EP3454572A1 - Method for detection of a defect in a listening instrument - Google Patents

Abstract

The invention specifies a method for detecting a defect in a hearing instrument (1), which has at least one first input transducer (4) and at least one output transducer (8), wherein a first transfer function (T1) of a first acoustic system (26), comprising the Output transducer (8) and the first input transducer (4), is determined, wherein at least a first reference function (R1) for the first transfer function (T1) is determined, wherein the first transfer function (T1) with the first reference function (R1) is compared , and wherein based on the comparison, a defect in the hearing instrument (1) is detected. The invention also mentions a hearing instrument (1) having at least a first input transducer (4) and an output transducer (8), which is set up to carry out the method.

Description

The invention relates to a method for detecting a defect in a hearing instrument, which has at least a first input transducer and at least one output transducer.

In a hearing aid, sound signals of the environment are converted by one or more input transducers into electrical signals, which are signaled by a signal processor or the like. be further processed and then converted by an output transducer back into an output sound signal. The output sound signal is fed to the ear of a user who usually has a hearing impairment. Thus, the processing of the electrical signals in the signal processor under the proviso to compensate for this impairment by appropriate treatment as possible.

For this purpose, in particular a faultless functionality of the electro-acoustic hardware components, so the input transducer and the output transducer is required. These components in hearing aids can usually lose part of their performance with increasing operating time, ie, at comparable sound pressures produce the input transducer electrical signals of increasingly lower amplitude, while the output transducer from a normalized test signal over time generates an ever lower sound pressure. This loss of performance, which is primarily due to the wear of the electro-acoustic components, is further intensified by the fact that the components in the hearing aid, when worn in the ear, are exposed to the effects of moisture or sebum. A malfunction of the Hearing aid is therefore often due to a corresponding damage or impairment of one of the electro-acoustic hardware components.

While a total failure of one of these components-that is, one of the input transducers or the output transducers-is easily recognizable to the user of the hearing aid, only a gradual decrease in performance, such as that seen in e.g. may be given by attenuation or attenuation in a particular frequency range, often difficult to detect by the user or by a hearing care professional without a specific measurement. This results in a permanent operation of the hearing aid to a lack of correcting the user for his hearing impairment, which may also affect the participation in his environment and his concentration due to the thus reduced speech intelligibility.

However, such problems with electroacoustic hardware components can also be found in other hearing instruments such as e.g. Mobile phones occur. Again, a defect in an input transducer for the user itself is difficult to see because he can not even check the input signal generated from his own language itself, and thus relies on statements to his interlocutors. Also, a broadband attenuation in the output transducer is difficult for the user to recognize, especially as in mobile phones, the tendency of the user to take into account, shortcomings in the output sound signal usually attributable to insufficient signal transmission through the mobile network. Moreover, mobile phones are also worn on the body, e.g. in a trouser or jacket pocket, potentially exposed to moisture and shock, which can affect the electroacoustic components.

Recognizing a possible deterioration of the functionality over a longer period of operation is thus a general problem of hearing instruments with electro-acoustic components.

The invention is therefore based on the object of specifying a method for detecting a defect in a hearing instrument, which with high reliability is as simple as possible, and for the implementation itself no additional conditions to the hearing instrument, and in particular requires no further equipment.

The above object is achieved by a method for detecting a defect in a hearing instrument, which has at least a first input transducer and at least one output transducer, wherein a first transfer function of a first acoustic system comprising the output transducer and the first input transducer, is determined at least one first reference function for the first transfer function of the first acoustic system is determined, wherein the first transfer function of the first acoustic system is compared with the first reference function, and wherein a defect in the hearing instrument is detected on the basis of the comparison. Advantageous and partly inventive in themselves embodiments are the subject of the dependent claims and the following description.

In this case, a hearing instrument is generally understood to be any device in which a sound signal from the environment is converted by an electroacoustic input transducer into an internal electrical signal, and in which an output sound signal is generated from an electrical output signal of the device by an electroacoustic output transducer, ie in particular Hearing aid and a mobile phone.

Preferably, in this case, the hearing instrument also has a signal processing unit, wherein in operation the first input transducer from a sound signal of the environment generates a first input signal which is supplied to the signal processing unit, and wherein the signal processing unit outputs an output signal in operation, which is converted by the output transducer into an output sound signal , The output signal may be based on the input signal, as is the case in a hearing aid, or on a signal received by an antenna, as is the case in a mobile telephone. In the latter case, the signal processing unit may in particular be adapted to process the input signal for transmission by a transmitting antenna - eg by corresponding coding in a transmission protocol - and to decode a signal received at a receiving antenna and to convert it into an output signal.

The determination of the first reference function can be carried out in particular before determining the current first transfer function. In this case, the first reference function may in particular also be "trivial", that is to say given by a frequency-independent limit value for the first transfer function or for the amount of the first transfer function. Preferably, however, the reference function is non-trivial, ie frequency-dependent.

By determining a transfer function for an acoustic system comprising the first input transducer and the output transducer, advantageous information is provided, in particular for the detection of defects in these components. By using the transfer function, this information is also available in frequency-resolved form, which simplifies analysis for a defect. The first transfer function is preferably determined without the use of an external sound generator for stimulating or checking the first input transducer or an additional external microphone for checking the output transducer. This can be achieved by a suitable choice of the first acoustic system.

In this case, the first reference function is to be determined in such a way that it can serve as a reference for the first transfer function when the hearing instrument is fully functional, ie without defects. By comparing the first transfer function with the first reference function, it is now possible to identify, for example, those frequency ranges in which the functioning of the hearing instrument is impaired. For a more precise localization of the defect, the first transfer function and the first reference function can now be examined, in particular in the frequency domain and the time domain. This provides an additional information content and can allow conclusions to be drawn as to which component a defect is exactly present, ie whether the defect is present at the first input transducer or at the output transducer. A defect of the output transducer can occur in a pulse response of the first transfer function which is considerably weakened compared to the values of the first reference function, while a defect of the input transducer may, inter alia, have an impulse response of the first transfer function which is time-displaced with respect to the values of the first reference function.

Conveniently, as the first transfer function of the first acoustic system, the open signal loop transfer function is determined, the open signal loop being formed from the output transducer, an acoustic feedback path from the output transducer to the first input transducer, and the first input transducer. The transfer function of the open signal loop can be determined in a particularly simple manner, for example by a suitable test signal, which is converted by the output transducer into a test sound signal, and an analysis of the signal component of the test signal in a first input signal generated by the first input transducer, and from there to the first input transducer estimate incoming portion of the test sound signal. Another advantage of using the open signal loop as the first acoustic system, and thus the use of the open signal loop transfer function as the first transfer function, is that the first input transducer and the output transducer are completely covered by this system so that no additional sound generators and no additional sound generators are included Measuring apparatus are required.

In this case, a further transfer function of a closed signal loop is preferably determined, and from this the transfer function of the open signal loop is determined as the first transfer function, wherein the closed signal loop is formed from the output transducer, an acoustic feedback path from the output transducer to the first input transducer, the first input transducer and a signal processing path from first input converter to output transducer. The closed signal loop is thus formed by the open signal loop, which is closed by the signal processing path from the input transducer to the output transducer. This is advantageous, in particular, in a hearing instrument designed as a hearing aid, since there a transfer function of the closed signal loop is often already connected in the context of the suppression an acoustic feedback is determined, and thus no further measurements are required or additional functions are to be implemented.

Preferably, the transfer function of the closed signal loop is determined by an adaptive filter, wherein the open signal loop is determined on the basis of the closed signal loop taking into account signal processing taking place along the signal processing path. This can be achieved in particular by correcting the transfer function of the closed signal loop determined by the adaptive filter by a corresponding transfer function of the internal signal processing processes which take place along the signal processing path of the hearing instrument, since these signal processing processes are assumed to be completely known.

Advantageously, the adaptive filter is used in the hearing instrument for suppressing acoustic feedback via the acoustic feedback path from the output transducer to the first input transducer. This means, in particular, that the adaptive filter is provided and set up for feedback suppression as required during the intended use of the hearing instrument, and that the adaptive filter can be used in connection with the detection of a defect in the hearing instrument by accessing the transfer function of the closed signal loop which was determined for the purpose of suppressing the feedback. Optionally, the adaptive filter may also be operated in a dedicated mode for detecting a hearing instrument defect.

Alternatively, a test signal is fed to the output transducer, a test sound signal is generated by the output transducer from the test sound signal comprising the test sound signal, and the transfer function of the open signal loop is determined as the first transfer function from the input signal and the test signal , This means that the transfer function of the open signal loop is determined by a direct measurement. In particular, in this case the spectral power density of the test signal is constant over the frequency, the test signal is So a "white noise". A direct measurement of the transfer function of the open signal loop can thus be realized particularly easily. This also applies to the case in which the hearing instrument is provided by a mobile phone, since for this purpose the loudspeaker only has to generate the test sound signal, and only the proportion arriving therefrom must be measured on the microphone.

In particular, the first transfer function is determined at predetermined intervals, ie either regularly or as a function of the respective duration of the operating phases. Also, the first transfer function can be determined by a user input. In particular, the user information can in this case activate the complete method for detecting a defect, for example if the user has the subjective impression of an existing malfunction in the hearing instrument and would like to obtain objective clarity thereon. Also, the complete method of detecting a defect may be performed regularly or as a function of the duration of the operating phases, for example, as part of a maintenance program or the like. respectively.

In an advantageous embodiment, a cross-correlation is used for the comparison of the first transfer function with the first reference function. The cross-correlation can in particular be formed from the first transfer function and the first reference function in the frequency domain and / or from the first transfer function and the first reference function in the time domain, in which the impulse response of the first acoustic system is indicated. The cross-correlation is used in particular as an additional criterion for checking deviations of the first transfer function to the first reference function. In particular, the corresponding correlation coefficient can be used. This has the advantage that in the case of a frequency band-wise deviation between the first transfer function and the first reference function, the degree of deviation is difficult to quantify and, in particular, difficult to set in relation to other scenarios. The correlation coefficient for this purpose provides a single value producing such comparability.

Expediently, the first reference function is determined from a measurement of the first transfer function under normalized conditions. In particular, this can be done for a hearing aid at a hearing care professional. Such a measurement is particularly easy to implement in the already performed fitting with. With a mobile phone, such a measurement is possible with the manufacturer or even with a qualified distributor.

Alternatively, the first reference function may be determined from temporally averaging a plurality of values of the first transfer function at different times. The values at a plurality of points in time can be determined in particular by a regular determination of the values in a given operating interval after commissioning, e.g. in the first days. This is based on the assumption that the hearing instrument is still fully functional at startup, and therefore the initially determined values of the first transfer function are suitable as a basis for the first reference function, whereby for a true reference, irrespective of the respective conditions at the time at which the value has been determined, averaging over several values is advantageous. This procedure is particularly advantageous when a direct measurement of the first transfer function under normalized conditions is not possible - for example, if during fitting of a hearing aid no fitting is provided to a hearing care professional.

Advantageously, the first transfer function is determined from a temporal averaging of a plurality of values of the transfer function of the open signal loop. This makes it possible to compensate for short-term fluctuations. In this case, the temporal averaging preferably includes values which reflect the current status of the hearing instrument as accurately as possible, which can be achieved in particular by a significant weighting of the latest values. The determination of the values of the transfer function of the open signal loop can take place in the background over a longer period of time, and the determination of the first transfer function from these values then takes place via a decreasing weighting of the values during averaging.

Preferably, a defect of the first input transducer and / or the output transducer is detected. For the detection of defects in these components, the method described is particularly suitable.

Conveniently, a measure of a correlation between the first transfer function and the first reference function is determined, wherein the defect is detected on the basis of the degree of correlation. As a measure of the correlation here, for example, a cross-correlation can be used.

Alternatively or additionally, a first polynomial approximating the first transfer function and a first reference polynomial approximating the first reference function may be determined, the defect being detected by a coefficient comparison from the first polynomial and the first reference polynomial. In this case, for example, a threshold value for the deviation of the polynomial coefficients from each other can be predetermined, above which it is concluded that there is a defect in the hearing instrument. The threshold value can be selected differently for each of the different orders of Polynomialkoeffizieten. In particular, as a criterion for a defect in the hearing instrument, in addition to said coefficient comparison, said measure for the correlation of said transfer functions can also be used.
It proves to be further advantageous if a second transfer function of a second acoustic system comprising the output transducer and a second input transducer of the hearing instrument is determined, at least one second reference function for the second transfer function is determined, and the second transfer function is compared with the second reference function , and based on the comparison of the first transfer function with the first reference function and based on the comparison of the second transfer function with the second reference function, a defect in the hearing instrument is detected. On the one hand, this is advantageous for hearing instruments which have a second input transducer, that is, for example, certain embodiments of hearing aids.

In particular, a comparison of the first transfer function with the second transfer function for detecting a defect in the hearing instrument is additionally used. On the other hand, this comparison also allows easier localization of the defect. Roughly speaking, there are at least three possibilities for a defect in electro-acoustic hardware: the two input transducers and the output transducer. The aforementioned comparisons of the transfer function with the corresponding reference function relate either to an input transducer and the output transducer, or both input transducers, since the contribution of the output transducer can be eliminated in a comparison of the first and second transfer functions, for example by simple subtraction.

In particular, the first and the second transfer function can be compared with the respectively associated first or second reference function and also with each other on the basis of a measure for the correlation of the transfer and / or reference functions to be compared. Alternatively or additionally, two transfer and / or reference functions to be compared can each be approximated by polymomes, and a comparison of the relevant polynomial coefficients can be used for a comparison of said functions.

The determination of the second reference function can be carried out in particular before the determination of the current second transfer function. In this case, the second reference function may in particular also be "trivial", that is to say given by a frequency-independent limit value for the second transfer function or for the amount of the second transfer function. Preferably, however, the reference function is non-trivial, ie frequency-dependent.

Conveniently, in this case, a first limit value, a second limit value and a third limit value are predetermined, wherein a first difference is formed from the first transfer function and the first reference function, wherein a second difference from the second transfer function and the second reference function is formed, wherein a third difference the first transfer function and the second transfer function is formed. A defect on the first input transducer is detected if the first difference is the first limit in at least one frequency range exceeds, without the second difference exceeds the second threshold, and / or a defect in the output transducer is detected, if in each case for the first difference and the second difference frequency ranges exist in which the first limit or the second limit is exceeded, without the third difference exceeds the third limit. In particular, the first limit value and the second limit value are identical here. This embodiment is particularly easy to implement due to the low complexity of the arithmetic operations used.

The invention further mentions a hearing instrument with at least a first input transducer and an output transducer, which is set up to carry out the method described above. The advantages stated for the method and its further developments can be transferred analogously to the hearing instrument. Preferably, the hearing instrument for carrying out the method comprises a correspondingly established control unit. This can for example also be implemented by appropriate command blocks within a signal processing unit of the hearing instrument.

In a particularly advantageous embodiment, the hearing instrument is designed as a hearing aid. Especially for the input and output transducers used in hearing aids, as well as possible environmental influences to which a hearing aid and its components are exposed during operation, said method is particularly useful to be able to detect a defect without a complex measurement in a hearing care professional.

Fig. 1

in einem Blockschaltbild ein Hörgerät, in welchem ein Verfahren zum Erkennen von Defekten einzelner Komponenten implementiert ist,

Fig. 2

in drei Frequenzbanddiagrammen für ein störungsfreies Hörgerät die Vergleiche von zwei Transferfunktionen mit den zugehörigen Referenzfunktionen sowie miteinander,

Fig. 3

in drei Frequenzbanddiagrammen für ein Hörgerät mit einem defekten Eingangswandler die Vergleiche von zwei Transferfunktionen mit den zugehörigen Referenzfunktionen sowie miteinander,

Fig. 4

in drei Frequenzbanddiagrammen für ein Hörgerät mit einem defekten Ausgangswandler die Vergleiche von zwei Transferfunktionen mit den zugehörigen Referenzfunktionen sowie miteinander,

Fig. 5

jeweils in der Frequenz- und in der Zeit-Domäne die Transferfunktionen zweier offener Signalschleifen eines störungsfreien Hörgerätes, sowie die zugehörigen Referenzfunktionen,

Fig. 6

jeweils in der Frequenz- und in der Zeit-Domäne die Transferfunktionen zweier offener Signalschleifen eines Hörgerätes mit einem defekten Eingangswandler, sowie die zugehörigen Referenzfunktionen,

Fig. 7

jeweils in der Frequenz- und in der Zeit-Domäne die Transferfunktionen zweier offener Signalschleifen eines Hörgerätes mit einem defekten Ausgangswandler, sowie die zugehörigen Referenzfunktionen, und

Fig. 8

in einem Blockschaltbild ein Hörgerät, in welchem eine alternative Ausführungsform des Verfahrens zum Erkennen von Defekten einzelner Komponenten implementiert ist.

An embodiment of the invention will be explained in more detail with reference to a drawing. Here are shown schematically in each case:

Fig. 1

a block diagram of a hearing aid in which a method for detecting defects of individual components is implemented,

Fig. 2

in three frequency band diagrams for a trouble-free hearing aid the comparisons of two transfer functions with the associated reference functions as well as with each other,

Fig. 3

in three frequency band diagrams for a hearing aid with a defective input transducer the comparisons of two transfer functions with the associated reference functions as well as with each other,

Fig. 4

in three frequency band diagrams for a hearing aid with a defective output transducer the comparisons of two transfer functions with the associated reference functions and with each other,

Fig. 5

in each case in the frequency domain and in the time domain, the transfer functions of two open signal loops of an interference-free hearing aid, as well as the associated reference functions,

Fig. 6

in each case in the frequency domain and in the time domain, the transfer functions of two open signal loops of a hearing aid with a defective input transducer, as well as the associated reference functions,

Fig. 7

in each case in the frequency domain and in the time domain, the transfer functions of two open signal loops of a hearing aid with a defective output transducer, as well as the associated reference functions, and

Fig. 8

a block diagram of a hearing aid, in which an alternative embodiment of the method for detecting defects of individual components is implemented.

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

In Fig. 1 is shown schematically in a block diagram a hearing instrument 1, which is designed as a hearing aid 2. The hearing device 2 comprises a first input transducer 4 and a second input transducer 6, which are each formed by a microphone, and an output transducer 8, which is provided by a loudspeaker. The first input transducer 4 and the second input transducer 6 are configured to convert a sound signal, not shown in more detail, into a first input signal 10 and a second input signal 12, respectively. The first input signal 10 and the second input signal 12 are each supplied to a signal processing unit 14 in which the hearing aid-specific processing takes place, ie in particular a frequency band-dependent amplification of the input signals 10, 12 as a function of the hearing impairment of the user of the hearing aid and an improvement of the signal-to-noise ratio. Noise ratio, including using directional microphone. The signal processing unit 14 generates an output signal 16, which is converted by the output transducer 8 in an unspecified output sound signal.

In order to detect a defect at the first input transducer 4, at the second input transducer 6 or at the output transducer 8 as part of the operation of the hearing aid 2, the signal processing unit 14 outputs as output signal 16 a test signal 18, which is converted by the output transducer 8 into a test sound signal 20. In the present case, the test sound signal 20 is essentially given by white noise, ie has a substantially flat frequency spectrum. However, other types of signals, e.g. Sinus tones of different frequencies, chirps, so-called "perfect sweeps" or the like, which allow statements about the broadest possible frequency spectrum, conceivable.

The first input transducer 4 and the second input transducer 6 now each convert the corresponding sound signals into the input signals 10 and 12, and thus also at the respective input transducers 4, 6 via the corresponding acoustic feedback path 22 and 24 from the output transducer 8 to the input transducer 4, 6 incoming portion of the test sound signal 20.

Based on the first input signal 10 and the output signal 8, a first transfer function T1 is determined for a first acoustic system 26, which is formed by the open signal loop from the output transducer 8 via the acoustic feedback path 22 to the first input transducer 4. This can be done on the one hand by a direct measurement of the portion of the test signal 18 in the first input signal 4, or on the other hand via an estimate based on the closed signal loop, which is formed from the first acoustic system 26, ie the open signal loop, and from the signal processing unit 14. The closed signal loop or its transfer function is often available anyway in hearing aids, since it is determined to suppress acoustic feedback via the acoustic feedback path 22.

Furthermore, based on the second input signal 12 and the output signal 8 for a second acoustic system 28, which is formed by the open signal loop from the output transducer 8 via the acoustic feedback path 24 to the second input transducer 6, a second transfer function T2 is determined.

For each of the first transfer function T1 and the second transfer function T2, a first reference function or a second reference function are now stored. This can be done on the one hand by measurements of the first transfer function T1 and the second transfer function T2 under normalized conditions at a hearing care professional, or on the other hand by a time averaging of the respective values of the first transfer function T1 or T2 during the first days after commissioning, since it is assumed may be that at this time the hardware components to be checked still have full functionality.

The respectively currently determined first and second transfer function T1, T2 is now compared with the corresponding reference functions in order to conclude from this that a possible defect of the hardware components can be. This is based on the FIGS. 2 to 4 explained.

In Fig. 2a-2c are each in a frequency band diagram against the frequency f, the first transfer function T1 and the first reference function ( Fig. 2a ), the second transfer function T2 and the second reference function R2 ( Fig. 2b ) as well as the difference between the first transfer function T1 and the second transfer function T2 ( Fig. 2c ). In Fig. 2a remains the first transfer function T1 over the entire frequency range shown within a corridor, which is specified by the first limit g1 of 10 dB. Moreover, the first transfer function T1 does not record any appreciable deviations from the first reference function R1, which represents the undisturbed operation of the hearing aid 2. Also in Fig. 2b shown second transfer function T2 is over the entire frequency range shown within the corridor, which is defined by the second threshold g2 of 10 dB. Likewise, there are no significant deviations from the second reference function R2. The difference T1-T2 of the first and second transfer function T1 or T2 is as based on Fig. 2c within the corridor defined by the third threshold g3. The hearing aid 2 thus operates trouble-free.

In Fig. 3a-3c are the same sizes as shown in Fig. 2a-2c , In the present case, however, for a small frequency range from just below 5 kHz to just below 7 kHz, the first transfer function is outside the corridor defined by the first limit over +/- g1. In the present case, the first reference function is also slightly negative for this area, so that the difference T1-R1 (not shown) is again within the corridor and no seriously noticeable behavior is present. However, the second transfer function T2 has a steadily increasing deviation from the second reference value R2 starting at approximately 2.5 kHz, and above approximately 4.5 kHz is also outside the corridor defined by the second limit value g2. Above approximately 6.5 kHz, the deviation of the second transfer function T2 from the second reference function R2 (whose function curve is essentially of the order of 0 dB to -5 dB, see FIG Fig. 2b ) already 20 dB, and continues to increase monotonically to well over 40 dB at 8 kHz. A comparable course, only with opposite sign, shows up for the in Fig. 3c shown difference of first and second transfer function T1-T2.

It can now be concluded that on the one hand, the first acoustic system 26, consisting of the output transducer 8, the corresponding acoustic feedback path 22 and the first input transducer 4 operates largely trouble-free, but in the second acoustic system 28, formed from the output transducer 8, the acoustic feedback path 24 and the second input transducer 6, a significant defect must be present. The defect is thus attributable to the second input transducer 6.

The undershooting of the negative first limit value -g1 by the first transfer function T1 in FIG Fig. 3a can also be interpreted as an indication that in the first input converter 4, the functionality is already slightly affected, but here - due to the corresponding course of the first reference function - is still no critical behavior.

Im using Fig. 4a-4c As shown, both the first transfer function T1 ( Fig. 4a ) as well as the second transfer function T2 ( Fig. 4b ) are significantly outside the corridor defined by the first and second limit values g1, g2, respectively, and differ significantly from the respective reference functions R1 and R2, the deviation still being over 20 dB in the most favorable case. In the Fig. 4c however, the difference of the first and the second transfer function T1-T2 shown lies within the corridor predetermined by the third limit value g3. This suggests that the defects leading to significant deviations in the two diagrams in Fig. 4a and Fig. 4b lead to be largely eliminated by the difference.

The difference between the first transfer function T1 and the second transfer function T2 essentially gives the differences between the two acoustic feedback paths 22, 24 from the output transducer 8 to the first and second input transducers 4 and 6, respectively, and the differences between the two input transducers 4, 6 themselves again. Moreover, the differences in the acoustic feedback paths 22, 24 may be due at least to the contributions of the output transducer 8 in the first and second transfer functions the significant deviation from the respective reference function R1 or R2 are neglected. This means that, in the present case, the difference T1-T2 of the two transfer functions, which is relatively small in relation to the deviations of the two transfer functions from the respective reference function T1-R1 or T2-R2, can be used to determine a largely interference-free function of the two input transducers 4, 6 , And thus the defect in the output transducer 8 is.

Another way to check the transfer function of the open signal loop from the output transducer 8 via the respective acoustic feedback path 22 and 24 to the corresponding input transducer 4 and 6 with respect to a defective hardware uses the cross-correlation of the respective transfer function T1 or T2 with their corresponding reference function R1 or R2 in the frequency domain and in the time domain.

This is based on the FIGS. 5 to 7 shown. There are in the diagrams of the left column respectively the first transfer function T1 (solid lines) and the first reference function R1 (dashed lines) against the frequency f / Hz (top left diagram) and the corresponding impulse response of the first transfer function T1 and the first reference function R1 is plotted in the time domain against the coefficient number N (bottom left of each diagram). The respective right-hand column shows the corresponding diagrams for the second transfer function T2 (solid lines) and the second reference function R2 (dashed lines).

In Fig. 5 a case is shown, which is based on the Fig. 2a to Fig. 2c described scenario is comparable. The first input transducer 4, the second input transducer 6 and the output transducer 8 work trouble-free. Correspondingly small are the deviations of the two transfer functions T1, T2 from the respective reference function R1, R2 in the frequency and in the Fourier space. The correlation coefficient is 1.0 each except for the cross-correlation between the second transfer function T2 and the second reference function R2 in the time domain, where the correlation is 0.9.

In Fig. 6 a case is shown, which is based on the Fig. 3a to Fig. 3c described scenario is comparable. The first input transducer 4 and the output transducer 8 operate largely trouble-free, even if there are already minor impairments of functionality; the second input transducer 6 has a considerable defect. Correspondingly clear in both diagrams of the right-hand column are the deviations of the second transfer function T2 from the second reference function. In the frequency domain (top right diagram) the correlation coefficient is only 0.3, in the time domain (bottom right diagram) there is even an anti-correlation of -0.7. The correlation coefficients of the first transfer function T1 with the first reference function R1 is 0.8 for both diagrams of the left column, which indicates only a slight impairment.

The in Fig. 7 illustrated case is based on the Fig. 4a to Fig. 4c described scenario comparable. The first input transducer 4 and the second input transducer 6 operate substantially trouble-free; Here, the output transducer 8 has a significant defect. A broadband attenuation of the output power is here visible on the basis of the deviations from the respective reference function R1, R2 both for the first and for the second transfer function T1 or T2 in the frequency domain (upper diagrams). Due to the low frequency dependence of the attenuation of the reproduction in the output transducer 8, the correlation coefficient for the two transfer functions T1, T2 in the frequency domain is 0.8 or 0.7. From this alone, could not conclude on a significant impairment of a hardware function. The differences to the respective reference function R1, R2 become clear here only through the considerations in the time domain (lower diagrams). The correlation coefficients here are -0.4 and -0.5, respectively. This means that in the present case the frequency response for both transfer functions T1, T2 differs essentially only by a translation from the respective reference function R1, R2, while the two impulse responses have significant deviations. From this it can be concluded that the defect of the output transducer 8.

In Fig. 8 is shown schematically in a block diagram of a designed as a hearing aid 2 hearing instrument 1, which in its essential features according to the hearing aid Fig. 1 like. To the hearing aid Fig. 8 To be able to detect a defect at the first input transducer 4, at the second input transducer 6 or at the output transducer 8, no test sound signal 20 is output here by the output transducer 8. Rather, adaptive filters 30, 32 are provided for suppressing acoustic feedback along the acoustic feedback paths 22, 24, respectively. In these adaptive filters 30, 32 in each case a transfer function of the closed signal loops is estimated, which are formed by the first acoustic system 26 and the second acoustic system 28 and the corresponding signal processing in the hearing aid 2, which include the respective adaptive filter 30 and 32, respectively and the signal processing unit 14. By knowing the internal transfer function of the signal processing unit 14, the transfer functions of the first acoustic system 26 and the second acoustic system 28 can be determined on the basis of the adaptive filters 30, 32.

Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by this embodiment. Other variations can be deduced therefrom by those skilled in the art without departing from the scope of the invention.

LIST OF REFERENCE NUMBERS

1

The hearing instrument

2

hearing Aid

4

first input converter

6

second input converter

8th

output transducer

10

first input signal

12

second input signal

14

Signal processing unit

16

output

18

test signal

20

Test sound signal

22

acoustic feedback path

24

acoustic feedback path

26

first acoustic system

28

second acoustic system

30

adaptive filter

32

adaptive filter

g1

first limit

g2

second limit

g3

third limit

R1

first reference function

R2

second reference function

T1

first transfer function

T2

second transfer function

Claims (17)

Method for detecting a defect in a hearing instrument (1) which has at least one first input transducer (4) and at least one output transducer (8),
wherein a first transfer function (T1) of a first acoustic system (26) comprising the output transducer (8) and the first input transducer (4) is determined,
wherein at least one first reference function (R1) is determined for the first transfer function (T1),
wherein the first transfer function (T1) is compared with the first reference function (R1), and
wherein based on the comparison, a defect in the hearing instrument (1) is detected. Method according to claim 1,
wherein as the first transfer function (T1) of the first acoustic system (26) the open signal loop transfer function is determined, the open signal loop being formed from the output transducer (8), an acoustic feedback path (22) from the output transducer (8) to the first input transducer (4), and from the first input transducer (4). Method according to claim 2,
a further transfer function of a closed signal loop formed by the output transducer (8), an acoustic feedback path (22) from the output transducer (8) to the first input transducer (4), the first input transducer (4) and a signal processing path (10, 14, 16) from the first input transducer (4) to the output transducer (8),
and from this the transfer function of the open signal loop is determined as the first transfer function (T1). Method according to claim 3,
wherein the transfer function of the closed signal loop is determined by an adaptive filter (30, 32), and
wherein the open signal loop is determined based on the closed signal loop taking into account signal processing along the signal processing path (10, 14, 16). Method according to claim 4,
wherein the adaptive filter (30, 32) in the hearing aid (1) is used to suppress acoustic feedback via the acoustic feedback path (22) from the output transducer (8) to the first input transducer (4). Method according to claim 2,
wherein a test signal (18) is supplied to the output transducer (8),
wherein a test sound signal (20) is generated by the output transducer (8) from the test signal (18),
wherein a first input signal (10) is generated by the first input transducer (4) from an input sound comprising the test sound signal (20),
and wherein the transfer function of the open signal loop is determined as the first transfer function (T1) from the first input signal (10) and the test signal (18). Method according to one of the preceding claims,
wherein for the comparison of the first transfer function (T1) with the first reference function (R1) a cross-correlation is used. Method according to one of the preceding claims,
wherein the first reference function (R1) is determined from a measurement of the first transfer function (T1) under normalized conditions. Method according to one of claims 1 to 7,
wherein the first reference function (R1) is determined from temporally averaging a plurality of values of the first transfer function (T1) at different times. Method according to one of claims 2 to 9,
wherein the first transfer function (T1) is determined from a temporal averaging of a plurality of values of the transfer function of the open signal loop. Method according to one of the preceding claims,
wherein a defect of the first input transducer (4) and / or the output transducer (8) is detected. Method according to one of the preceding claims,
wherein a measure of a correlation between the first transfer function (T1) and the first reference function (R1) is determined, and
wherein the defect is detected by the degree of correlation. Method according to one of the preceding claims,
wherein a first polynomial is determined, which approximates the first transfer function (T1),
wherein a first reference polynomial is determined, which approximates the first reference function (R1), and
wherein the defect is detected by a coefficient comparison of the first polynomial and the first reference polynomial. Method according to one of the preceding claims,
wherein a second transfer function (T2) of a second acoustic system (28) comprising the output transducer (8) and a second input transducer (6) of the hearing instrument (1) is determined,
wherein at least one second reference function (R2) is determined for the second transfer function (T2),
wherein the second transfer function (T2) is compared with the second reference function (R2), and
wherein based on the comparison of the first transfer function (T1) with the first reference function (R1) and on the basis of the comparison of the second transfer function (T2) with the second reference function (R1) a defect in the hearing instrument (1) is detected. Method according to claim 11 in conjunction with claim 14,
wherein a first limit value (g1), a second limit value (g2) and a third limit value (g3) are specified,
wherein a first difference is formed from the first transfer function (T1) and the first reference function (R1),
wherein a second difference is formed from the second transfer function (T1) and the second reference function (R2),
wherein a third difference is formed from the first transfer function (T1) and the second transfer function (T2),
wherein a defect is detected at the first input transducer (4) when the first difference exceeds the first threshold (g1) in at least one frequency range without the second difference exceeding the second threshold (g2), and / or
wherein a defect in the output transducer (8) is detected, if in each case for the first difference and the second difference frequency ranges exist in which the first limit value (g1) or the second limit value (g2) is exceeded, without the third difference is the third (g3) exceeds limit. Hearing instrument (1) with at least one first input transducer (4) and an output transducer (8), which is set up to carry out the method according to one of the preceding claims. Hearing instrument (1) according to claim 16, which is designed as a hearing aid (2).

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