Method for operating a hearing aid

Abstract

The invention relates to a method for operating a hearing aid (2), wherein a first input signal (32) is generated from an ambient sound signal by a first input transducer (30) of the hearing aid (2), wherein an external input signal (36) is generated from the ambient sound signal by an external input transducer (34) outside the hearing aid (2), wherein a relative transfer function of the external input transducer (34) to the hearing aid (2) with respect to a target signal source (4) is determined on the basis of the first input signal (32) and the external input signal (36), and the external input signal (36) is filtered with the relative transfer function, thereby generating an estimated target signal (42), and wherein noise suppression in the hearing aid (2) takes place on the basis of the estimated target signal (42).The invention further mentions a hearing aid system, comprising a hearing aid (2) with at least one first input transducer (30) for generating a first input signal (32), - an external input transducer (34) for generating an external input signal (36) and a processor unit which is designed to carry out such a method.

Description

[0001] The invention relates to a method for operating a hearing aid, wherein a first input signal is generated from a sound signal of the environment by a first input transducer of the hearing aid, wherein an external input signal is generated from the sound signal of the environment by an external input transducer outside the hearing aid, and wherein noise suppression in the hearing aid takes place on the basis of the external input signal.

[0002] The use of external input signals for noise suppression in hearing aids has gained importance, particularly due to the increasing availability of such external input signals. Due to the increasing prevalence of mobile phones that provide external input signals via a mobile phone microphone, as well as the mobile phone's ability to transmit the external input signal to a hearing aid, a hearing aid wearer can obtain improved sound quality from the output sound signal generated by the hearing aid, particularly in conversation situations where background noise obscures the conversational contributions of a conversation partner.

[0003] To date, the use of the external input signal to estimate the useful or target signal contributions of a conversation partner and to distinguish them from noise has been particularly relevant. This occurs, for example, under the assumption that the mobile phone is positioned in front of the hearing aid wearer's body and thus somewhat closer to a conversation partner in front of them than the hearing aid, whereby the hearing aid has a slightly improved signal-to-noise ratio (SNR) for a useful signal in front of them compared to an input signal generated in the hearing aid itself. This makes it possible, for example, to detect the periods in which the conversation partner standing in front of the hearing aid wearer is speaking. The actual signal processing then takes place on the input signals of the hearing aid with knowledge of these periods.

[0004] The use of signal components of an external input signal to generate an output signal in a hearing aid in the sense that the signal components only experience frequency band-dependent amplification and / or compression, but otherwise enter directly into the output signal, has not been feasible to date due to the difficulty of determining the relative positioning of the mobile phone to the conversation partner and the resulting problems of spatial hearing.

[0005] US 2018 / 0 054 683 A1 discloses a hearing system comprising a binaural hearing aid and an external microphone unit, which is worn by the user of the system on a carrying strap around the neck. The microphone unit can be controlled via voice commands from the user, for example, to set operating programs of the binaural hearing aid as a remote control. For noise suppression of the sound signals arriving at the microphone unit, the relative transfer function from the user to a reference microphone of the microphone unit can be used, among other things. The noise-suppressed speech signal from the user of the hearing system can then be transmitted, for example, to a mobile phone or similar device.

[0006] A similar hearing system is disclosed in US 2016 / 0 241 975 A1. However, in this case, the external microphone unit is worn by a conversation partner of the hearing system user in order to provide the user with a particularly low-noise speech signal from the conversation partner. Noise suppression for the speech signal can be achieved in a similar manner to that disclosed in US 2018 / 0 054 683 A1. The noise-suppressed speech signal of the conversation partner can then be transmitted from the external microphone unit to the binaural hearing aid or to a receiver unit worn by the user, which is in data communication with the binaural hearing aid.

[0007] EP 3 373 603 A1 describes a hearing aid comprising a plurality of input units providing corresponding electrical input signals, each of which includes an audio signal from an audio signal source and acoustic signals from other acoustic signal sources in the vicinity of the hearing aid, as received at the respective input unit. The hearing aid further comprises a wireless receiver for receiving and providing a direct representation of the audio signal, as well as a directional microphone filter unit configured to receive the plurality of electrical input signals and generate a directional signal therefrom.The hearing aid further comprises a combination unit for providing a mixed signal comprising a combination of the direct representation of the audio signal and the directional signal or signals derived therefrom, and further comprises an output unit which outputs a sound signal to a user based on the mixed signal.

[0008] US 2016 / 0 192 090 A1 discloses a method for superimposing spatial auditory information ("spatial cues") with an externally recorded sound signal in a hearing aid. The method comprises the steps of: generating an external microphone signal by an external microphone arrangement and transmitting the external microphone signal to a wireless receiver of a first hearing aid via a first wireless communication connection; determining the response characteristics of a first spatial synthesis filter by correlating the external microphone signal and a first hearing aid microphone signal of the first hearing aid; and filtering the external microphone signal through the first spatial synthesis filter to generate a first synthesized microphone signal comprising first spatial auditory information.

[0009] The invention is therefore based on the object of providing a method for operating a hearing aid in which the sound quality is improved by means of an external input signal. The invention is further based on the object of providing a hearing aid system with an external input transducer by means of which such a method can be implemented.

[0010] The first-mentioned object is achieved according to the invention by a method for operating a hearing aid, wherein a first input signal is generated from an ambient sound signal by a first input transducer of the hearing aid, wherein an external input signal is generated from the ambient sound signal by an external input transducer outside the hearing aid, wherein a relative transfer function of the external input transducer to the hearing aid with respect to a target signal source is determined based on the first input signal and the external input signal, and the external input signal is filtered with the relative transfer function, thereby generating an estimated target signal, and wherein noise suppression in the hearing aid takes place based on the estimated target signal. Advantageous and partly inventive embodiments are the subject of the dependent claims and the following description.

[0011] An input transducer in this case particularly includes an acoustoelectrical transducer, e.g. as at least one microphone. The external input transducer is not included in the hearing aid but is spatially separated from it and is particularly arranged in a housing. The external input transducer is preferably arranged in a higher-level device which is delimited by the housing, e.g. a mobile phone, or in particular in an additional external unit which is specifically designed and intended for use together with the hearing aid but is not worn on the ear and is also only optional for the intended operation of the hearing aid and is therefore not part of the hearing aid as such.

[0012] To implement the method, the external input signal can be transmitted from the higher-level device to the hearing aid, so that the individual process steps are performed in the hearing aid. Alternatively, the first input signal can be transmitted to the higher-level device of the external input converter, so that parts of the method are performed in the higher-level device, and, for example, the estimated target signal is transmitted to the hearing aid for further processing.

[0013] The relative transfer function of two input signals x1(n), x2(n) generated at different locations with respect to a sound source S is defined in the discrete frequency domain as the quotient of the two transfer functions H S1 (k), H S2 (k) from the sound source to the respective generation location of the input signal, i.e. in the frequency domain: X1(k)=HS1(k)⋅S(k), X2(k)=HS2(k)⋅S(k), X1(k)=H21|S(k)⋅X2(k) with the relative transfer function H 21|S (k) = H S1 (k) / H S2 (k) with respect to S, where X j (k) the x j (n) is the corresponding signal in the frequency domain, and S(k) denotes the signal generated by the source S (in the frequency domain). This takes into account, in particular, an acoustic delay between the two generation locations and thus a phase difference between the two input signals occurring in the frequency domain.

[0014] By filtering the external input signal with the relative transfer function of the external input transducer to the hearing aid with respect to a target signal source, the estimated target signal, in the hypothetical ideal case of a perfect determination of the relative transfer function, corresponds exactly to the sound signal arriving at the hearing aid from the direction of the target signal source. However, deviations in the determination of the relative transfer function can be minimized using appropriate measures, so that the estimated target signal essentially contains the signal components of a target signal generated by the target signal source. This knowledge can then be used for noise suppression.

[0015] In this case, it can also be exploited that the wearer of the hearing aid can freely choose the position of the external input transducer in particular in order to position it favorably with respect to the target signal source, e.g. in front of his body, whereby on the one hand a higher signal amplitude of the target signal can be achieved as a result of the greater spatial proximity compared to diffuse background noise, and on the other hand the shielding effect of the wearer's body also contributes to improving the SNR in the external input signal against directed noise which is generated away from the direction of the target signal source.

[0016] According to the invention, noise suppression is achieved using an estimated noise signal, which is generated using the estimated target signal and the first input signal. The information contained in the estimated target signal regarding the signal components of the target signal can be used to determine an estimated noise signal containing information about the noise component by comparing it with other existing signals, which, due to their generation and possibly further processing, also have a high target signal component. Noise suppression based on the estimated noise signal can then be achieved, for example, by determining a spectral noise power density, which is used to determine frequency-band-specific weighting coefficients for processing the first input signal in the hearing aid.

[0017] In particular, this can take advantage of the fact that the external input signal already has a better SNR than the first input signal due to favorable positioning of the external input transducer or its higher-level device with respect to the target signal source. Conventional methods for noise suppression in a hearing aid determine the noise component during pauses between speech contributions from a conversation partner. However, such an approach is no longer possible, especially in the case of directional background noise, such as that which may be present in speech contributions from a speaker positioned substantially behind the wearer, as noise suppression can lead to significant errors and artifacts in the output signal.The present method avoids these problems because, unlike the first input transducer of the hearing aid, the external input transducer can be positioned in such a way that such noise is not falsely interpreted as a “useful signal” due to its non-stationarity.

[0018] According to the invention, the estimated target signal, which represents the signal components of the target signal of the target signal source, is subtracted from the first input signal or from a first intermediate signal derived from the first input signal, wherein the first intermediate signal is particularly preferably constructed in such a way that it has at least the same proportion of target signal as the first input signal, or has at least the same SNR. Assuming that the useful signal component in the first input signal largely originates from the target signal, subtracting the estimated target signal from the first intermediate signal, particularly in the case mentioned, provides an estimated noise signal which, on the one hand, is meaningful for noise suppression during generation of the first intermediate signal, but on the other hand is also meaningful for the quality of the estimated target signal and thus the estimation of the relative transfer function.

[0019] The first intermediate signal can be generated, in particular, from the first input signal by applying frequency-band-specific noise suppression, whereby the attenuation factors of the individual frequency bands can be determined, for example, using statistical models and / or based on spectral power densities. According to the invention, the first intermediate signal is a first noise-suppressed signal, from which the estimated target signal is subtracted to generate the first noise signal.

[0020] According to the invention, the relative transfer function is generated from the external input signal by means of an adaptive filter into which the estimated noise signal is input as an error signal and in which the external input signal is also filtered, so that the output signal of the adaptive filter is preferably the estimated target signal. Advantageously, this can take advantage of the fact that, in particular, a first noise-suppressed signal as the first intermediate signal should have only a low noise component and, in particular, a high SNR, so that subtraction of the estimated target signal output by the adaptive filter should largely cancel out the signal components of the target signal in the first intermediate signal, and the remaining noise, which is represented by the estimated noise signal thus generated, provides a meaningful measure of the quality of the adaptation to the relative transfer function.

[0021] Preferably, the step size of the adaptive filter is controlled as a function of the external input signal of the first input signal. This can be achieved, for example, by determining a probability for the occurrence of certain signals, with respect to which the noise suppression is to be optimized, based on the external input signal and / or the first input signal, and controlling the step size as a function of this probability. In particular, such a signal, with respect to which the noise suppression is to be optimized, can be a target signal from the frontal direction.

[0022] Advantageously, a second input transducer of the hearing aid generates a second input signal from the ambient sound signal, and the relative transfer function of the external input transducer to the hearing aid with respect to a target signal source is determined based on the first input signal and / or the second input signal and / or the external input signal. This provides additional spatial information from the external input signal, which can be used, particularly when forming directional signals based on the first input signal and the second input signal, to reduce undesirable remaining symmetries in a directional characteristic of the corresponding directional signal, particularly with respect to the wearer's frontal plane.

[0023] The first input signal and the second input signal are preferably each generated in two different local devices of a binaural hearing aid, so that one of these two input signals is generated on the left side of the wearer's head, and the other input signal is generated on the right side of the head. However, these two input signals can also both be generated in a monaural hearing aid that the wearer wears in one ear.

[0024] The relative transfer function is determined, in particular, by generating a first directional signal based on the first input signal and the second input signal, and by determining the relative transfer function of the external input transducer to the hearing aid with respect to the target signal source based on the first directional signal and the external input signal. In this case, the first directional signal can be generated, in particular, such that, as a result of the directional effect, noise is suppressed in a frequency band-wise or broadband manner, so that the first directional signal forms an embodiment of the first noise-suppressed signal and thus a special embodiment of the first intermediate signal.

[0025] Preferably, the estimated noise signal is formed by subtracting the estimated target signal from the first directional signal. Due to the noise suppression, particularly of diffuse noise, that occurs during the formation of the first directional signal, the first directional signal already exhibits an improved SNR compared to the two input signals used. This subtraction now allows a statement to be made about the quality of the estimation of the relative transfer function from the determined deviation of the estimated target signal component from the first directional signal, particularly in the case where a target signal component is present in the input signals involved.

[0026] The said procedure is in particular combined with an adaptive filter for determining the relative transfer function and in particular for generating the estimated target signal from the external input signal, wherein the noise signal preferably estimated from the first directional signal and the estimated target signal is input into the adaptive filter as an error signal.

[0027] The step size of the adaptive filter can be controlled in particular as a function of the probability of a frontal target signal source, which is preferably determined using the external input signal as well as the first input signal and / or the second input signal. Adaptation with a large step size is preferably carried out when the probability of a target signal from the frontal direction is high. In this case, the estimated noise signal is particularly informative for the quality of the adaptation of the adaptive filter due to the high target signal component in the input signals involved. One possibility for determining this probability is described in Dianna Yee, A. Homayoun Kamkar-Parsi, Rainer Martin, Henning Puder, “A Noise Reduction Postfilter for Binaurally Linked Single-Microphone Hearing Aids Utilizing a Nearby External Microphone”, IEEE / ACM Trans. Audio, Speech & Language Processing 26(1). pp.5-18, 2018.

[0028] On the one hand, noise suppression can be achieved by determining a noise suppression parameter based on the estimated noise signal, which is then applied to a second intermediate signal derived from the first input signal. An output signal is generated based on the noise-suppressed second intermediate signal, and an output sound signal is generated from the output signal by an output transducer of the hearing aid. This means, in particular, that the estimated noise signal is used, for example, to determine frequency-band-dependent parameters such as gain factors or, in the case of a directional signal as the second intermediate signal, parameters relating to the directivity, without the signal components of the external input signal being directly incorporated into the output signal.In particular, the first intermediate signal and the second intermediate signal can be identical to each other, or they can be different in terms of their signal components. In particular, the second intermediate signal can also be provided by the first directional signal.

[0029] On the other hand, a second directional signal can also be generated based on the estimated target signal and the first input signal. The output signal is generated based on the second directional signal, and an output sound signal is generated from the output signal by an output transducer of the hearing aid. This means that the signal components of the external input signal are now incorporated into the output signal. Here, the filtering of the external input signal with the relative transfer function is again advantageously utilized, which in particular means an adjustment of a phase difference resulting from a difference in the propagation time of the target signal to the external input transducer or to the first and second input transducers.When forming a directional signal based on the external input signal with the hearing aid input signal, it is precisely this phase difference, due to the inaccurate positioning of the external input transducer relative to the hearing aid, that is usually an obstacle. This is eliminated by "filtering out" this phase difference using the relative transfer function. This is particularly advantageous for binaural hearing aids, in which the first and second input signals are each generated in different local devices of the binaural hearing aid, since the two local devices already define a preferred plane or direction in space, with respect to which a directional signal generated with the signal components of the external input signal must be aligned.

[0030] The second directional signal or a signal derived therefrom or a second intermediate signal derived from the first input signal and / or the second input signal to generate the second directional signal can additionally be subjected to noise suppression, the parameters of which are determined in the manner described above using the estimated noise signal. Preferably, the estimated target signal can also be additionally subjected to noise suppression, in particular single-channel noise suppression, before the formation of the second directional signal. Preferably, possible volume differences between the estimated target signal and the second intermediate signal or the noise-suppressed second intermediate signal, which may occur due to the greater proximity of the external input transducer to the target signal source and / or due to different sensitivities of the input transducers involved, are compensated for before the formation of the second directional signal.

[0031] The second object is achieved according to the invention by a hearing aid system comprising a hearing aid with at least one first input transducer for generating a first input signal from an ambient sound signal, an external input transducer for generating an external input signal from the ambient sound signal, and a processor unit configured to carry out the method described above. The advantages stated for the method and its further developments can be applied, mutis mutandis and vice versa, to the hearing aid system.

[0032] The hearing aid system can in particular comprise a second input transducer for generating a second input signal from the ambient sound signal. This can be arranged together with the first input transducer in a local device, or the two input transducers are each arranged in different local devices of a binaural hearing aid, so that the two input signals are generated on different sides of the wearer's head. The external input transducer and the processor unit can in particular be arranged in a common housing, wherein additional means for transmitting the relevant signals between the hearing aid and the processor unit are preferably also present in the housing. This can preferably be provided by a mobile phone, wherein the means for transmission can in particular be provided by Bluetooth.

[0033] An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. The drawings schematically show: Fig. 1 a hearing aid wearer in a conversation situation with a frontal conversation partner and another speaker, Fig. 2 a method for noise suppression in a monaural hearing aid using an external microphone, and Fig. 3 a design of the procedure according to Fig. 2 in a binaural hearing aid.

[0034] Corresponding parts and sizes are provided with the same reference numerals in all figures.

[0035] In Fig. Figure 1 schematically shows a top view of a wearer 1 of a hearing aid 2 who is engaged in a conversation with a conversation partner 4 positioned in front of the wearer, who constitutes the target signal source in this conversation. The hearing aid 2 is configured as a binaural hearing aid with corresponding local devices 6, 8, which are worn by the wearer 1 on the left and right sides of their head 10, respectively. However, the fundamental considerations within the scope of the invention also remain valid for a monaural design of the hearing aid 2.

[0036] The sound registered by the hearing aid 2 contains, on the one hand, the conversational contributions of the conversation partner 4 as a target signal 12, but on the other hand, it also contains noise components. These, in turn, can be divided into diffuse background noise, which cannot be assigned to a specific direction of origin, and a directional background noise 14, which in this case is provided by a conversational contribution from a speaker 18 positioned in the posterior hemisphere 16 of the wearer 1.

[0037] In order to be able to better emphasize the target signal 12 against the various noise components, in particular against the directed background noise 14, the hearing aid 2 accesses a microphone signal from a mobile phone 20 in a manner to be described below, wherein the wearer 1 wears the mobile phone 20 in front of his body 22, and the mobile phone is thus positioned somewhat closer to the frontal conversation partner 4 than the hearing aid 2. The noise suppression by means of the microphone signal from the mobile phone 20 in the hearing aid 2 essentially exploits the fact that the body 22 of the wearer 1 of the hearing aid 2 largely shields the mobile phone 20 from the directed background noise 14, and that the mobile phone 20 is also positioned somewhat closer to the frontal conversation partner 4 than the hearing aid 2 itself. Both of these lead to a somewhat improved SNR in the microphone signal of the mobile phone 20 compared to the signals generated by the hearing aid 2.

[0038] In Fig. 2 schematically shows a block diagram of a method for noise suppression in a hearing aid 2. The hearing aid 2 is designed as a monaural hearing aid with only one microphone as the first input transducer 30, which generates a first input signal 32 from the sound signals of the environment. For the suppression of noise in the first input signal 32, an external input transducer 34, such as can be provided, for example, by a microphone of the mobile phone 20 according to Fig. 1, an external input signal 36 is generated and transmitted to the hearing aid 2. The external input signal 36 is fed to an adaptive filter 40 in the hearing aid 2, in which a relative transfer function of the external input transducer 34 to the hearing aid 2 with respect to a Fig. 2 not shown in detail. The target signal source can be provided in particular by the conversation partner 4 positioned frontally to the wearer 1 according to Fig. 1.

[0039] By filtering the external input signal 36 with this relative transfer function, i.e. in particular by convolving the individual samples of the external input signal 36 in the time period with the corresponding coefficients of the impulse response of the relative transfer function, an estimated target signal 42 is generated. The construction of the relative transfer function with respect to the target signal source, which in the frequency domain is given by the quotient of the transfer function from the target signal source to the hearing aid with the transfer function from the target signal source to the external input transducer, the estimated target signal 42 ideally provides the acoustic information with respect to the target signal of the target signal source, which should be present at the first input transducer 30 of the hearing aid two, however, as a result of the Fig. 1 described shielding effect of the wearer's body adjusted for directed noise.

[0040] To calculate the relative transfer function, the adaptive filter 40 receives a corresponding error signal, which in this case is provided by an estimated noise signal 44. The estimated noise signal 44 is generated by subtracting the estimated target signal 42 generated by the adaptive filter 40 from a first intermediate signal 46. The first intermediate signal 46 is obtained from the first input signal 32 by preprocessing 48. The preprocessing 48 can, in particular, already include a step for frequency-band-wise noise suppression, so that the first intermediate signal 46 itself already forms a first noise-suppressed signal.By subtracting the estimated target signal 42 from the first intermediate signal 46, the resulting estimated noise signal 44 is, on the one hand, a quantitative measure of the remaining real signal noise and, on the other hand, also a measure of any misadaptation of the adaptive filter 40 to the real relative transfer function. Thus, the estimated noise signal 44 can be used as an error signal in the adaptive filter 40.

[0041] To control the adaptive filter, a control signal 50 can be generated based on the first input signal 32 and the external input signal 36, which control signal 50 directly influences the adaptive filter 40, for example by adjusting the step size in the adaptive filter 40. This can be done, for example, in such a way that the step size of the adaptive filter 40 only assumes a positive value as a result of the control signal 50 if the first input signal 32 and the external input signal 36 result in a sufficiently high probability of the presence of a target signal source, in particular in a predetermined direction.The information contained in the estimated noise signal 44 regarding noise components, particularly regarding directional background noise, can now be used to further suppress the noise component in the first input signal 32 or the first intermediate signal 46, and to use the resulting signal within the hearing aid 2 for further processing, in which an output signal is generated. However, the first input signal 32 or the first intermediate signal 46 can also be superimposed with the estimated target signal 42 to form a directional signal, thereby exploiting the additional noise-suppressing effect of the directional cone for remote noise sources.

[0042] In Fig. 3 is a schematic block diagram of another alternative of the method according to Fig. 2 for noise suppression in a hearing aid. The hearing aid is designed as a binaural hearing aid, which has a first input transducer 30 and a second input transducer 52. The first input transducer 30 and the second input transducer 52 are each arranged in different local devices 6, 8 of the hearing aid 2 according to Fig. 1. The signal processing steps described below can be carried out entirely in one of the two local devices 6, 8, or partially in a processor of the mobile phone 20, which includes the external input converter 34.

[0043] The first input signal 32, generated by the first input transducer 30, and a second input signal 54, generated by the second input transducer 52, are further processed in the preprocessing unit 48 to form a first directional signal 56. During the generation of the first directional signal 56 from the first input signal 32 and the second input signal 54, noise suppression, particularly frequency band-wise, can already be performed via the directional cone. This is preferably directed toward the target signal source, so that noises from other directions are already partially significantly suppressed. However, a directional characteristic of the first directional signal 56 typically exhibits a certain symmetry or a similar sensitivity with respect to the frontal plane of the wearer 1 of the hearing aid 2 without the use of further assumptions, which can make signal processing more complicated, computationally intensive, and thus slower.This has the consequence that also in the rear hemisphere 16 of the wearer 1 after . Fig. 1 a solid angle range exists in which a directional noise 14 is not sufficiently suppressed during the formation of the first directional signal 56.

[0044] In an approach similar to that used in Fig.2, the estimated target signal 42 is now generated from the external input signal 36 by means of the adaptive filter 40. The estimated noise signal 44, which is fed to the adaptive filter 40 as an error signal, is formed by subtracting the estimated target signal 42 from the first directional signal 56. This is done under the assumption that noise components, in particular those of a diffuse nature, are already suppressed in the first directional signal 56, so that the first directional signal 56 can be regarded as a first noise-suppressed signal, and thus the deviations from the estimated target signal 42 can be regarded as a measure of the adaptation or misadaptation of the adaptive filter 40 to the relative transfer function.

[0045] The control signal 50 for controlling the step size of the adaptive filter 40 is formed by calculating a probability 58 for the presence of a frontal target signal source based on the first input signal 32, the second input signal 54, and the external input signal 36. A spectral noise power density 60 can now be determined from the estimated noise signal 44. This can be done, in particular, by weighting the noise of the estimated noise signal 44 with the probability 58 for a frontal target signal source against the noise distribution of the first directional signal 56. From the spectral noise power density 60 thus determined, frequency band-wise weighting coefficients 62 can now be determined, which are to be applied to the first directional signal 56.From the noise-suppressed first directional signal 64 and the estimated target signal 42, a second directional signal 66 can now be generated, which has a further improved SNR with respect to a frontal target signal and is consequently used to form the output signal 68, which is converted into an output sound signal 72 in an output converter 70 of one of the two local devices 6, 8. The second directional signal 66 can either be used directly as the output signal 68 or can be subjected to a frequency-band-dependent amplification, in particular to compensate for a hearing impairment of the wearer 1, and possibly to dynamic compression.

[0046] The estimated target signal 42 can also be subjected to a particularly single-channel noise suppression 74 before the formation of the second directional signal 66. Furthermore, a different volume of the target signal component in the estimated target signal 42 and in the noise-suppressed first directional signal 64, which can result in particular from the different distances of the respective input transducers 30, 52, and 34 from the target signal source, but also from different sensitivities of the input transducers 30, 52, and 34 used, can be compensated for via a corresponding volume adjustment 76 depending on the probability 58 for a frontal target signal source.

[0047] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited to this embodiment. Other variations may be devised by those skilled in the art without departing from the scope of the invention. List of reference symbols 1 carrier 2 hearing aids 4 frontal conversation partners 6, 8 local device 10 Head of the wearer 12 target signal 14 directional noise 16 posterior hemisphere 18 speakers 20 mobile phone 22 Body of the wearer 30 first input converter 32 first input signal 34 external input converter 36 external input signal 40 adaptive filters 42 estimated target signal 44 estimated noise signal 46 first intermediate signal 48 Preprocessing 50 control signal 52 second input converter 54 second input signal 56 first directional signal 58 Probability for frontal target signal source 60 spectral noise power density 62 weight coefficients 64 noise-suppressed first directional signal 66 second directional signal 68 Output signal 70 output converters 72 Output sound signal 74 single-channel noise reduction 76 Volume adjustment

Claims

[1] Method for operating a hearing aid (2), - wherein a first input signal (32) is generated from a sound signal of the environment by a first input transducer (30) of the hearing aid (2), - wherein an external input signal (36) is generated from the ambient sound signal by an external input transducer (34) outside the hearing aid (2), - wherein, based on the first input signal (32) and the external input signal (36), a relative transfer function of the external input transducer (34) to the hearing aid (2) with respect to a target signal source (4) is determined, and the external input signal (36) is filtered with the relative transfer function, thereby generating an estimated target signal (42), wherein an estimated noise signal (44) is generated based on the estimated target signal (42) and the first input signal (32), wherein noise suppression in the hearing aid (2) is carried out on the basis of the estimated noise signal (44), wherein the estimated noise signal (44) is generated by subtracting the estimated target signal (42) from a first intermediate signal (46, 56) derived from the first input signal (32), wherein a first noise-suppressed signal is derived from the first input signal (32) as an intermediate signal (46, 56), wherein the estimated noise signal (44) is generated by subtracting the estimated target signal (42) from the first noise-suppressed signal, wherein the relative transfer function is determined by means of an adaptive filter (40) based on the external input signal (36), and where the estimated noise signal (44) is fed into the adaptive filter as the error signal. [2] Method according to claim 1, wherein a step size of the adaptive filter (40) is controlled in dependence on the first input signal (32) and / or the external input signal (36). [3] Method according to claim 1 or claim 2, - wherein a second input signal (54) is generated from the sound signal of the environment by a second input transducer (52) of the hearing aid (2), - wherein the relative transfer function of the external input transducer (34) to the hearing aid (2) with respect to the target signal source (4) is determined on the basis of the first input signal (32) and / or on the basis of the second input signal (54) and / or on the basis of the external input signal (36). [4] Method according to claim 3, wherein a first directional signal (56) is generated based on the first input signal (32) and the second input signal (54), and wherein the relative transfer function of the external input transducer (34) to the hearing aid (2) with respect to the target signal source (4) is determined on the basis of the first directional signal (56) and the external input signal (36). [5] The method of claim 4, wherein the estimated noise signal (44) is generated by subtracting the estimated target signal (42) from the first directional signal (56). [6] Method according to claim 5, wherein the relative transfer function is determined by means of an adaptive filter (40) based on the external input signal (36), wherein the estimated noise signal (44) is fed into the adaptive filter (40) as the error signal. [7] Method according to claim 6, wherein a probability (58) of a frontal target signal source (4) is determined on the basis of the external input signal (36) and the first input signal (32) and / or the second input signal (54), and wherein the step size of the adaptive filter (40) is controlled as a function of the probability (58) of a frontal target signal source (4). [8] Method according to one of claims 3 to 7, wherein the first input signal (32) and the second input signal (54) are each generated in two different local devices (6, 8) of a binaural hearing aid. [9] Method according to one of the preceding claims, wherein a noise suppression parameter (62) is determined on the basis of the estimated noise signal (44), which is applied to a second intermediate signal (56) derived from the first input signal (32), wherein an output signal (68) is generated from the noise-suppressed second intermediate signal (64), and wherein an output sound signal (72) is generated from the output signal (68) by an output transducer (70) of the hearing aid (2). [10] Method according to one of the preceding claims, wherein a second directional signal (66) is generated based on the estimated target signal (42) and the first input signal (32), wherein one or the output signal (68) is generated based on the second directional signal (66), and wherein one or the output sound signal (72) is generated from the output signal (68) by one or the output transducer (70) of the hearing aid (2). [11] Method according to claim 10 in conjunction with claim 4, wherein the second directional signal (66) is formed from the first directional signal (56) and the estimated target signal (42). [12] Hearing aid system, comprising - a hearing aid (2) with at least one first input transducer (30) for generating a first input signal (32), - an external input converter (34) for generating an external input signal (36) and - a processor unit which is configured to carry out the method according to one of the preceding claims. [13] Hearing aid system according to claim 12, wherein the hearing aid (2) further comprises a second input transducer (52) for generating a second input signal (54). [14] Hearing aid system according to claim 12 or 13, wherein the external input transducer (34) and the processor unit are arranged in a common housing (20).

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