a vent to equalize the pressure between the environment and the residual cavity between the ear mold and the eardrum (thereby minimizing the occlusion effect). The ear mold may include a sensor S ITE located near the surface of the housing, enabling contact with or interaction with the tissue of the ear canal. The sensor may be, for example, a potential sensor (e.g., picking up signals from the brain (such as EEG) or / and from the eyeball (such as EOG) or from muscle contractions (such as jaw movement), or a motion sensor, such as picking up vibrations of the skin or bone (e.g., detecting when the user is speaking) (self-voice)), or an EPF sensor picking up light reflection from the ear canal, or a temperature sensor for estimating temperature, or a photoplethysmogram (PPG) sensor for estimating multiple different characteristics of the user's body (such as heart rate), etc.

[0125] According to the present invention, as described in connection with Figure 1 , 2A , 2B, three microphone signals (see Figure 2A , 2B for IN BTE1 , IN BTE2 , IN ITE ) are transmitted to the beamformer filter BFU and used to provide one or more beamformed signals Y BF, and is further processed in a signal processor DSP including a controller CTR and a processor HLC. A signal S from one or more sensors ITE is transmitted to the signal processor DSP and is considered there (e.g., processed and / or passed to another device, such as a user interface for processing and / or presentation there). One or more other sensors connected to the hearing aid may be located in the BTE portion or elsewhere at or around the user's ear (or implanted in the user's head or body).

[0126] The hearing aid HD, e.g., the BTE portion and / or the ITE portion, may include a (wireless or wired) programming interface and possibly a (wireless or wired) user communication interface. The programming interface (enabling connection to a programming device such as a fitting system) and the user communication interface may be implemented using Figure 3A one or two wireless transceivers (WLR1, WLR2) located in the BTE portion as shown. As an alternative, these interfaces may be implemented as a wired connection, e.g., via a connector.

[0127] The connecting element IC between the BTE portion and the ITE portion is shown as a cable, which includes electrical conductors for electrically connecting the electronic components (and battery BAT) of the BTE portion and the ITE portion. The connecting element includes a connector to the BTE portion, enabling the ITE portion (and the connecting element) to be easily separated from and connected to the BTE portion (and e.g., enabling exchange with another element, such as including different speakers or different sensors, or without a microphone, or more than one microphone, etc.). When the speaker is located in the BTE portion rather than the ITE portion, the connecting element IC between the BTE portion and the ITE portion may include an acoustic tube.

[0128] The BTE portion includes a substrate SUB, which includes electronic components (a memory MEM, a front-end IC (FE), and a digital signal processor IC / DSP) and appropriate wiring Wx for interconnecting the electronic components on the substrate and connecting to the battery BAT, the wireless transceivers (WLR1, WLR2), the microphones (M BTE1 , M BTE2 , M ITE ), the sensors S ITE , the speaker SPK, and other components of the BTE and ITE portions. The memory MEM may store appropriate settings of the hearing aid, such as different hearing aid programs and customization parameters. The front-end IC (FE) is an integrated circuit that processes the interfaces mainly to analog components such as microphones and speakers and possibly sensors, etc. The digital signal processor DSP includes the digital components of the hearing aid, which include a beamformer filter BFU, a controller CTR, a processor HLC, etc., as described in connection with Figure 1 , 2A , 2B.

[0129] The microphone of the hearing aid is configured to pick up sound elements of the sound field S around the hearing aid HD (i.e., around the user wearing the hearing aid), (BTE microphone (M BTE1 , M BTE2 ) of S BTE and ITE microphone M ITE ) of S ITE ). The sound field S at the eardrum of the user wearing the hearing aid ED is the result of the sound generated by the speaker SPK and the sound leaking into the ear canal from the environment of the ITE part of the hearing aid (e.g., through vents or other openings). According to the present invention, the sound transmitted by the speaker is determined based on the user's auditory ability (such as hearing loss, i.e., the appropriate gain applied to the hearing aid), the sound fields picked up by the microphones (S BTE , S ITE ), and the current feedback estimation from the speaker SPK to the corresponding microphones (M BTE1 , M BTE2 , and M ITE ).

[0130] Figure 3B Another embodiment of the hearing aid HD according to the present invention is shown. Figure 3B An ITE-type hearing aid according to an embodiment of the present invention is schematically shown. The hearing aid HD includes or consists of an ITE part, which includes a housing, which can be a standard housing aimed at fitting a group of users, or can be customized for the user's ear (e.g., as an ear mold, e.g., providing a proper fit with the outer ear and / or ear canal). Figure 3B The housing schematically shown in has a symmetric shape, e.g., around a longitudinal axis (when installed) from the environment towards the user's eardrum, but this is not necessary. It can be customized for the shape of the ear canal of a specific user. The hearing aid can be configured to be located in the outer part of the ear canal, e.g., visible from the outside part; or it can be configured to be completely located in the ear canal, possibly deep into the ear canal, e.g., completely or partially in the bony part of the ear canal.

[0131] To minimize the sound leaking from the ear canal (played by the hearing aid towards the user's eardrum), good mechanical contact between the hearing aid housing and the skin / tissue of the ear canal is required. When attempting to minimize the aforementioned leakage, the housing of the ITE part can be customized for the specific user's ear.

[0132] The hearing aid HD includes Q microphones M q, i=1,…,Q, here two (Q=2). Two microphones (M1, M2) are located in the housing with a predetermined distance d such as 8-10 mm between them, for example, on a part of the surface of the housing facing the environment when the hearing aid is mounted in or at the ear of the user. The microphones (M1, M2) are, for example, located on the housing so that when the hearing aid is mounted in or at the ear of the user, their microphone axes (axes passing through the centers of the two microphones) point in a forward direction relative to the user, for example, the user's viewing direction (e.g. determined by the user's nose, for example, substantially in a horizontal plane). The two microphones are thus well suited for generating directional signals toward the front (and / or behind) of the user. The microphones are configured to convert sounds (S1, S2) received from a sound field S around the user at their respective positions into corresponding (analog) electrical signals (s1, s2) representing the sounds. The microphones are connected to corresponding analog-to-digital converters AD to provide the corresponding (analog) electrical signals (s1, s2) as digitized signals (s1, s2). The digitized signal can be further connected to a corresponding filter bank to provide each electrical input signal (time domain signal) as a sub-band signal (frequency domain signal). The (digitized) electrical input signal (s1, s2) is fed to a digital signal processor DSP for processing the audio signal (s1, s2), for example including one or more of the following: spatial filtering (beamforming), (such as single-channel) noise reduction, compression (amplification / attenuation that varies with frequency and level according to the needs of the user, such as hearing loss), spatial cue preservation / restoration, etc. The digital signal processor DSP may, for example, include appropriate filter banks (such as analysis and synthesis filter banks) to enable frequency domain processing (individual processing of sub-band signals). The digital signal processor DSP is configured to provide the processed signal s1, s2. out , which includes a representation of the sound field S (e.g., including an estimate of the target signal therein). The processed signal s out is fed to an output transducer (here the loudspeaker SPK), for example via a digital-to-analog converter DA, for converting the processed (digital electrical) signal s out (or simulated versions out ) is converted into a sound signal S out In an operating mode according to the invention (depending on the current feedback path estimate), the hearing aid is configured to use A) a spatially filtered signal (from a beamformer filter, see e.g. Figure 1 IN BF and BFU) or B) a specific electrical input signal among the electrical input signals (s1, s2) (or a processed version thereof such as a feedback-corrected version) is processed by a processor (e.g. according to the needs of the user) and presented to the user via a speaker SPK (possibly via a DA converter DA).

[0133] The hearing aid HD may for example comprise a ventilation channel (vent) configured to minimize the occlusion effect (when the user is speaking). In addition to enabling the creation of a residual cavity between the hearing aid housing and the eardrum (see Figure 3B ) of the (unplanned) acoustic propagation path S leak In addition, the ventilation channel provides a direct acoustic propagation path for sound from the environment to the residual cavity. The directly propagated sound S dir Mixed with the acoustic output of the hearing aid HD to produce a synthetic sound S at the eardrum ED In one operating mode, active noise suppression (ANS) is activated to attempt to cancel the directly transmitted sound S dir .

[0134] The hearing aid HD comprises a forward path, which comprises two (or more) input transducers (here two microphones (M1, M2)), a suitable AD converter AD, a digital signal processor DSP (for example comprising suitable analysis and synthesis filter banks, and optionally one or more for enhancing the input audio signal (s1, s2) to provide a processed signal s out The forward path is configured to pick up external sound, process the sound and output a processed version of the sound S out In addition to the external sound (S1, S2), the microphones (M1, M2) also receive (and pick up) other leakage paths (at the output transducer SPK of the hearing aid, e.g. via the vent and / or from the residual cavity at the eardrum to the respective microphones (M1, M2). Figure 3B The sound of leakage (S leak1 ,S leak2 ). By the sound of leakage (S leak1 ,S leak2 ) is estimated by the hearing aid via the feedback estimation unit FE, for example, see Figure 1 According to the present invention, for example, in combination Figure 1 As described, the resulting estimates (see, e.g., FBE1, FBE2) are used to control which input signal (s1 or s2) or the beamformed signal as a combination of the electrical input signals (s1, s2) is further processed and presented to the user at a given point in time. The ventilation channel (vent) is located asymmetrically in the hearing aid housing. Such an asymmetrical position may be the result of design constraints caused by hearing aid components such as a battery. The first and second microphones (M1, M2) thus have different feedback paths from the loudspeaker SPK. The first microphone M1 is closer to the ventilation channel than the second microphone M2. Under other conditions being the same, the feedback measure FBM1 of the first microphone is greater than the feedback measure FBM2 of the second microphone, at least above a minimum frequency, see, e.g.,Figure 4B A scheme according to the present invention for controlling the use (such as switching, e.g., ramping therebetween) of a beamforming signal or a signal from a single input transducer in the forward path of a hearing aid can be applied to Figure 3B ITE hearing aids such that the positioning of the input transducer and the vent passage relative to each other is more flexible without compromising (reducing) the full-on gain value of the hearing aid. When the microphone system of the hearing aid is in the DIR mode (where the beamforming signal is used for amplification and presentation to the user) and when the feedback of one of the microphones (or the feedback path difference measure of both microphones) increases above a threshold level, the mode of the microphone system changes to the OMNI mode. In the OMNI mode, the signal from the (single) microphone with the lowest feedback is used for amplification and presentation to the user. Thus, feedback howling at the current feedback level can be avoided.

[0135] The hearing aid includes an energy source such as a battery BAT, e.g., a rechargeable battery, for powering the components of the hearing device.

[0136] Figure 4A A relationship curve between the mechanical feedback measure (M-FB) of the hearing aid and frequency is shown, where the full-on gain parameter (FOG) is illustrated; and Figure 4B Schematically shows the relationship between exemplary first and second feedback measures (FBM) and frequency.

[0137] Figure 4A Shows how the (mechanical) feedback measure M-FB [dB] varies with frequency f [Hz] (possibly on a logarithmic scale) under full-on gain conditions (e.g., ANSI S3.22-2003: Specification of Hearing Aid Characteristics) and the specific frequency range (between the first and second threshold frequencies f TH1 , f TH2 determines the maximum full-on gain (FOG). The maximum full-on gain of a super-power BTE hearing aid (such as Figure 3A ) can be, for example, in the range between 60 dB and 90 dB, e.g., ≤87 dB, and for the corresponding ITE hearing aid (e.g., Figure 3B ), in the range between 40 dB and 70 dB. The specific frequency range that determines the maximum allowable FOG (i.e., exhibiting the maximum mechanical feedback) depends on the specific hardware configuration, but for a typical BTE super-power hearing aid, it can be in the range between 800 - 1000 Hz, e.g., having the maximum feedback at 900 Hz, and for the corresponding ITE hearing aid, approximately 3 kHz (as Figure 4A marked by f max ). Figure 4A Shows a hearing aid according to the present invention (e.g., such asFigure 3B exemplary operating modes (see the "Mode" label and the three arrows pointing to three frequency ranges, and the three different operating modes as shown in TH1 ). At low frequencies (below f Figure 1 ), the directional system of the hearing aid (e.g., see the BFU in Figure 4A ) is in the omnidirectional mode (denoted as "Enhanced OMNI" in Figure 1 and implemented, for example, by a delay-and-sum beamformer), so that in the frequency band covering this frequency, the resulting beamformed signal is used for further processing (amplification, etc.) in the processor ( TH2 ). At high frequencies (above f Figure 1 ), the directional system of the hearing aid is in the directional mode, implemented, for example, by a delay-and-subtract beamformer, so that in the frequency band covering this frequency, the resulting beamformed signal is used for further processing in the processor ( TH1 ). In the frequency band covering the intermediate frequency range (above f TH2 ), one of the input signals (e.g., IN1 or IN2 in Figure 1 , or s1 or s2 in Figure 3B ) is selected for further processing in the processor (so that the beamformed signal is not used in the intermediate range).

[0138] Figure 4B shows examples of different (acoustic) feedback paths from the output transducer to the corresponding (first and second) input transducers, such as the input transducers M1 and M2 shown in Figure 3B . The feedback path is represented by the relationship between the feedback gain (attenuation, e.g., represented by a negative gain value in dB) FBG[dB] and the frequency f[Hz] (e.g., on a logarithmic scale, or as the FBG value at preselected discrete frequencies). The feedback gain of the hearing aid depends on the type, including the relative positions of the microphone and the speaker. In a (very) general case, the feedback typically decreases with frequency from about 1 kHz to 10 kHz. However, there may be multiple large peaks and valleys in this frequency range that deviate locally from this trend. Figure 4B The two FBG curves of

[0139] indicate this general trend. The first feedback metric FBM1 of the first microphone M1 (here the feedback gain FBG) is typically greater than the second feedback metric FBM2 of the second microphone M2 (less negative). The feedback path difference metric FBDM 12 can be defined as the difference between the first and second feedback metrics (such as the feedback path estimators), FBDM 12 = FBM1 - FBM2. The feedback path difference metric FBDM 12It can be determined at multiple specific frequencies, for example, at the center frequencies of all (or selected) frequency bands or at a finite number of frequency bands such as 500 Hz, 1 kHz, 2 kHz, 4 kHz, 8 kHz. According to the present invention, in the critical feedback operating mode, the distance metric FBDM determined at one or more of these frequencies can be used to control the input signal (determine its selection) of the hearing aid processor, for example, when a specific feedback criterion is satisfied (such as loop gain ≤ LG max ). In the example of Figure 4B , the minimum gain margins GM (GM1, GM2) of two microphones (M1, M2) (for example, at the 10 - 20 dB level) are marked near the frequency f1, corresponding to maximum feedback gains of -12 dB and -20 dB respectively.

[0140] As described in connection with Figure 4A , the hearing aid can be in different operating modes in different frequency bands (or frequency ranges) according to the value of the feedback path difference metric in each frequency band (or frequency range). The (resulting) feedback path difference metric FBDM(Δf) of a given frequency range Δf can be determined, for example, as the average (such as a weighted average) of the feedback path difference metrics at multiple frequencies in the involved range. The first and second feedback metrics or the (resulting) feedback path difference metric can be averaged over a certain time period, for example, on the order of several seconds.

[0141] When appropriately replaced by corresponding processes, the structural features of the devices described above, detailed in the "Detailed Description" and defined in the claims, can be combined with the steps of the method of the present invention.

[0142] Unless explicitly stated otherwise, the singular forms "a", "the" used herein are intended to include the plural forms (i.e., having the meaning of "at least one"). It should be further understood that the terms "having", "including", and / or "comprising" used in the specification indicate the presence of the 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 combinations thereof. It should be understood that unless explicitly stated otherwise, when an element is referred to as "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there can be intervening elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed related items. Unless explicitly stated otherwise, the steps of any method disclosed herein do not have to be performed in the exact order disclosed.

[0143] It should be appreciated that when the specification states "an embodiment" or "embodiments" or "aspect" or "may" include a feature, it means that the particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the present invention. Further, the particular features, structures, or characteristics may be appropriately combined in one or more embodiments of the present invention. The foregoing description is provided to enable those skilled in the art to practice the various aspects described herein. Various modifications will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects.

[0144] The claims are not limited to the aspects shown herein, but encompass the full scope consistent with the claim language, where elements recited in the singular are not meant to mean "one and only one" unless explicitly stated otherwise, but rather "one or more". Unless explicitly stated otherwise, the term "some" means one or more.

[0145] Accordingly, the scope of the present invention should be determined in accordance with the claims.

[0146] References

[0147] ·EP3185589A1 (Oticon) 28.06.2017.

[0148] · [Brandstein & Ward; 2001] M. Brandstein and D. Ward, "Microphone Arrays", Springer 2001.

[0149] ·EP3229490A1 (Oticon) 11.10.2017.

[0150] ·EP3185588A1 (Oticon) 28.06.2017.

Claims

1. A hearing aid adapted to be located at or in a user's ear and adapted to compensate for the user's hearing loss, the hearing aid comprising: - A forward path, comprising -- At least two input transducers, each input transducer for picking up sound from the hearing aid environment and providing a corresponding at least two electrical input signals; -- A beamformer filter for filtering the at least two electrical input signals and providing a spatially filtered signal; -- A signal processor for processing one or more of the electrical input signals and providing one or more processed signals on the basis of the processing; And -- An output transducer for generating a stimulus perceptible as sound by the user based on one or more processed signals; And - A feedback estimation system for estimating the current feedback from the output transducer to each of the at least two input transducers and providing a corresponding feedback metric indicative of the feedback; - A controller configured to receive the feedback metric from the feedback estimation system; wherein the controller is configured to switch between two operating modes of the hearing aid, namely an omnidirectional operating mode and a directional operating mode, according to the feedback metric; wherein the hearing aid comprises an ITE part adapted to be located at or in the user's ear canal, wherein the ITE part comprises the at least two input transducers and the output transducer; wherein the controller is configured to switch to the omnidirectional operating mode when the current feedback path difference metric between two of the feedback metrics is greater than a first threshold, and to select the electrical input signal from the input transducer having the smallest feedback metric among the at least two input transducers as the input signal to the signal processor; wherein the controller is configured to switch to the directional operating mode when the feedback path difference metric between each feedback metric is less than a second threshold, and to select the spatially filtered signal as the input signal to the signal processor.

2. The hearing aid according to claim 1, wherein the feedback metric for a given input transducer comprises the impulse response of the feedback path from the output transducer to the input transducer in question, or the frequency response of the feedback path from the output transducer to the input transducer in question, the latter being measured at a plurality of frequencies.

3. The hearing aid according to claim 1, wherein the at least two input transducers are positioned asymmetrically relative to the output transducer.

4. The hearing aid according to claim 1, comprising a BTE part adapted to be located at or behind the user's ear, wherein the BTE part and the ITE part are electrically or acoustically connected to each other.

5. The hearing aid according to claim 1, wherein the ITE part comprises a ventilation channel or other open structure to enable air exchange between the cavity near the eardrum and the environment when the ITE part is mounted at or in the user's ear canal.

6. The hearing aid according to claim 5, wherein the at least two input transducers are positioned asymmetrically relative to the ventilation channel or other open structure.

7. The hearing aid according to claim 1, wherein the beamformer filter is configured to provide the spatially filtered signal as corresponding sub-band signals.

8. The hearing aid according to claim 7, wherein the beamformer filter is configured to individually set an omnidirectional or a directional mode in corresponding sub-bands.

9. The hearing aid according to claim 7, wherein the controller is configured to individually select, for different frequency ranges, one of the spatially filtered signal or the electrical input signal as the input signal to the signal processor, based on the sub-band signals and the feedback criterion.

10. The hearing aid according to claim 1, wherein the feedback metric indicates acoustic feedback or mechanical feedback.

11. A method of operating a hearing aid, the hearing aid being adapted to be located at or in a user's ear and being adapted to compensate for the user's hearing loss, the method comprising: - providing at least two electrical input signals representing sounds picked up from the hearing aid environment by corresponding at least two input transducers; - providing a spatially filtered signal based on the at least two electrical input signals; - processing one or more of the electrical input signals and providing one or more processed signals based thereon; - generating, based on the one or more processed signals, a stimulus for an output transducer that can be perceived as sound by the user; - estimating a current feedback from the output transducer to each of the at least two input transducers and providing a corresponding feedback metric indicating the feedback; - switching between two operating modes of the hearing aid, namely an omnidirectional operating mode and a directional operating mode, according to the feedback metric; wherein the hearing aid includes an ITE portion adapted to be located at or in the user's ear canal, and wherein the ITE portion includes the at least two input transducers and the output transducer; wherein switching between the two operating modes of the hearing aid includes: - switching to the omnidirectional operating mode when a current feedback path difference metric between two of the feedback metrics is greater than a first threshold, and selecting as the input signal to the signal processor the electrical input signal from the input transducer having the smallest feedback metric among the at least two input transducers; - switching to the directional operating mode when the feedback path difference metric between each feedback metric is less than a second threshold, and selecting the spatially filtered signal as the input signal to the signal processor.

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