Method for operating a hearing aid

Abstract

The invention relates to a method (24) for operating a hearing aid (2) in which an input signal (16) is generated by means of a microphone (6) based on ambient sound (7). Based on the input signal (16), an output signal (18) is provided, and an output sound (22) is emitted by means of a receiver (10) based on the output signal (18). The unprocessed ambient sound (22) present in the vicinity of the receiver (10) is determined, and the ratio (36) between the unprocessed ambient sound (22) and the output sound (12) is determined for different frequency bands. The amplitude of the output signal (18) for the frequency band is varied, whereby the ratio (36) lies between an upper limit (38) and a lower limit (40). The invention further relates to a hearing aid (2).

Description

[0001] The invention relates to a method for operating a hearing aid and to a hearing aid itself. The microphone comprises a microphone and a receiver.

[0002] People with hearing loss typically use a hearing aid. This usually involves an electromechanical transducer that captures ambient sound. The resulting electrical (audio) signals are amplified by an amplifier circuit and then output via another electromechanical transducer in the form of a receiver, thus delivering the sound into the person's ear canal. The captured audio signals are usually also processed, typically by a signal processor within the amplifier circuit. The amplification is adjusted to the specific hearing loss of the hearing aid user, who is also referred to as the user or wearer.

[0003] In this situation, it is possible that unprocessed ambient sound enters the person's ear canal in addition to the output sound. Depending on the hearing aid's design, this unprocessed ambient sound enters, for example, between the hearing aid and the edge of the ear canal, or between the receiver inserted into the ear canal and the edge of the ear canal, allowing the person to perceive it as well. This results in a superposition of the unprocessed ambient sound with the output sound. Since the output sound corresponds to the processed ambient sound, with frequency-specific amplification depending on the degree of hearing loss, nonlinear effects occur during this superposition—that is, artifacts that the person may perceive as disturbing.

[0004] One such artifact is the so-called comb filter. In this artifact, minima in the amplitude appear at specific frequency intervals in the frequency spectrum of the superimposed, unprocessed ambient sound and the output sound, with these minima being relatively sharply defined. The person perceives this superposition as if they were in a tunnel. The audibility of the comb filter artifact depends strongly on the type and level of the input signal. Due to the non-linear amplification of hearing aids and user-specific adjustments, the comb filter artifact varies between individuals. Therefore, implementing solutions for this is difficult.

[0005] One solution involves consistently attenuating frequencies that are more likely to cause the comb filter artifact. This makes these frequencies inaudible or barely perceptible to the user, even if, for example, no comb filter artifact is expected due to the current situation. Consequently, certain other algorithms, such as noise reduction, are also unavailable. Therefore, the benefit of the hearing aid for the user is reduced.

[0006] Another method involves attenuating / not amplifying the relevant frequencies during operation only when the current situation suggests a high probability of comb filter artifacts occurring. This relies on estimating the superposition, which is comparatively computationally intensive and prone to errors. If the estimation is incorrect, other artifacts can occur, and intelligibility for the user may also be reduced.

[0007] The invention is based on the objective of providing a particularly suitable method for operating a hearing aid and a particularly suitable hearing aid, wherein in particular comfort for a user is increased, and wherein hardware resources are expediently reduced.

[0008] With regard to the method, this problem is solved according to the invention by the features of claim 1, and with regard to the hearing aid by the features of claim 11. Advantageous further developments and embodiments are the subject of the respective dependent claims.

[0009] The process is used to operate a hearing aid. For example, the hearing aid is a headphone or includes a headphone, and the hearing aid is, for example, a headset. However, the hearing aid is most commonly referred to as a hearing aid device. The hearing aid device serves to support a person suffering from a reduction in hearing ability. In other words, the hearing aid device is a medical device by means of which, for example, partial hearing loss is compensated. The hearing aid device is, for example, a receiver-in-the-canal (RIC) hearing aid, an in-the-ear hearing aid such as an in-the-ear (ITC) or complete-in-the-canal (CIC) hearing aid, hearing glasses, or a pocket hearing aid. Alternatively, the hearing aid is a behind-the-ear (BTE) hearing aid, which is worn behind the ear.

[0010] The hearing aid is designed and configured to be worn on the human body. In other words, the hearing aid preferably includes a retention device that allows it to be attached to the human body. If the hearing aid is a hearing assistance device, it is designed and configured to be placed, for example, behind the ear or within an ear canal. In particular, the hearing aid is wireless and designed and configured to be inserted, at least partially, into an ear canal.

[0011] The hearing aid includes a microphone for capturing sound. Specifically, when in operation, the microphone captures ambient sound, i.e., sound waves, or at least a portion thereof. The microphone is advantageously located, at least partially, within the hearing aid's housing and is thus at least partially protected. The microphone is suitably an electromechanical transducer. For example, the microphone may have a single microphone unit or several microphone units that interact with each other. Each microphone unit advantageously has a diaphragm that is set into vibration by sound waves, and these vibrations are converted into an electrical signal by a suitable recording device, such as a magnet moving within a coil.Alternatively, the microphone units are designed capacitively, utilizing the fact that an applied electrical voltage changes when the distance between the diaphragm and a static surface of the microphone unit changes. In this case, the electrical voltage is applied specifically between the diaphragm and the static surface. The microphone units are preferably omnidirectional. In this or another way, it is at least possible to generate or at least provide an electrical signal using the microphone, based on the sound incident on the microphone, namely, in particular, ambient sound. This electrical signal constitutes an input signal.

[0012] Furthermore, the hearing aid has a receiver for outputting a signal. The output signal is, in particular, an electrical signal, and may be, for example, digital or, more appropriately, analog. The receiver is preferably an electromechanical transducer, such as a loudspeaker. Depending on the design of the hearing aid, in its intended state, the receiver is at least partially located within the ear canal of a user of the hearing aid, i.e., a person also referred to as the wearer, user, or hearing aid wearer, or at least acoustically connected to it. The hearing aid primarily serves to output the signal via the receiver, thereby generating a corresponding sound. In other words, the main function of the hearing aid is preferably to output the signal, thus generating the sound.

[0013] The hearing aid suitably includes a signal processing unit by means of which the microphone and the receiver are connected. Advantageously, the hearing aid has a signal processor that, for example, forms the signal processing unit or is at least a component thereof. The signal processor is, for example, a digital signal processor (DSP) or implemented using analog components. The signal processor, or at least the signal processing unit, is used in particular to adapt the input signal generated by the microphone, preferably to create the output signal. At a minimum, the signal processing unit is suitable for this purpose, and in particular is designed and configured accordingly. Advantageously, an analog-to-digital converter (ADC) is arranged between the microphone and the signal processing unit, for example, the signal processor, provided the signal processor is designed as a digital signal processor.Preferably, the hearing aid also includes an amplifier, or the amplifier is at least partially formed by the signal processing unit. For example, the amplifier is connected upstream or downstream of the signal processor in terms of signal processing.

[0014] The method involves generating the input signal from the ambient sound. In other words, the ambient sound is captured, and the input signal is created from it. The input signal is preferably an electrical signal, and its generation is expediently carried out using the microphone(s). The input signal corresponds, for example, to the unprocessed ambient sound or may already be processed. The input signal expediently has a specific directional characteristic, so that a particular part of the environment is amplified, specifically sound from a certain solid angle.

[0015] An output signal is generated from the input signal. For example, the input signal is directly mapped to the output signal. Preferably, however, the input signal is at least partially processed, and the processed input signal corresponds, in particular, to the output signal. The processing is carried out, for example, in one or more steps. In particular, frequency-specific amplification and / or mapping of certain frequencies to other frequencies occurs, resulting in compression. Alternatively or in combination with this, at least partial propagation delay is applied. Preferably, the signal processing unit is used for generating the output signal, and preferably for processing it.

[0016] During processing, it is advantageous to use frequency bands, whereby all frequencies within the same frequency band are processed identically. Alternatively, for example, only a single frequency from the respective frequency band is used and added to the output signal. The other frequencies are not processed further. This reduces the processing effort. Advantageously, the frequency bands are structured in such a way that the resulting discretization is imperceptible to the user.

[0017] The output sound is then emitted via the receiver based on the output signal. Specifically, the (electrical) output signal is converted into sound waves, for which the receiver is designed. At a minimum, the output sound is based on the output signal, and the output sound is emitted via the receiver when it receives the output signal. Thus, the output signal, namely the output sound, is perceptible to the user. Specifically, when the hearing aid is used as intended, the output sound is directed into the user's ear canal.

[0018] The method also determines the unprocessed ambient sound present in the area of ​​the receiver. When the hearing aid is used as intended, this area is advantageously located in the ear canal and preferably includes the eardrum. For example, the unprocessed ambient sound is measured directly, for instance, using an additional microphone positioned in the area of ​​the receiver. Alternatively, the unprocessed ambient sound is estimated, for which a transfer function is used. The input signal is fed to the transfer function. The transfer function may be determined theoretically and / or arise solely from the design of the hearing aid. In this case, the transfer function is the same for all users.Alternatively, this can be created specifically for each user, for example when adapting the hearing aid to the individual user.

[0019] For different frequency bands, the ratio between the unprocessed ambient sound and the output sound is determined. For example, each frequency band may contain only a single frequency, or preferably, each frequency band may be assigned adjacent frequencies. Preferably, the same frequency bands are used that were also used to generate the output signal.

[0020] In determining the ratio, the respective amplitude is taken into account in particular, and consequently, the ratio of the unprocessed ambient sound that penetrates the ear canal past the hearing aid to the possible processing by the signal processing unit, i.e., the output sound, is determined.

[0021] For this purpose, the output sound is measured directly, for example. However, it is particularly preferred that this sound is also determined theoretically, for which an additional transfer function is expediently used. This transfer function differs from the transfer function used to determine the unprocessed ambient sound. The additional transfer function depends on any processing of the input signal. In particular, the additional transfer function takes into account any frequency-selective amplification and / or a time offset, i.e., in particular, different propagation delays.

[0022] If the ratio is between an upper limit and a lower limit, the amplitude of the output signal is changed for this frequency band. This then changes the resulting ratio.

[0023] Consequently, a change in amplitude occurs when the ratio is at least approximately equal to 1, and when the amplitudes of the unprocessed ambient sound and the output sound are essentially the same. In this case, the potential artifacts resulting from superposition are comparatively pronounced, at least compared to a reduction at either amplitude. Due to the change in the output sound's amplitude, the strength of any potential artifact is reduced, so that if present, the artifact is either imperceptible or only faintly noticeable to a person. This increases user comfort.

[0024] Even in situations where, for example, no artifacts occur, the input signal can be processed in a way that is always adapted to the user's potential hearing loss, further increasing comfort. Furthermore, the process does not require any comparatively complex calculations, thus reducing the hardware resources needed.

[0025] For example, the processed ambient sound and the output sound are each measured to determine the ratio. However, it is particularly preferable to determine one or, more expediently, both of them—the unprocessed ambient sound and the output sound—using their respective transfer functions. This allows the ratio to be established before the output sound is actually emitted. Thus, it is possible to determine the ratio before the output sound is emitted, which is expediently done. If the ratio then lies between the upper and lower limits, the amplitudes of the output signal are appropriately modified, and only then is the output sound emitted based on this modified output signal. This completely avoids the formation of artifacts, further increasing comfort.

[0026] For example, this is performed for a single frequency band. Alternatively, it is performed for multiple frequency bands. Advantageously, the amplitude adjustment is modified for all or at least many frequency bands where the respective ratio between the upper and lower limits lies. This reduces potential interference across all or many frequency bands, further improving intelligibility. For example, different upper and lower limits are assigned to different frequency bands. Preferably, however, these limits are the same for all frequency bands, thus reducing the complexity.

[0027] The change in amplitude is, for example, always the same, or preferably dependent on the ratio, i.e., the value of the ratio. Alternatively, or in combination with this, the change in amplitude depends on other conditions, so that the current situation and / or different artifacts are taken into account. This further increases user comfort.

[0028] For example, to change the amplitude, it is set to a predefined value. For instance, the amplitude is increased. However, decreasing it is particularly preferred. Thus, this frequency range of the output signal is only perceived as reduced by the user via the corresponding output sound. Since the unprocessed ambient sound has an amplitude of the same order of magnitude in this frequency band, the corresponding frequency band remains perceptible. Therefore, the user is essentially unaware that the amplitude of the output signal has been reduced, and intelligibility remains high. This increases comfort.

[0029] For example, an upper limit of 20 dB or 10 dB is used. A particularly preferred upper limit is 6 dB. Alternatively, or in combination with this, a lower limit of -20 dB or -10 dB is used. Advantageously, a lower limit of -6 dB is used. In particular, an upper limit of 6 dB and a lower limit of -6 dB are used. Thus, amplitude adjustment occurs only when the amplitude of the unprocessed ambient sound and the output sound are essentially the same, i.e., when the probability of artifacts occurring is high.

[0030] Advantageously, the method only determines the amplitude for frequency bands with frequencies between 50 Hz and 5 kHz, between 100 Hz and 3 kHz, or between 200 Hz and 2.5 kHz, and modifies the amplitude if necessary. Advantageously, only the amplitude is modified for frequency bands with frequencies between 250 Hz and 2 kHz. In particular, the ratio is only determined for such frequency bands, and thus the respective transfer function is only used for the unprocessed ambient sound and / or the output sound. This reduces the effort. Furthermore, a comb filter artifact occurs predominantly at frequencies between 250 Hz and 2 kHz, or is at least bothersome to the user there. Therefore, the adjustment is only performed in the frequency range relevant to the user, whereas the unaltered output signal is used elsewhere.This reduces effort without compromising convenience. Furthermore, desired effects, which are incorporated through the appropriate generation of the output signal, are not unintentionally reversed.

[0031] Preferably, the gain factor assigned to the frequency band used to generate the output signal is changed to alter its amplitude. Specifically, the input signal is divided into different frequency bands to generate the output signal, with each frequency band being amplified by its own assigned gain factor. By changing the assigned gain factor, the resulting ratio is altered in the very step of generating the output signal, thus reducing the number of required steps and minimizing complexity.

[0032] For example, the amplification factor is increased. However, it is advantageously reduced so that this part of the output signal is essentially imperceptible. This prevents the output sound from being too loud, which could otherwise lead to a reduction in comfort.

[0033] For example, the gain factor is only changed in the frequency band where the ratio between the upper and lower limits lies. However, it is particularly preferred that the adjacent frequencies are also adjusted, preferably using a corresponding target function for this adjustment. This function is particularly notch-shaped. This ensures a smooth transition during the change, thus increasing ease of use. For example, to change the gain factor, it is multiplied by a predetermined number. However, it is particularly preferred that a specific constant is added or subtracted. Preferably, this constant is between 1 dB and 18 dB, suitably between 5 dB and 15 dB, and, for example, essentially equal to 10 dB.Thus, due to the change in amplitude, the ratio is also adjusted in such a way that no further adjustment is necessary, since the ratio is outside the upper and lower limits.

[0034] For example, the gain factor is changed relatively abruptly when the ratio between the upper and lower limits is... However, it is particularly preferable to adjust the gain factor gradually to the target value. This is specified, in particular, by means of a lookup table or a function. Once the target value is reached, no further adjustment is expediently made. In particular, the target value is between 5 dB and 15 dB, and preferably equal to 10 dB. Due to the gradual adjustment, an abrupt change, which would be unpleasantly perceptible to the user, is avoided. Consequently, comfort is increased.

[0035] For example, the amplitude is always changed when the ratio between the upper and lower limits is exceeded. Preferably, however, this only occurs when a criterion is met, i.e., an additional condition. This ensures that, for example, in situations where a ratio between the upper and lower limits is desired, the amplitude remains unchanged, which would otherwise negate a desired effect. Thus, it is possible to ensure that the adjustment only occurs when unwanted artifacts are present or at least possible, thereby increasing user comfort.

[0036] The criterion may, for example, comprise one or more conditions, and if at least one is met, the criterion is fulfilled. Alternatively, it may be necessary for certain conditions or a specific number of conditions to be met for the criterion to be fulfilled. Alternatively, it may be necessary for all conditions to be met.

[0037] For example, the amplitude is changed solely based on whether the criterion is met. However, the criterion is also particularly useful for determining the extent of the amplitude change. This allows for the targeted removal of unwanted artifacts.

[0038] The criterion is expediently met only if the amplitude is smaller than a reference amplitude by more than a third threshold, i.e., if a notch is present in the frequency spectrum. The reference amplitude is, in particular, the average of all amplitudes in the frequency range or at least in the adjacent frequency bands. Alternatively, the criterion is met only if the amplitude is larger than the respective reference amplitude by more than a fourth threshold, i.e., if a peak is present. The third and fourth thresholds are preferably of the same magnitude and, in particular, greater than 10 dB or at least greater than 5 dB. In this case, a change in amplitude essentially only occurs if a kind of comb-like structure is present, i.e., in particular, a relatively sharp minimum or maximum.For example, it is sufficient if the amplitude is only once smaller / larger than the reference amplitude by more than the respective limit value.

[0039] For example, the criterion is only met if, for a first set of frequency bands, the respective amplitude is smaller than the reference amplitude by more than the third limit. Alternatively, or particularly preferably in combination with this, the criterion is only met if, for a second set of frequency bands, the respective amplitude is larger than the respective reference amplitude by more than the fourth limit. The reference amplitude is specifically assigned to the respective frequency band and differs between the individual frequency bands. Consequently, each frequency band is not considered separately, but rather as a group. Preferably, the first set of frequency bands is greater than 1, and the second set is expediently greater than 2.Consequently, the adjustment only occurs if at least a slight comb-like structure is present in the frequency spectrum, comprising at least 3 peaks and 2 notches. This ensures that the desired effect or similar is not hindered by the adjustment, thus improving comfort.

[0040] Alternatively, or preferably in combination with other methods, the criterion is only met if the ambient noise is assigned to a specific class. In other words, the ambient noise is first examined and classified. A comparatively large number of stationary noises is considered a key criterion for classification. This is particularly the case when there are a relatively large number of speakers, engine noise predominates, especially traffic noise, or when machinery is in motion.

[0041] Alternatively, or preferably in combination, the criterion is only met if the strength of the comb filter artifact exceeds a certain threshold, such as 0.5, or if the comb filter artifact occurs as a result of the corresponding processing.

[0042] Preferably, the criterion is not met, particularly regardless of whether any other conditions are met, if the frequency band in which the ratio between the upper and lower limits lies corresponds solely to speech, specifically the user's speech or the speech of other people. In other words, the amplitude in this frequency band is caused solely by speech, and no other sound sources for these frequencies are present. Alternatively, or in combination with this, the criterion is not met if the frequency band corresponds solely to tonal music. In this case, the corresponding amplitude is present due to music that the user wishes to perceive, so that a change in the amplitude would lead to a distorted musical experience.In this case, the presence of a comb filter artifact is also rather unlikely, or at least it is not perceived as disturbing.

[0043] A hearing aid can be, for example, a headset or, more commonly, a hearing aid device. Examples include receiver-in-the-canal (RIC) hearing aids, in-the-ear (ITC) hearing aids, complete-in-canal (CIC) hearing aids, hearing glasses, or pocket hearing aids. Alternatively, a hearing aid can be a behind-the-ear (BTE) hearing aid, which is worn behind the ear.

[0044] The hearing aid includes a microphone. This microphone is, for example, omnidirectional, or its directional characteristics can be adjusted. For this purpose, the microphone preferably has two or more microphone units. The microphone is designed and configured to capture ambient sound. Advantageously, an input signal is generated by the microphone when ambient sound is detected. The hearing aid advantageously includes a signal processing unit, which is preferably connected to the microphone. In particular, the input signal is fed to the signal processing unit during operation. The hearing aid includes a receiver, which outputs a signal that advantageously corresponds to the processed audio signal and is advantageously connected to the signal processing unit.

[0045] The hearing aid operates according to a method in which the microphone generates an input signal based on ambient sound. An output signal is provided based on this input signal, and an output sound is emitted via the receiver based on this output signal. The unprocessed ambient sound present in the receiver's vicinity is determined, and the ratio between the unprocessed ambient sound and the output sound is calculated for different frequency bands. The amplitude of the output signal for the frequency band is then adjusted to match the ratio between an upper and a lower limit. Advantageously, the signal processing unit is suitable, and in particular designed and configured, to perform at least one or both of these methods.

[0046] The invention further relates to a hearing aid system with two such hearing aids, i.e., a binaural hearing aid system. For example, the method is carried out separately using each hearing aid. Preferably, however, a signal exchange takes place between them, and if the amplitude is changed in one of the hearing aids, the amplitude is also changed in the other hearing aid at the same frequency band, expediently regardless of the ratio between the two. Thus, even with a binaural hearing aid system, coordinated behavior is maintained, which does not lead to a deterioration of the acoustic experience for the user.

[0047] The further training and advantages explained in connection with the procedure can also be applied analogously to the hearing aid / hearing aid system and to each other, and vice versa.

[0048] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows: Fig. 1 schematically simplified a hearing aid, Fig. 2 a method for operating the hearing aid, Fig. 3 a frequency spectrum in which a comb filter artifact is present, and Fig. 4 a function for changing a gain factor.

[0049] Corresponding parts are marked with the same reference symbols in all figures.

[0050] In Figure 1A simplified schematic representation of a hearing aid 2 is shown. The hearing aid 2 has a housing 4, inside which a microphone 6 is arranged. Ambient sound 7 can be detected by means of the microphone 6. The microphone 6 has several microphone units (not shown in detail), each designed as an electromechanical transducer or a capacitive transducer. A signal processing unit 8 is connected downstream of the microphone 6. A receiver 10 is connected downstream of the signal processing unit 8, by means of which, when used as intended by a user, it is possible to output sound 12 into the ear canal of the user (not shown in detail).

[0051] The signal processing unit 8 includes a processing unit 14, which processes an input signal 16 provided by the microphone 6 during operation, resulting in an output signal 18. This process begins with splitting the signal into different frequency bands, with each band being processed separately. This allows for frequency-selective amplification and / or attenuation, suppressing noise or other unwanted sounds. The processing unit 14 includes, for example, a digital sound processor. Compression is also performed, reducing the frequency spectrum of the output signal 18 compared to the input signal 16.

[0052] The output signal 18 is routed to the receiver 10, so that the output sound 12 emitted by means of the receiver 10 corresponds to the output signal 18.

[0053] The signal processing unit 8 also includes an estimation unit 20, which also receives the input signal 16. The estimation unit 20 comprises two transfer functions. One of these determines the resulting output sound 12 based on the input signal 16. This is done theoretically, for which the operations to be performed by the processing unit 14 are simulated and a frequency response of the receiver 10 is taken into account. The other transfer function estimates the portion of the ambient sound 7 entering the ear canal past the hearing aid 2, so that the unprocessed ambient sound 23 present in the area of ​​the receiver is determined. The geometric design of the housing 4, such as holes, and / or the ear canal is taken into account. This transfer function is created based on a measurement and is adapted to the respective user.If the processing unit 14 and / or the receiver 10 are not operated, i.e., if the output sound 12 is not generated, the user thus only perceives the unprocessed ambient sound 22, which is dampened, for example, due to the presence of the hearing aid 2 compared to the ambient sound 7.

[0054] In Figure 2 A procedure 24 for operating the hearing aid 2 is shown. In a first step 26, the input signal 16 is generated using the microphone 6 based on the ambient sound 7. This signal is then sent to the signal processing unit 8, namely to the processing unit 14 and the estimation unit 20.

[0055] In a subsequent second step 28, the output sound 12 and the unprocessed ambient sound 22 are determined using the estimation unit 20 based on the transfer functions. It is possible that, due to the superposition of the output sound 12 with the unprocessed ambient sound 22 in the ear canal, particularly in the area of ​​the eardrum, a frequency spectrum 30 shown in Figure 3 results. In the frequency spectrum 30 shown, a comb filter artifact 32 occurs due to unfavorable interference between the output sound 12 and the unprocessed ambient sound 22. This artifact exhibits several relatively sharp minima, which have a pre-existing frequency separation from each other. These separations depend on the frequency-specific amplification and the anatomy of the ear canal and therefore differ between users.

[0056] In a subsequent third step 34, a ratio 36 between the unprocessed ambient sound 22 and the output sound 12 is determined for the different frequency bands into which the input signal 16 is divided. Here, the respective ratio 36 is determined only for all frequency bands with frequencies between 250 Hz and 2 kHz.

[0057] If the ratio 36 is greater than an upper limit 38 or less than a lower limit 40, a fourth processing step 42 is performed. The upper limit 38 is set at 6 dB and the lower limit 40 at -6 dB. In the fourth processing step 42, the input signal 16 is processed by the processing unit 14 according to the user's potential hearing loss, and the output signal 18 is generated based on the input signal 16. The output signal 18 is then routed to the receiver 10, so that the output sound 12 is emitted by the receiver 10 based on the output signal 18.

[0058] However, if the ratio 36 lies between the upper limit 38 and the lower limit 40, a fifth step 44 is performed. In this step, it is checked whether a criterion 46, which comprises several conditions, is fulfilled. For example, fulfilling one condition is sufficient for criterion 46 to be fulfilled. Alternatively, fulfilling further conditions is required for criterion 46 to be fulfilled.

[0059] To verify compliance with one of the conditions, the ambient noise is classified as 7. This involves checking for the presence of stationary noise caused by speech from many speakers. It also checks whether the stationary noise is caused by engine noise, such as car noise or the operation of heavy machinery. If this is the case, then criterion 46 is met. Consequently, criterion 46 is only met if the ambient noise is assigned to a specific class.

[0060] Another such condition is that the amplitude of the respective frequency band is smaller by more than a third limit value, or larger by a fourth limit value, than a reference amplitude. The reference amplitude is the average of the amplitudes of the directly adjacent frequency bands of the output sound 12. The third limit value, like the fourth limit value, is equal to 10 dB. If this is the case, then criterion 46 is also fulfilled.

[0061] As a further condition, it is checked whether, for several of the frequency bands (specifically, for a first number of 2), the respective amplitude is smaller than the respective reference amplitude by more than the third limit. It is also checked whether, for several of the frequency bands (specifically, for a second number of 3), the respective amplitude is larger than the respective reference amplitude by more than the fourth limit. If this condition is met, the comb filter artifact 32 is present.

[0062] Regardless of whether any of the other conditions are met, criterion 46 is always not met if the frequency band corresponds solely to speech or tonal music. That is, if only speech or tonal music contributes to the respective amplitude in the respective frequency band. The speech can be produced by a single other speaker or by the user of hearing aid 2 themselves.

[0063] If criterion 46 is not met, for example, because none, not all, or at least not a predetermined number of conditions are fulfilled, or if the frequency band corresponds solely to speech or tonal music, the fourth processing step 42 is also carried out. Otherwise, a sixth processing step 58 is carried out. In this step, a gain factor 50 assigned to the frequency band is changed, namely reduced. This is done for all frequency bands where the ratio 36 between the two limit values ​​38 and 40 is correct, and where criterion 46 is met. The changed gain factors 50 are then passed to processing unit 14.

[0064] The fourth step, 42, is then carried out again. However, the amplification factors 50, modified in the sixth step 48, are used for the respective frequency bands. For the remaining frequency bands, the amplification factors specified based on the hearing loss are used.

[0065] Due to the changed gain factors 50, the amplitude of the output signal 18 is altered. Consequently, the resulting ratio of the frequency bands between the unprocessed ambient sound 22 and the output sound 12 is either above the upper limit 38 or below the lower limit 40, thus avoiding the formation of the comb filter artifact 32. Since the ratio 36 is only created for frequency bands between 250 Hz and 200 kHz, only the amplitude for the frequency bands with frequencies between 250 Hz and 2 kHz is changed. Furthermore, the amplitude of the frequency bands is only changed if criterion 46 is met.

[0066] The changes to the amplification factor 50 in the sixth work step 48 depend on the ratio 36. In Figure 4The graph shows a function of the changes in the gain factor 50 against the ratio 36, with dB Id used as the unit on the axes. For a ratio between -0.5 dB Id (log dualis; log2) and 1 dB Id, 10 dB Id is subtracted from the gain factor to account for the change, resulting in a reduction of 60 dB. From a ratio of 36, from 1 dB Id up to 6 dB Id, the reduction decreases linearly. For example, at a ratio of 3 dB Id, 5 dB Id is subtracted from the gain factor 50. Consequently, the function is essentially notched.

[0067] The function specifies the target value for the change in the amplification factor of 50. The change itself occurs gradually, over a specific timeframe, towards the target value specified by the function. This avoids a harsh transition that would otherwise be perceived as unpleasant by the user.

[0068] The invention is not limited to the embodiment described above. Rather, other variants of the invention can also be derived by a person skilled in the art without departing from the subject matter of the invention. In particular, all individual features described in connection with the embodiment can also be combined with one another in other ways without departing from the subject matter of the invention. Reference symbol list

[0069] 2 Hearing aid 4 Housing 6 Microphone 7 Ambient sound 8 Signal processing unit 10 Receiver 12 Output sound 14 Processing unit 16 Input signal 18 Output signal 20 Estimation unit 22 Unprocessed ambient sound 24 Procedure 26 First step 28 Second step 30 Frequency spectrum 32 Comb filter artifact 34 Third step 36 Ratio 38 Upper limit 40 Lower limit 42 Fourth step 44 Fifth step 46 Criterion 48 Sixth step 50 Gain factor

Claims

1. Method (24) for operating a hearing aid (2) in which - an input signal (16) is generated by means of a microphone (6) based on an ambient sound (7), - an output signal (18) is provided based on the input signal (16), and - an output sound (22) is emitted by means of a receiver (10) based on the output signal (18), - wherein the unprocessed ambient sound (22) present in the area of ​​the receiver (10) is determined, - wherein the ratio (36) between the unprocessed ambient sound (22) and the output sound (12) is determined for different frequency bands, and - wherein an amplitude of the output signal (18) is changed for the frequency band in which the ratio (36) lies between an upper limit (38) and a lower limit (40).

2. Method (24) according to claim 1, characterized by that The upper limit (38) 6 dB and / or the lower limit (40) -6 dB may be used.

3. Method (24) according to claim 1 or 2, characterized by that The amplitude is only changed for frequency bands with frequencies between 250 Hz and 2 kHz.

4. Method (24) according to any one of claims 1 to 3, characterized by that a gain factor (50) assigned to the frequency band is changed, by means of which the output signal (18) is created.

5. Method (24) according to claim 4, characterized by that the amplification factor (50) is gradually adjusted to a target value.

6. Method (24) according to any one of claims 1 to 5, characterized by that the amplitude is only changed if a criterion (46) is met.

7. Method (24) according to claim 6, characterized by that The criterion is only met if the amplitude is smaller than a reference amplitude by more than a third limit value or larger than a fourth limit value.

8. Method (24) according to claim 7, characterized by that criterion (46) is only met if, for a first number of frequency bands, the respective amplitude is smaller than the respective reference amplitude by more than the third limit, and / or if, for a second number of frequency bands, the respective amplitude is larger than the respective reference amplitude by more than the fourth limit.

9. Method (24) according to any one of claims 6 to 8, characterized by that criterion (46) is only met if the ambient sound (7) is assigned to a specific class.

10. Method (24) according to any one of claims 6 to 9, characterized by that Criterion (46) is not met if the frequency band corresponds only to speech or tonal music.

11. Hearing aid (2) comprising a microphone (6) and a receiver (10) and operated according to a method (24) according to any one of claims 1 to 10.

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