EP1274278B1 - Method of operating a digital programmable hearing device and a corresponding digital programmable hearing device - Google Patents

Abstract

A maximum amplification transmission characteristic of an amplified audio signal is set over a frequency range. An amplification modulation value in the frequency range is determined from a parameter set by a hearing aid user. A final amplification value at a preset frequency is determined based on the amplification modulation value and the final value is limited to maximum gain for the preset frequency. <??>An Independent claim is included for digital programmable hearing aid.

Description

The invention relates to a method for operating a digital programmable hearing aid with an input transducer for receiving an input signal and conversion into an audio signal, a signal processing unit for processing and frequency-dependent amplification of the audio signal and an output transducer. Furthermore, the invention relates to a digital programmable hearing aid for carrying out the method.

Acoustic feedbacks are common in hearing aids, especially if they are high gain hearing aids. These feedbacks are expressed in strong feedback oscillations of a given frequency (feedback). This "whistling" is usually very unpleasant for both the hearing aid wearer and for persons in his immediate vicinity.

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, in order for the typical "whistling" - usually at a dominant frequency - comes, but two other conditions must be met. The so-called loop gain of the system, i. the product of the hearing aid gain and the attenuation of the feedback path must be greater than 1. 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 the hearing aid gain so that the loop gain remains below the critical limit even in adverse situations. Of the The decisive disadvantage, however, is that the hearing aid reinforcement required for severe deafness can no longer be achieved by this limitation.

The typical feedback for pipes is usually at relatively high frequencies. There are known hearing aids with a volume control actuatable by the hearing aid wearer, e.g. the hearing aid model "Swing" of Siemens Audiologische Technik GmbH, by which the amplification of an audio signal can be changed. In this case, the increase or decrease in the amplification of the audio signal as a function of the frequency, wherein at a low gain almost the entire transmission range of the hearing aid is equally amplified and at a high gain higher frequencies are less strongly amplified as lower frequencies. The frequency-dependent gain in accordance with the volume control is static.

From the DE 196 24 092 A1 An amplifier circuit for analog or digital hearing aids is known. For better adaptation to the hearing of a subject, the circuit comprises at least two compression circuits as subcircuits, which overlap differently and wherein a resulting gain characteristic V can be generated, wherein the compression ratio decreases with increasing input level continuously or at defined time intervals.

From the DE 196 19 312 A1 For example, an amplifier circuit for a hearing aid is known in which an input signal has a signal level which is divided into individual frequency band-specific partial signal paths (channels).

From the EP 0 250 679 B1 a hearing aid with a storage means for storing coefficients with respect to a filter frequency response is known.

From the US 5,303,306 a hearing aid with a basic setting is known, wherein parameters of the basic setting can be changed by pressing buttons on a remote control. In this way, cut-off frequencies, the gain in individual frequency bands, the roll-off or the volume adjustment can be adjusted.

Object of the present invention is to provide a method for operating a hearing aid and a hearing aid that allow a wide frequency response.

This object is achieved in a method for operating a digital programmable 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 frequency-dependent amplification of the audio signal and an output transducer in that a transfer characteristic of a maximum gain of the audio signal via the frequency is adjustable and at least one gain change value is determined at least in a frequency range from an adjustable by the hearing aid wearer parameters and / or a signal automatically generated by the signal processing unit, wherein at the respective frequency to a gain output value taking into account the gain change value, a gain end value is determined and this is limited to the maximum gain, giving an effective system gain for each frequency results.

The digital programmable hearing aid part of the object is achieved according to claim 9.

The hearing aid according to the invention is, for example, a hearing aid worn behind the ear, a hearing aid that can be worn in the ear, an implantable hearing aid or a pocket hearing aid. Furthermore, the hearing device according to the invention may also be part of a plurality of devices for supplying a hearing-impaired hearing aid system, eg 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 and a device on the body portable processor unit. The hearing aid comprises an input transducer for receiving an input signal. Typically, the input transducer is a microphone that picks up an acoustic signal and converts it into an electrical audio signal. However, as input transducers are also units into consideration, which have a coil or an antenna and receive an electromagnetic signal and convert it into an electrical audio signal. The hearing aid according to the invention further comprises a signal processing unit for processing and frequency-dependent amplification of the audio signal. The signal processing in the hearing aid by means of a digital signal processor (DSP), the operation of which can be influenced by means of transferable to the hearing aid programs or parameters. As a result, the mode of operation of the signal processing unit can be adapted to the individual hearing loss of a hearing aid wearer and to the current hearing situation in which the hearing aid is currently being operated. The thus changed audio signal is finally fed to an output transducer. This is usually designed as a handset that converts the electrical audio signal into an acoustic signal. However, other embodiments are also possible here, for example, an implantable output transducer, which is directly connected to a ossicle and this stimulates to vibrate.

In the context of the invention, an audio signal in the narrower sense is understood to mean an electrical signal which emerges from the signal recorded by the input transducer and is transmitted by the hearing aid. It usually contains information in the audible frequency range. The audio signal may be present in the hearing aid in analog or digital form, wherein both signal waveforms may occur simultaneously in the signal path of the hearing aid. In the broader sense, an audio signal in the invention is understood to mean also an electrical signal which emerges from the audio signal in the narrower sense by further processing, for example by filtering, transformation, etc.

The invention provides that a transmission characteristic of a maximum amplification of the audio signal can be adjusted over the frequency, i. For example, in the adaptation of the hearing aid by the acoustician is freely configurable. Furthermore, at least one gain output value is stored in the hearing aid, which is preferably also adjustable by the acoustician. The amplification output value may be constant for the entire transmittable frequency range of the hearing aid or else within a respective frequency band of the hearing aid. Advantageously, however, (within certain limits) an arbitrary gain output value can be set for each frequency, so that a transfer characteristic of a normal amplification of the audio signal over the frequency is freely configurable.

The normal gain setting determines the factor by which an input audio signal with a certain signal amplitude is amplified as a function of the frequency. If the hearing device has a volume control that can be actuated by the hearing aid wearer, then this is preferably in a middle position for setting the normal amplification, so that the hearing aid wearer has the possibility of increasing or reducing the amplification, starting from this basic setting. The adjustment of the normal gain as well as the maximum gain can be done both with respect to hearing aid specific and the individual hearing aid wearer concerning aspects. If, for example, when fitting a hearing device to a user, it is found that more feedback whistling occurs at a certain frequency and a certain gain, the maximum gain in this frequency range is set below this gain.

The transfer characteristics are for a certain frequency range and for a certain value range of the gain preferably freely configurable. The transmission characteristics can be determined by means of a suitable fitting software as such and transmitted to the hearing aid, but they can also be determined only by specifying some frequency and gain value pairs. Furthermore, in addition to a continuous course, a discontinuous course of the transfer characteristics is possible.

The actual amplification of an audio signal in a hearing aid, in addition to the frequency depends on a number of other factors. Such factors may be parameters derived from the momentary adjustment of the volume control on the hearing aid, the amplitude of the input signal, or a signal analysis in the signal processing unit of the hearing aid. The latter are determined, for example, by algorithms for situation analysis, noise suppression or automatic gain control (AGC). In general, therefore, in modern hearing aids, a number of control functions have an influence on the instantaneous amplification.

Starting from the gain output value or from the characteristic of the normal gain over the frequency, all influencing factors with regard to the gain for the respective frequency are now considered according to the invention. For example, if the current volume setting causes a 10 dB increase in audio signal and a noise suppression algorithm causes a 15 dB decrease, a total gain change value of -5 dB results. Unlike in this example, the gain change value may also be a factor by which the gain output value is multiplied. Taking into account all the influencing factors on the gain (gain change values) at the respective frequency, the gain output value is then determined from the gain output value. If the amplification end value at the respective frequency exceeds the preset maximum amplification, this becomes the maximum amplification limited. The effective system gain is thus always less than or equal to the maximum gain.

The invention offers the advantage that for a given hearing aid, almost any normal gain as well as almost any maximum amplification can be set. The signal processing in the hearing aid can thereby be better adapted both to hearing aid-specific conditions and to the individual hearing damage of a hearing aid wearer. Furthermore, the invention has the advantage that several influencing factors acting on the amplification at the same time (e.g., the current position of the volume control, gain variation by a signal processing algorithm, maximum gain set) are better taken into account.

An embodiment of the invention provides that the signal processing takes place in a plurality of parallel frequency channels of the signal processing unit and the transmission characteristic of the normal amplification of the audio signal over the frequency and / or the transmission characteristic of the maximum amplification of the audio signal over the frequency for the respective channel are separately adjustable , The division of the audible frequency range into multiple channels facilitates the adaptation of a hearing aid when a characteristic channel (ie a certain frequency range) relevant parameters for this channel are considered to be constant. Such characteristics for a particular channel may be the threshold of hearing, the discomfort threshold, but also the normal gain or maximum gain. For identification only the indication of a value for the respective channel is required.

• Figur 1 die Realisierung eines Roll-offs bei einem analogen Hörgerät nach dem Stand der Technik,
• Figur 2 Übertragungskennlinien der Verstärkung über der Frequenz bei einem analogen Hörgerät nach dem Stand der Technik,
• Figur 3 die Verstärkung über der Frequenz bei einem Hörgerät gemäß der Erfindung,
• Figur 4 ein Mehrkanal-Hörgerät mit Roll-off-Logik in den einzelnen Kanälen und

Further details of the invention will be described below with reference to embodiments. Showing:

• FIG. 1 the realization of a roll-off in an analog hearing aid according to the prior art,
• FIG. 2 Transmission gain vs. frequency characteristics in a prior art analog hearing aid;
• FIG. 3 the gain over the frequency in a hearing aid according to the invention,
• FIG. 4 a multi-channel hearing aid with roll-off logic in each channel and

FIG. 5 a multi-channel hearing aid with overall roll-off logic.

FIG. 1 shows the circuitry realization of a roll-off in a hearing aid with analog signal processing. In this case, the amplifier circuit comprises an operational amplifier OA, which is connected to an input resistor R1 and an RC element of a potentiometer R2 and a capacitor C in the feedback path. The potentiometer R2 can be used to change the amplification and thus the volume setting on the hearing aid. However, as the gain increases, so does the cutoff frequency (the knee point) at which the gain decreases with increasing frequency.

FIG. 2 shows the gain V over the frequency f for different potentiometer settings of the amplifier circuit according to FIG. 1 , The characteristic 1 shows the gain V over the frequency f at maximum volume setting. At this setting, the resistance of the potentiometer R2 is greatest. Up to a cutoff frequency, the gain is constant, above the cutoff frequency the gain decreases linearly with increasing frequency. The curves 2 and 3 show the gain over the frequency for the normal position (characteristic 2) or the minimum position (Characteristic 3) of the volume control. How out FIG. 2 It can also be seen that, as the gain decreases, there is an increase in the cut-off frequency at which an increase in the gain of the higher frequencies occurs.

The adjustment of the amplification in hearing aids in the manner described above is due to the fact that increasingly undesirable feedback whistling (feedback) occurs, in particular with high amplification and high frequencies. The gain reduction of the high frequencies counteracts this. The higher the gain, the greater the likelihood of feedback whistles and therefore the onset of subsidence at lower frequencies.

The above-described method for gain reduction is relatively rigid and offers little leeway for individual or device-specific adaptation. In modern hearing aids, the effective amplification often depends on other factors in addition to the setting of the volume control. In this case, a signal analysis, which is carried out in the signal processing unit, based on a number of different algorithms, which can also run in parallel. These algorithms, by analyzing the input signal, provide automatic gain control (AGC = A utomatic G ain C ontrol) or affect the gain through the automatic tuning of a hearing program as a result of situation analysis. Furthermore, in the case of a hearing aid, it is also possible, for example, to provide an algorithm for noise suppression which, given a detected noise, reduces the amplification in a broadband manner by a specific amount. This process is exemplary in FIG. 2 illustrated. The gain reduction by a certain amount causes a parallel shift of the preset characteristic of the normal gain 2 by just this amount. In FIG. 2 this is illustrated by the characteristic 4 and the arrow 5. There, starting from the setting of the volume control in the normal position (characteristic curve 2), the amplification automatically reduces the signal processing unit so that the effective system gain illustrated by characteristic 4 results. How out FIG. 2 Furthermore, it can be seen that the already reduced gain above the frequency F1 is again reduced.

In FIG. 3 the gain versus frequency is illustrated in a hearing aid according to the invention. In this case, a characteristic of the normal gain 6 is largely freely configurable in the frequency / gain diagram. This characteristic can be determined for example by a hearing care professional and transmitted to the hearing aid. If the hearing device in question has a volume control, this characteristic curve is preferably associated with a middle position of the volume control, so that the hearing device wearer can change the amplification from the normal amplification by actuation of the volume control both to higher amplifications and to lower amplifications.

Furthermore, in the hearing aid according to the invention, a characteristic of the maximum gain 7 can be stored. These can also be determined by the acoustician during the adaptation of the hearing device and transferred to it during the programming of the hearing device. If a change in the gain occurs in a hearing aid according to the invention, starting from the preset normal gain, this results in an effective gain, as exemplified in FIG FIG. 3 is illustrated by the characteristic 8. Starting from the characteristic curve of the normal gain 6, a parallel reduction of the gain characteristic is first effected by a certain amount, for example -10 dB, and the lowered characteristic curve is then limited again to the characteristic of the maximum gain 7 from a frequency F2. As a result, even at high frequencies always only a one-time reduction, as opposed to FIG. 2 , which illustrates the same situation in a conventional hearing aid and in the characteristic 4 above the frequency F1 a two-fold decrease in gain occurred.

The FIGS. 4 and 5 show by way of example in the block diagram hearing aids with a gain control according to the invention. As an input transducer in the hearing aid 10 according to FIG. 4 serves a microphone 11, which receives an acoustic signal and converts into an electrical signal. 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 divided into several frequency bands (channels) by means of the filter bank 13. The audio signals of the individual channels are first fed to signal processing units 14A-14E, in which the audio signals are filtered differently, for example for adaptation to the individual deafness of a hearing device wearer. 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 roll-off logic 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 from a default setting of the gain by the hearing aid manufacturer and when the acoustic device adjusts the hearing aid. Similarly, 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 in the embodiment is shown, the roll-off logic units 15A-15E further the current setting of a volume control 17 may be supplied. From the parameters supplied to the roll-off logic units 15A-15E, they determine a certain 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 (3rd gain change value) due to a detected spurious signal, so that taking into account all the gain change values, a total gain change value of -20 dB and thus an amplification end value of 30 dB result. If this amplification end value at the respective frequency is less than or equal to the maximum amplification, then this amplification is also the effective system amplification. Otherwise, the resulting gain is limited to the maximum gain, so that the latter forms the effective system gain. The effective system gain thus determined for the individual channels now controls gain elements 18A-18E for amplifying the processed audio signals in the individual channels. Subsequently, the audio signals of the individual channels are brought together again and, if necessary, after a signal post-processing in the signal post-processing unit 19, in which, for example, a filtering, an amplification and a D / A conversion takes place, a receiver 20 is supplied. This converts the processed electrical audio signal back into an acoustic signal that is delivered into the auditory canal of the hearing aid wearer.

The invention can be implemented in circuit technology in a number of different ways. Another embodiment of this shows FIG. 5 , In this embodiment as well, a hearing aid 30 is connected via a microphone 31 Acoustic input signal recorded and converted into an electrical audio signal, which is supplied to a preamplifier and A / D converter unit 32. According to the previous embodiment, the processing of the audio signal in a plurality of parallel channels, which are divided by means of a filter bank 33, also takes place here. Unlike in the embodiment described above, however, the parameters determined in individual signal processing units 34A-34E are supplied to a common roll-off logic unit 35. Into these, parameters stored in a memory 36 continue to characterize the normal gain as well as the maximum gain. Likewise, the current setting of the volume control 37 flows in as well. From all parameters entering the roll-off logic unit 35, this parameter calculates to control a variable filter 41, so that in this embodiment too, first all amplification requirements are fulfilled by the reinforcing elements 38A-38E, but in contrast to the aforementioned embodiment according to FIGS Merging the audio signals of the individual channels, the limitation to the maximum gain by means of the variable filter 41 is realized, which in turn is controlled by the roll-off logic unit 35. Signal processing in a signal post-processing unit and the output of the processed audio signal via a receiver 40 may also take place in this exemplary embodiment.

Claims (11)

1. Method for operating a digital, programmable hearing aid (10, 30) with at least one input transducer for recording an input signal and converting it into an audio signal, a signal-processing unit (14A-14E; 34A-34E) for processing and frequency-dependent amplification of the audio signal, and an output transducer, characterized in that a transmission characteristic of a maximum gain (7) of the audio signal over frequency can be set and at least one gain modification value is established, in at least one frequency range, from a parameter that can be set by the hearing-aid wearer and/or a parameter that is automatically generated by the signal-processing unit, with a gain final value being established at the respective frequency for a gain initial value, taking account of a gain modification value, and this final gain value being limited to the maximum gain such that this results in an effective system gain for the respective frequency.
2. Method according to Claim 1, characterized in that a transmission characteristic of a normal gain (6) over frequency can be set, which is used to decide the gain initial value at each frequency.
3. Method according to Claim 1 or 2, characterized in that the parameter that can be set by the hearing-aid wearer is set by means of a volume control (17, 37) that can be actuated by the hearing-aid wearer.
4. Method according to one of Claims 1 to 3, characterized in that the parameter automatically generated by the signal-processing unit emerges from an algorithm for situation analysis and/or noise removal and/or compression.
5. Method according to one of Claims 1 to 4, characterized in that gain values for characterizing the transmission characteristic of the normal gain (6) of the audio signal over frequency and also for characterizing the transmission characteristic of the maximum gain (7) of the audio signal over frequency are stored in a memory.
6. Method according to one of Claims 1 to 5, characterized in that gain limiting for higher frequencies is introduced by means of the transmission characteristic of the maximum gain (7) of the audio signal over frequency.
7. Method according to one of Claims 1 to 6, characterized in that the signal processing takes place in a plurality of parallel frequency channels in the signal-processing unit (14A-14E; 34A-34E) and the transmission characteristic of the normal gain (6) of the audio signal over frequency and/or the transmission characteristic of the maximum gain (7) of the audio signal over frequency can be set separately for the respective channel.
8. Method according to Claim 7, characterized in that a constant normal gain and/or a constant maximum gain is set separately for each channel.
9. Digital, programmable hearing aid (10, 30) for carrying out a method according to one of Claims 1 to 8, comprising at least one input transducer for recording an input signal and converting it into an audio signal, a signal-processing unit (14A-14E; 34A-34E) for processing and frequency-dependent amplification of the audio signal, a memory (16, 36) for storing gain values for characterizing a transmission characteristic of a maximum gain (7) of the audio signal over frequency, and an output transducer, with the signal-processing unit being designed such that the transmission characteristic of a maximum gain (7) of the audio signal over frequency can be set and at least one gain modification value is established, in at least one frequency range, from a parameter that can be set by the hearing-aid wearer and/or a parameter that is automatically generated by the signal-processing unit, with a gain final value being established at the respective frequency for a gain initial value, taking account of a gain modification value, and this final gain value being limited to the maximum gain such that this results in an effective system gain for the respective frequency.
10. Digital, programmable hearing aid (10, 30) according to Claim 9, furthermore comprising a memory (16, 36) for storing gain values for characterizing a transmission characteristic of a normal gain (6) of the audio signal over frequency.
11. Digital, programmable hearing aid (10, 30) according to Claim 9 or 10, which comprises at least one volume controller (17, 37) that can be set by the hearing-aid wearer and a signal-processing unit (14A-14E; 34A-34E) with executable algorithms for situation analysis and/or noise removal and/or compression, furthermore comprising at least one roll-off-logic unit (15A-15E; 35), which establishes an effective system gain for the respective frequency from the normal gain, the maximum gain and from parameters emerging from setting the volume control (17, 37) and from the algorithms for situation analysis and/or noise removal and/or compression.

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