EP1750481A2 - Automatic gain setting for a hearing aid - Google Patents

Abstract

The method involves defining maximum gain of audio signal at different frequencies, and determining target gain of the audio signal at different frequencies. The resulting gain of audio signal at one frequency is set to target gain if target gain does not exceed maximum gain, and is limited to maximum gain if target gain exceeds maximum gain. The resulting gain is increased above target gain and is limited to maximum gain, at another frequency, if resulting gain is limited to maximum gain at previous step. Independent claims are also included for the following: (1) adjustment device for hearing aid; and (2) hearing aid.

Description

The invention relates to a method for setting or operating a hearing aid and a hearing aid with at least one input transducer for receiving an input signal and conversion into an audio signal, a signal processing unit for processing and amplification of the audio signal and an output transducer.

In modern hearing aid devices, there are various possibilities for setting the transfer function, that is to say the amplification of an input signal over the frequency. In particular, the transfer function of a modern hearing aid can be adjusted in the adaptation of the hearing aid to the individual hearing loss of a user.

From the DE 44 18 203 C2 a method is known for adjusting the transmission characteristic of a hearing aid by means of a personal computer, a memory for base values of a hearing aid setting in conjunction with an algorithm and a data memory providing a transmission characteristic of the hearing aid and displaying it on the display of the personal computer as a graphical curve.

In addition, it is also known that the transmission behavior of a hearing aid device can also change during normal operation of the hearing aid. On the one hand, the user can change the transmission characteristics of the hearing aid by manual operation of controls that are attached to the hearing aid or a remote control. For example, it is possible to switch between different hearing programs or to vary the volume setting. In addition, modern hearing aids are often equipped with different automatic systems, depending on the current environmental situation or specific System states automatically influence the transfer function.

From the DE 101 31 964 A1 a method for operating a hearing aid is known in which a transfer characteristic of a maximum gain over the frequency is set. If, as a result of an automatic or manual change of parameters which relate to the signal processing in the hearing aid, the amplification be increased at least in a certain frequency range beyond the characteristic of the maximum amplification, the resulting gain in this frequency range is automatically adjusted to the preset maximum amplification for limited to the relevant frequency range.

Hearing aid carriers often have the problem that the speech intelligibility despite the use of a hearing aid does not match the speech intelligibility of a normal hearing. Different speech intelligibility models are known from the prior art which show which frequency ranges are particularly important for speech intelligibility. This knowledge can also be advantageously used for setting up speech reproducing or transmitting devices such as hearing aids.

From the US 5,729,658 For example, a method is known with which speech intelligibility can be quantified in a device that transmits, amplifies or reproduces acoustic speech signals. This makes it possible to compare different devices or different settings of a device with regard to their voice playback.

Hearing Aids continue to pose the problem of acoustic feedback (feedback). These are particularly common when it comes to hearing aids with high gain. The feedbacks are expressed in strong feedback oscillations of a certain frequency. This "whistling" is usually for both Hearing aid carrier as well as for people in its immediate vicinity very uncomfortable. The typical feedback for pipes is usually at relatively high frequencies. Feedback can occur when sound picked up from the hearing aid microphone, amplified by a signal amplifier and output through the handset, returns to the microphone and is amplified again. However, for typical whistling, usually at a dominant frequency, two additional conditions must be met. The so-called loop gain of the system, ie the product of the hearing aid gain and the attenuation of the feedback path, must be greater than one. In addition, the phase shift of this loop gain must correspond to any integer multiple of 360 °.

The simplest approach to reducing feedback-induced oscillations is to permanently reduce hearing aid gain so that the loop gain remains below the critical limit in adverse situations. The decisive disadvantage, however, is that this limitation can no longer achieve the hearing aid reinforcement required for severe deafness.

Through a so-called open-loop gain measurement, the course of the critical amplification can be determined. Here, the critical gain is the gain that must not be exceeded so that feedback does not occur in a hearing aid worn by an individual. However, this leads to the fact that, especially in the case of the higher frequencies transmitted by the hearing aid, the adjustable amplification can no longer completely compensate for the hearing loss of the hearing aid wearer. That is, instead of the target gain needed to compensate for the hearing damage, a lower resulting gain is set, which is limited to the critical gain. In general, the resulting gain is even set lower than the critical gain by a certain amount to give a "safety margin" from the critical gain to grant. In this case, the problem arises that, under the reduction in gain, as a rule, speech intelligibility is passed in a speech signal transmitted by the hearing aid.

An object of the invention is to automatically adjust parameter settings in a hearing aid device so that improved speech intelligibility results in a speech signal transmitted by the hearing aid.

This object is achieved by a method with the method steps according to claim 1.

In a hearing aid device, an input signal is generally received by means of an input transducer and converted into an electrical input signal. Usually serves as an input transducer at least one microphone which receives an acoustic input signal. Modern hearing aids often comprise a microphone system with a plurality of microphones in order to achieve a direction dependent on the direction of arrival of acoustic signals reception, a directional characteristic. However, an input transducer can also be designed as a telecoil or as an antenna for receiving electromagnetic input signals. The input signals converted by the input transducer into electrical input signals are fed to a signal processing unit for further processing and amplification. The further processing and amplification takes place to compensate for the individual hearing loss of a hearing aid wearer, as a rule, as a function of the signal frequency. The signal processing unit outputs an electrical output signal, which is fed via an output transducer to the hearing of the hearing aid wearer, so that the latter perceives the output signal as an acoustic signal. As output transducers usually listeners are used, which generate an acoustic output signal. However, output transducers for generating mechanical vibrations are also known, which directly excite certain parts of the ear, such as the ossicles, to vibrate. Farther output transducers are known which directly stimulate nerve cells of the ear.

The method according to the invention can be carried out both in the adaptation of a hearing aid to the individual hearing loss of a hearing aid wearer, in which the settings are performed on a programming device, but it can also be performed during ongoing operation of the hearing aid.

Frequently, in a hearing aid, the gain that would be required to compensate for the individual hearing loss of a hearing aid wearer can not be adjusted for the entire frequency spectrum that can be transmitted by the hearing aid. This is the case in particular for avoiding feedback. The gain of the hearing aid is therefore limited individually for each hearing aid wearer to a maximum gain. The exact course of the respective maximum amplification can be determined, for example, by means of an open-loop gain measurement. From such a measurement, a transmission characteristic determined for the hearing aid and the individual user results in a maximum amplification of an input signal over the frequency.

Furthermore, a target gain is determined, which would be required to compensate for the individual hearing loss of the hearing aid wearer. For the frequency ranges in which the target gain is above the critical gain, the resulting gain, ie the gain actually set in the hearing aid, must not exceed the critical gain. The actual gain setting is therefore limited to the critical gain in the frequency ranges where the target gain is above the critical gain. In general, one will even provide a "safety margin" of the resulting gain from the critical gain to feedbacks To be able to largely exclude even in everyday use of the hearing aid.

By reducing the resulting gain compared to the target gain, speech intelligibility for a hearing aid wearer supplied with the relevant hearing aid device is usually impaired. The essence of the invention is now to automatically compensate for speech intelligibility when, in a particular frequency range, a resulting gain must be set that is below the actual desired target gain.

The invention can be applied to all known types of hearing aid devices, for example hearing aid devices that can be worn behind the ear, hearing aid devices that can be worn in the ear, implantable hearing aid devices or pocket hearing aid devices. Furthermore, the hearing aid according to the invention may also be part of a plurality of devices for supplying a hearing aid comprising comprehensive hearing aid system, e.g. Part of a hearing aid system with two worn on the head hearing aids for binaural care or part of a hearing aid system, consisting of a portable on the head device and a wearable processor unit.

FIG 1

ein Ablaufdiagramm für ein Verfahren gemäß der Erfindung,

FIG 2

ein mit einem Anpassgerät verbundenes Hörhilfegerät,

FIG 3

eine Kennlinie einer Zielverstärkung über der Frequenz,

FIG 4

die Kennlinie der Zielverstärkung sowie eine Kennlinie einer maximalen Verstärkung über der Frequenz,

FIG 5

eine gemäß der Erfindung eingestellte resultierende Verstärkung,

FIG 6

ein Hörhilfegerät gemäß der Erfindung im Blockschaltbild.

The invention will be explained below with reference to exemplary embodiments. Show it:

FIG. 1

a flow chart for a method according to the invention,

FIG. 2

a hearing aid connected to an adapter,

FIG. 3

a characteristic of a target gain over the frequency,

FIG. 4

the characteristic of the target gain and a characteristic of a maximum gain over the frequency,

FIG. 5

a resulting gain set according to the invention,

FIG. 6

a hearing aid according to the invention in the block diagram.

FIG. 1 illustrates the essential method steps when carrying out a method according to the invention. First, for an individual hearing aid wearer to be provided with a particular hearing aid, a target gain and a maximum gain above the frequency are set. The target gain is the gain that you actually want to achieve with the hearing aid, for example, to compensate for the hearing loss of the hearing aid wearer. The maximum gain is the maximum gain that can be achieved with the hearing aid in question, taking into account the technical and anatomical conditions as a function of the frequency of an input signal. The order of the two process steps mentioned above is irrelevant.

In a subsequent method step, it is checked whether the target gain at a certain frequency or for a certain frequency range exceeds the maximum gain. If this is the case, then for these frequencies the resulting gain, that is to say to be set in the hearing aid, is limited to the maximum gain. In this case, if appropriate, a "safety margin" of the resulting gain from the maximum gain by which the resulting gain actually set in the hearing aid device remains below the maximum gain can be taken into account.

To compensate for this gain limit then automatically set in the hearing aid gain at another frequency or in another according to the invention Frequency range for which the target gain is below the maximum gain, compared to the target gain raised.

Figure 2 shows a schematic representation and with different scales designed as a personal computer (PC) 1 fitting device with a computer mouse 2 and a connectable via a not-shown interface via a cable 3 programmable hearing aid 4. A via a mouse button 5 operable pointer 6 is on Screen 7 of the PC indicated. In the data processing system 8 of the PC are provided in a conventional manner and also not shown data storage and computing devices.

The described method can proceed on the adapter 1 for adapting the hearing aid 4 to an individual hearing loss. For this purpose, the target gain, the maximum gain and the resulting gain can be represented, for example, as transfer characteristics on the graphical user interface. The limitation of the resulting gain on the maximum gain can be done manually, for example, by clicking and dragging the characteristic of the resulting gain with the mouse 2. However, the limitation of the resulting gain to the maximum gain can also be automatic. It is essential in the context of the invention that whenever a resulting gain below the target gain must be set at a particular frequency or in a particular frequency range, compensation is automatically provided by at least one other frequency or at least one other frequency range Raising the resulting gain compared to the target gain takes place, wherein the increase of course can only take place to the extent that while the maximum gain at this other frequency or this other frequency range is not exceeded.

It should be noted that the described method is in fact carried out even if the target gain and the resulting gain are not displayed simultaneously as two different transfer characteristics at the user interface. For example, only one hearing aid transmission characteristic curve could always be displayed, which is then set during the programming of the hearing aid device. This transfer characteristic is given once, for example using a first-fit algorithm, and then changed in the course of the adaptation. The transfer characteristic defined at the beginning of the adaptation would then correspond to the target gain and the transfer characteristic of the resulting gain obtained at the end of the adaptation, which is finally set on the hearing aid. Thus, although a target gain and a resulting gain on the user interface would be visible, but not simultaneously but temporally successive. However, to illustrate the invention, the distinction between target gain, maximum gain, and resultant gain is more appropriate.

However, as with the adaptation of a hearing aid device, the method according to the invention can also be carried out during the ongoing operation of a hearing aid. Namely, modern hearing aids offer a number of ways by which the transfer characteristic of the hearing aid is changeable during operation. In the simplest case, such a hearing aid includes, for example, a volume control with which the volume and thus the gain can be manually raised or lowered. In addition, several different methods are known in hearing aids that automatically change the transfer function of the hearing aid. For example, methods for automatically adapting the signal processing in a hearing aid to different environmental situations are mentioned. This may also result, during operation, in the desire to set a target gain that is at least one frequency for the individual hearing aid wearer and the hearing aid in question exceeds the maximum gain set. In order to avoid feedback, however, only a resulting gain is set, which is at most equal to the maximum gain, but this does not exceed. This too can lead to a deterioration in speech intelligibility in the supply of a user with the relevant hearing aid device due to the deviation of the resulting amplification from the actually desired target amplification. Again, the invention contemplates compensating for the deterioration in speech intelligibility resulting from the difference between the target gain and the resulting gain. This is achieved in the hearing aid according to the invention in that, for compensation, the gain in another frequency range in which the maximum gain is above the target gain is automatically set to a resultant gain between the target gain and the maximum gain. In other words, the gain reduction in a first frequency range required for technical reasons, in particular to avoid feedback, is at least partially compensated by an automatic gain boost in a second frequency range.

According to the invention, the increase of the resulting gain beyond the target gain is preferably done using a speech intelligibility model. It has been shown that certain frequency ranges have a much greater influence on speech intelligibility than other frequency ranges. In particular, the frequency range in the range of one kHz is particularly important for the understanding of speech. In contrast, feedback usually only occurs at higher frequencies. Thus, the setting of the gain below the actually desired target gain in terms of speech intelligibility can be mitigated by raising the frequencies in the range by a kHz. With the help of a speech intelligibility model In this case, it is even possible to optimize the speech intelligibility by determining, for example by means of the speech intelligibility model, an optimum with regard to the frequency range and the exact amount of the increase. Of course, the increase can only take place within a certain framework, which is limited for example by the maximum amplification, the individual discomfort threshold of the hearing aid wearer or the perceived loudness of a signal transmitted with the hearing aid. In particular, the gain adaptation advantageously takes place not only on the basis of a speech intelligibility model, but possibly also on the basis of a loudness model. Thus, it can be advantageously determined as a further framework condition in the automatic gain adjustment that overall the loudness impression does not change or changes only slightly.

In FIGS. 3 to 5, the procedure according to the invention is illustrated graphically on the basis of transfer characteristics. FIG. 3 shows the characteristic curve of a target gain V _z over the frequency for an individual person. This target gain results, for example, from an audiogram of the hearing aid wearer. In addition to the audiogram but can also enter a number of other parameters in the determination of the target gain, for example, individual user input to a programmer during the adaptation of the hearing aid in question. In addition, the target gain can also change during the ongoing operation of the hearing aid, either by manually made settings of the user (eg manual change in volume setting) or automatically, eg by running in the hearing aid algorithms, such as situation detection, automatic gain control (AGC) , for feedback suppression etc.

The characteristic V _z in the embodiment shows the required under the current circumstances to compensate for the individual hearing loss target gain of an input signal through the hearing aid. Due to technical and anatomical conditions, however, it is often not possible to actually set this target gain in the hearing aid in question. In the exemplary embodiment, only the maximum gain V _MAX additionally drawn in FIG. 4 relative to FIG. 3 can be set for the hearing aid device to be set and the relevant user. The characteristic curve V _MAX can for example result from an open-loop gain measurement and take into account the feedback tendency of the hearing aid device for the individual user. As can be seen from FIG. 4, the characteristic curve V _Z exceeds the characteristic curve V _{MAX to the} right of the common intersection S. This means that in order to avoid feedbacks in this frequency range, the target amplification V _{Z can not be set} for the relevant hearing aid device. Prior to the invention, therefore, a gain characteristic V _{E has been} set, which corresponds to the left of the intersection S substantially the target gain V _z and right of the intersection S with a certain safety margin below the maximum gain V _MAX . The difference between V _E and V _Z generally leads to a deterioration in speech intelligibility in a hearing aid wearer supplied with the relevant hearing aid device.

From Figure 5, the inventive automatic increase of the resulting gain V _RES over the target gain V _{Z is} clear. The increase is in particular also graphically highlighted by the arrows. It can be seen that in particular the frequency range above and below one kHz is raised compared to the originally intended target gain. The increase is preferably carried out on the basis of a speech intelligibility model, by which a value for the gain in speech intelligibility is generated for different frequencies and different amounts of the respective increase, so that an optimum for speech intelligibility can be achieved with the aid of known optimization methods. In addition, the increase in gain takes place additionally under Consideration of a loudness model, which provides a measure of the loudness impression of a signal amplified according to the characteristics shown. In this case too, the characteristic V _E according to FIG. 4 set in relation to the target characteristic V _Z produces a lowering of the volume, which can be at least partially compensated for by the increase in the gain at lower frequencies, as shown in FIG. Advantageously, the speech intelligibility is optimized taking into account the loudness such that an improvement in speech intelligibility is achieved without substantially increasing the loudness perceived by the user.

In carrying out the method according to the invention during operation of the hearing aid device in question, both the gain reduction and the gain increase are carried out automatically in order to get from the target gain V _Z to the resulting gain V _RES . For this purpose, appropriate algorithms for adjusting the gain are implemented in the hearing aid.

Even when carrying out the method according to the invention in an adapter, there is the possibility that after determining the maximum gain V _MAX and after determining the target gain V _Z, a resulting gain V _RES for the entire frequency range that can be transmitted with the hearing aid is generated automatically according to the invention , In addition, it is also possible that the user of the fitting device makes manual adjustment to the transfer characteristics by, for example, with a pointing device clicks on a curve and pulls, with in such a reduction in gain at a frequency or a frequency range then automatically according to the invention Otherwise, a change in the transfer characteristic V _RES takes place so that, overall, at most a slight deterioration in speech intelligibility results from the gain reduction.

FIG. 6 shows by way of example in block diagram form a hearing aid with a gain control according to the invention. As an input transducer in the hearing aid device 10 according to Figure 4 is a microphone 11 which receives an acoustic signal and in an audio signal, that is, an electrical sound signal, converts. The resulting audio signal is first supplied to a preamplifier and A / D converter unit 12, in which the initially analog audio signal is converted into a digital audio signal. For further processing in several parallel channels of the hearing aid, the digital audio signal is split by means of the filter bank 13 into a plurality of frequency bands (channels). The audio signals of the individual channels are first fed to signal processing units 14A-14E in which the audio signals, for example for adaptation to the individual deafness of a hearing aid wearer, are filtered differently. Further, in the signal processing units 14A-14E, signal analysis is also performed to detect, for example, the signal level, to detect the current listening situation, or to detect the presence of noise. From this signal analysis, parameters are derived and fed to automatic gain control units 15A-15E. The latter also includes parameters stored in a memory 16 which indicate a normal gain as well as a maximum amplification of the audio signal over the frequency for the respective channel. The normal gain sets a gain output value for each frequency of the transmittable frequency range in the gain calculation, and may be determined both by a default setting of gain by the hearing aid manufacturer and by a setting made by the acoustician when adjusting the hearing aid. Likewise, the maximum gain can be preset by the hearing aid manufacturer and adjusted individually by the acoustician. For both gains almost any waveforms of the gain over the frequency in the audible frequency range can be adjusted. As shown in the embodiment, the automatic gain control units 15A-15E may continue to receive the current one Adjustment of a volume control 17 be supplied. From parameters supplied to automatic gain control units 15A-15E, they determine a particular target gain for each frequency. For example, for a channel, the normal gain may be 50 dB (gain output value), because of a very high signal input level, a factor of 0.8 compression (1st gain change value) will increase the signal by 10 dB due to the volume control 17 (FIG. Gain alteration value) and finally lowered by 20 dB due to a detected spurious signal (3rd gain change value), so that taking into account all the gain change values, a total gain change value of -20 dB and thus a target gain of 30 dB result. If this target gain at the respective frequency is less than or equal to the maximum gain, then this gain is also the effective resulting gain. Otherwise, the target gain is limited to the maximum gain so that the latter forms the effective resulting gain. In the latter case, the invention then takes effect, so that the undesired but necessary reduction in gain is at least partially compensated by an increase in gain in another frequency range. For this purpose, a data exchange between the individual automatic gain control units 15A to 15E is provided, which cause the increase of the gain according to the invention in at least one frequency band. The increase advantageously takes place on the basis of a speech intelligibility model and a loudness model. In the embodiment, amplifiers 18A to 18E in the channels of the hearing aid 10 are respectively controlled by the automatic gain control units 15A to 15E. After the amplification, the audio signals of the individual channels are brought together again and, if appropriate, after signal processing in the signal postprocessing unit 19, in which, for example, filtering, final amplification and D / A conversion takes place, a receiver 20 is supplied. This converts the processed electrical audio signal back into an acoustic signal, which is delivered into the ear canal of the hearing aid wearer.

The invention offers the advantage that in the case of the relevant hearing aid device 10, the gain, taking account of anatomical and technical conditions, is regulated in such a way that optimal speech intelligibility and an optimal loudness impression are achieved.

Claims (11)

Method for setting or operating a hearing aid (4, 10) with at least one input transducer (11) for receiving an input signal and conversion into an audio signal, a signal processing unit (12-19) for processing and frequency-dependent amplification of the audio signal and an output transducer (20) for producing an output signal which can be recognized by a user as an acoustic signal, comprising the following steps: Setting a maximum gain (V _MAX ) of the audio signal for at least a first and a second frequency of the audio signal, Determining a target gain (V _Z ) for the first and the second frequency of the audio signal, Setting the resulting gain (V _RES ) at the first frequency of the audio signal, the resulting gain (V _RES ) coinciding with the target gain (V _Z ) when the target gain (V _Z ) is the maximum gain (V _MAX ) at the first Frequency is not exceeded, and the resulting gain (V _RES ) is limited to the maximum gain (V _MAX ) when the target gain (V _Z ) exceeds the maximum gain (V _MAX ) at the first frequency, characterized in that when the resulting gain (V _RES ) at the first frequency is limited to the maximum gain (V _MAX ), the gain at the second frequency is automatically raised from the target gain (V _Z ) at the second frequency and a resulting gain (V _RES ) is set at the second frequency, which is above the target gain (V _Z ) at the second frequency and is limited to the maximum gain (V _MAX ) at the second frequency. The method of claim 1, wherein the maximum gain (V _MAX ) and the target gain (V _Z ) are determined in a plurality of frequency bands and the resulting gain (V _RES ) is set in those frequency bands. The method of claim 1 or 2, wherein the determination of the maximum gain (V _MAX ) and the determination of the target gain (V _Z ) and the adjustment of the resulting gain (V _RES ) in the adaptation of the hearing aid (4, 10) by means of an adapter ( 1). The method of claim 1 or 2, wherein the determination of the maximum gain (V _MAX ) and the determination of the target gain (V _Z ) and the adjustment of the resulting gain (V _RES ) during operation of the hearing aid (4, 10) take place. Method according to one of claims 1 to 4, wherein for determining the maximum gain (V _MAX ) an open-loop gain measurement is performed. Method according to one of claims 1 to 5, wherein the choice of the second frequency and the increase of the resulting gain (V _RES ) compared to the target gain (V _Z ) at the second frequency are such that a speech intelligibility in the hearing aid (4, 10) output signal is increased. The method of claim 6, wherein speech intelligibility is increased based on a speech intelligibility model. Method according to one of claims 1 to 7, wherein the selection of the second frequency and the increase of the resulting gain (V _RES ) relative to the target gain (V _Z ) at the second frequency are such that by limiting the gain at the first frequency and the increase in the gain at the second frequency, the perceived by a hearing aid wearer volume of the output from the hearing aid (4, 10) output signal is at most slightly increased. The method of claim 8, wherein the volume is determined by means of a loudness model. Adaptation device for adapting a hearing aid device (4, 10) to the individual hearing loss of a hearing aid wearer and for carrying out a method according to one of claims 1 to 9. Hearing aid (4, 10) with at least one input transducer (11) for receiving an input signal and conversion to an audio signal, a signal processing unit (12-19) for processing and amplifying the audio signal and an output transducer (20) for generating a sound from a user Signal perceptible output signal, characterized by means (16) for storing data regarding a maximum gain (V _MAX ) of the audio signal at at least a first and a second frequency, means for automatically determining a target gain (V _Z ) in the first and the second Frequency, means for limiting the gain at the first frequency to the maximum gain (V _MAX ) when the target gain (V _Z ) exceeds the maximum gain (V _MAX ) at the first frequency, means for automatically increasing the gain over the target gain ( V _Z ) at the second frequency when the gain at the first Frequency is limited, such that an adjustable in the hearing aid resulting gain (V _RES ) does not exceed the maximum gain (V _MAX ) at the second frequency.

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