EP1290914A2 - Method for adjustment of a hearing aid to suit an individual - Google Patents

Abstract

The invention relates to a method for adjustment of a hearing aid to suit an individual. The method comprises, firstly, measuring the auditory sensitivity of the individual and quantifying the same by: (a) parameter(s) which may be weighted with a first factor. Further, a normal audio relationship, or the parameters thereof, are weighted with a second parameter and, finally, the weighted audio relationships, or the parameters thereof are used for determining the optimum hearing aid settings for the individual. According to the invention, the method has the advantage that a hearing aid can be significantly better adjusted to suit the individual.

Description

 Process for adapting a hearing aid to an individual

The present invention relates to a method for adapting a hearing aid to an individual.

Successful fitting of a hearing aid to an individual in whom hearing damage is present and is to be corrected is a decisive factor, among other things, the acceptance of the hearing aid.

Not only is the type and extent of hearing loss important, but also a number of other factors, such as personal, i.e. individual feeling of loudness.

A method for adapting a hearing aid to an individual is known from the laid-open specification of the European patent application with the number EP-A2-0 661 905. The known method relates to the correction of an individual, damaged psycho-acoustic perception by setting parameters in a hearing aid. The statistically determined average perception of people with normal hearing is used as the target function for the correction.

It is also known from the mentioned publication that a loudness scaling procedure is carried out in the hearing device to preset the dynamic compression. The degree of recruitment in the event of damage to the inner ear can thus be determined individually and individual compensation subsequently carried out. In addition, the publication by Kiessling, Kollmeier and Diller with the title "Care and Rehabilitation with Hearing Aids" (1997, Thieme, Stuttgart, New York) and Thomas Brand with the title "Analysis and optimization of psychophysical procedures in audiology" (Oldenburg: Library and Information System of the Univ., 2000. - 148 S Oldenburg, Diss., Univ., 1999. ISBN 3-8142-0721-1).

The standard loudness function used as the target function is determined on a collective of people with normal hearing, this standard loudness function being determined as far as possible using the same procedure as the actual individual measurement.

Various studies have shown that the variance of the norm loudness function is particularly large. An overview of the data found was published in an article by C. Elberling with the title "Loudness scaling revisited" (J Am Acad Audiol 10, pages 248 to 260, 1999).

The present invention is therefore based on the object of specifying a method in which settings are made on the hearing aid which enable improved adaptation of hearing aids to the loudness perception of the individual.

This object is achieved by the measures specified in claim 1. Advantageous embodiments of the invention are specified in further claims.

The invention has the following advantages: In that both the individual perception and the statistical norm perception of the hearing impaired in

Dependency of the hearing loss and the standard perception of normal hearing are taken into account when determining the settings of a hearing aid, and weighted according to data reliability, an optimal target function for the setting of the hearing aid is obtained for the individual, which also improves the hearing ability of the individual is. In other words, the invention has succeeded in obtaining an optimal target loudness, which takes into account the individual perception of loudness.

The invention is explained below with reference to drawings in more detail ^¬ play. It shows

Fig. 1 schematically, a quantification unit for

Quantification of an individually perceived loudness,

2 as a function of the sound level, the perceived loudness of the norm and of a hearing-impaired individual at a predetermined frequency,

Fig. 3 shows the slope of the loudness function as a function of hearing loss (HVLS function) for a hearing impaired individual and

Fig. 4 shows a level for the loudness = 0 as a function of

Hearing loss (HVLO function) for a hearing impaired individual.

As can already be seen from the introductory remarks, according to the invention, an individual and therefore better setting of hearing aids is made possible by taking into account both variations due to inaccurate measurements and variations due to different individual loudness sensations when adjusting the hearing aids, both the individually determined parameters and the standard loudness perception is weighted and contributes to determining the optimal adaptation. The term "optimal adaptation" here means in particular a balanced course for the compression to be set and the one to be set Gain, that is, the input / output behavior of a hearing aid as a function of frequency.

For compression, this is achieved in particular by representing the individual slopes of the individual scaling results as a function of the hearing loss and by an individual HVLS function, i.e. the slope of the loudness function as a function of the hearing loss HV can be approximated. A factor can be determined from the individual HVLS function in comparison to the hearing impaired standard HVLS function, which describes the loudness sensitivity of the individual in comparison to the norm.

For amplification, this is achieved by displaying the individual levels LO of the individual scaling results as a function of the hearing loss and by an individual HVLO function, i.e. the level for loudness = 0 as a function of hearing loss HV, can be approximated. From the individual HVLO function, compared to the

Hearing impaired standard HVLO function, an offset can be determined which describes the mean difference in the abscissa section of the loudness functions of the individual in comparison to the standard.

The individual method steps for adapting a hearing aid are explained below.

First, an audiogram is created. This is done by measuring the hearing thresholds for pure tones of different frequencies in a potential hearing device wearer. The measured increases in hearing thresholds are expressed and displayed as hearing loss in dB at each frequency or at certain frequency intervals. The audiogram can be used to determine in which hearing area there is a hearing loss. Furthermore Support points - ie individual frequencies - are determined on the basis of the audiogram, in which loudness scales are subsequently carried out in the manner described below.

The loudness "L" is a psycho-acoustic quantity, which indicates how "loud" an individual feels a presented acoustic signal.

In the case of natural acoustic signals, which are always broadband, the loudness does not match the physically transmitted energy of the signal. There is a psycho-acoustic evaluation of the incoming acoustic signal in individual frequency bands, the so-called critical bands. The loudness results from a band-specific signal processing and a cross-band overlay of the band-specific processing results, known under the term "loudness summation". These basics were described in detail by E. Zwicker, "Psychoacoustics", Springer-Verlag Berlin, University text, 1982.

However, it has been found that loudness is one of the most important psycho-acoustic variables that determine acoustic perception.

One possibility of capturing the individually perceived loudness on selected acoustic signals as a further usable variable is the one shown schematically in FIG. 1, for example from O. Heller, "Auditory field audiometry using the method of category division", Psychological Contributions 26, 1985 , or V. Hohmann, "Dynamic Compression for Hearing Aids, Psychoacoustic Fundamentals and Algorithms", dissertation UNI Göttingen, VDI-Verlag, series 17, No. 93, or Thomas Brand, Analysis and optimization of psychophysical procedures in audiology Oldenburg: Library and Information System of the Univ., 2000. - 148 S. Oldenburg, Diss. , Univ., 1999. ISBN 3-8142-0721-1, known method. In this case, an individual I is presented with an acoustic signal A, which is adjustable on a generator 1 with respect to the spectral composition and the transmitted sound pressure level. The individual I evaluates or "categorizes" the currently heard acoustic signal A according to e.g. B. eleven loudness levels or categories, as shown in Fig. 1. Numerical weights, for example from 0 to 10, are assigned to the levels.

With this procedure it is possible to measure the perceived individual loudness, i. H. to quantify. In the method according to the invention, this is carried out at at least one, preferably at three different frequencies or support points. This procedure is referred to below as loudness scaling.

In Fig. 2 the loudness L is recorded with a

Category scaling according to FIG. 1, plotted as a function of the mean sound pressure level in dB-SPL for a sinusoidal signal of frequency f _k . As can be seen from the course in FIG. 2, the loudness L _{M of} the standard increases non-linearly with the signal level in the selected representation, the slope course becomes in a first approximation for normal hearing people for all critical bands with the regression line entered as N in FIG. 2 reproduced with the slope α ,, in [categories per dB-SPL].

From this representation it is readily apparent that the model parameter α ,, corresponds to a non-linear amplification, approximately the same for normal hearing people in every critical frequency band, but for individuals with hearing _loss , with α _kI , to be described at every frequency or in every frequency band voices. Due to the straight line with the slope α _kI , the non-linear loudness function at the frequency f _k is approximated by a regression line.

In FIG. 2, L _kI typically denotes the course of the loudness L _{j of} a hearing _impaired person at a frequency f _k .

As can be seen from the comparison of the curves L _ω and L _kI , the curve of a hearing _impaired person has a larger offset (L ₀ ) to the zero point and is steeper than the curve of the norm. The larger offset corresponds to an increased hearing threshold, the phenomenon of the fundamentally steeper loudness curve is referred to as loudness recruitment and corresponds to an increased α parameter.

As has already been pointed out, such loudness scales are carried out at at least one, preferably at three support points - ie at one or more different frequencies. On the basis of these support points, a so-called HVLS function is determined by plotting the slopes of the loudness function α _{1 #} α ₂ , α ₃ , ... as a function of the hearing loss HV in dB.

FIG. 3 shows an HVLS function for a hearing-impaired individual, the individual HVLS function, dashed line, being determined by three support points using a suitable modeling described below.

It has been shown that the following model is particularly suitable for determining the gradient α as a function of the hearing loss HV (for hearing losses between 20dB and 100dB):

log ₁₀ (α) = a _a ^• HV + b _a ^■ log (HV) + VP _consta for 20dB <HV <lOOdB,

in which

α: slope of the loudness function,

HV: hearing loss in dB, a _a , b _a : constant function parameters and

VP _consta : individual function parameter that adapts the HVLS function to the support points α _{1 #} α ₂ , α ₃ , ...

is.

First, it should be noted at this point that the individual HVLS function shown in FIG. 3, due to its calculation from several support points, has less measurement-related scatter than the individual support points, and thus better reflects changes in individual perception. One could already get the target function for setting the hearing aid based on this individual HVSL function

Determine slope α at 0 dB hearing loss by extrapolation (dotted curve in Fig. 3) and adjust the hearing aid accordingly. It has been found that the hearing aid setting can be significantly improved if information about healthy hearing is also taken into account. It is proposed according to the invention that the standard loudness perception is used to determine the individually required compression with 0 dB hearing loss. According to the invention, the fact is taken into account that the loudness perception of people with normal hearing themselves has a non-negligible dispersion.

A preferred way to take into account the norm Loudness function consists in forming an average between the individual slope α determined by measurement and extrapolation at 0 dB hearing loss and the standard loudness slope, with a weighting corresponding to an expected spread of the values, both for the individual slope α at 0 dB hearing loss as well as with the standard loudness gradient. Weighting the individual scaling data as a function of both the quality of the individual scaling data and the number of measuring points for the individual scalings and the number of scalings carried out has proven to be advantageous. For individual scaling data of average quality in three frequencies, a weighting of the individual slope α at 0 dB hearing loss with a

Factor 2/3 and a weighting of the standard loudness gradient ot _u with a factor 1/3 an extremely good adaptation of the hearing aid can be achieved.

Analogous to the slope α of the loudness function, the

The abscissa sections L _{0 of} the loudness function in connection with the hearing loss determined in the audiogram derive an optimal band-specific amplification.

As has already been pointed out, loudness scales are carried out at at least one, preferably at three support points, ie at one or more different frequencies. On the basis of these reference points, the HVLO function is determined by plotting the abscissa sections of the loudness function L ₀₁ , L ₀₂ , L ₀₃ , ... as a function of the hearing loss HV in dB.

Figure 4 shows an HVLO function for a hearing impaired individual, using the individual HVLO function, dashed line, through three support points a suitable model formation, explained below, is determined.

It has been shown that the following model is particularly suitable for determining L ₀ as a function of hearing loss HV (for hearing losses between 20dB and 100dB):

L ₀ = a _L • HV + b _L ^■ log (HV) + VP _C

for 20dB <HV <l O OdB,

in which

L ₀ : level for loudness = 0, HV: hearing loss in dB, a _L , b _L : constant function _parameters and VP _constL : individual function parameters which send the HVLO function to the support points L ₀₁ , L ₀₂ , L ₀₃ , ... adjusts

First of all, it should be noted at this point that the HVLO function shown in FIG. 4, due to its calculation from several support points, has less measurement-related scatter than the individual support points, and thus better reflects changes in individual perception. The target function for setting the hearing aid could already be obtained based on this individual HVLO function, the level L ₀ at 0 dB hearing loss determined by extrapolation (dotted curve in FIG. 3) and the hearing aid set accordingly. It has been shown that the hearing aid setting can be significantly improved if, analogously to the gradient α Loudness function Information about healthy hearing is taken into account. It is proposed according to the invention that the standard loudness perception is used to determine the individually required compression with 0 dB hearing loss. According to the invention, the fact is taken into account that the loudness perception of people with normal hearing themselves has a non-negligible dispersion.

A preferred possibility for taking the standard loudness function into account is that a weighted mean value is formed between the individual level L ₀ determined by measurement and extrapolation at 0 dB hearing loss and the level Norm-L ₀ , with a weighting corresponding to an expected spread of the Values, both at the individual level L ₀ at 0 dB hearing loss and at the level Norm-L ₀ . Analogous to the slope of the loudness function, a weighting of the individual scaling data as a function of both the quality of the individual scaling data and the number of measuring points for the individual scalings and the number of scalings carried out has also proven advantageous for the level L ₀ .

For individual scaling data of average quality in three frequencies, an extremely good adjustment of the hearing aid can be achieved with a weighting of the individual level L ₀ at 0 dB hearing loss with a factor 1/3 and a weighting of the level Norm-L ₀ with a factor 2/3 ,

Claims

Claims: 1. Method for adapting a hearing aid to an individual taking into account individual perception of loudness, the method consisting in that the loudness perception of the individual is measured or quantified by parameters, this or these being weighted with a first factor, that a standard loudness perception or its parameters are weighted with a second factor and that the weighted loudness perception or its parameters are used for Setting the hearing aid can be used. 2. The method according to claim 1, characterized in that compression and / or amplification are set in the hearing aid, for this purpose the compression as a function of Frequency resp. the gain can be determined as a function of frequency. 3. The method according to claim 2, characterized in that to determine the compression, the loudness perception of the Individual is quantified using the HVLS function, which is determined by loudness scaling at at least one frequency. 4. The method according to claim 3, characterized in that the HVLS function by the formula log ₁₀ (α) = a _a • HV + b _a • log (HV) + VP _consta is modeled, whereby α: slope of the loudness function, - HV: hearing loss in dB, a _a , b _a : constant function _parameters and - VP _consta : individual function _parameter , which the Adapts HVLS function to the support points α _x , α ₂ , α ₃ , ... and that VP _{consta is determined} on the basis of at least one, preferably on the basis of three loudness _scales carried out at different frequencies. 5. The method according to claim 2, characterized in that to determine the gain, the loudness perception of the individual is quantified by means of the HVLO function, which is determined by loudness scaling at at least one frequency. 6. The method according to claim 5, characterized in that the HVLO function by the formula L ₀ = a _L ^• HV + b _L • log (HV) + VP _constL is modeled, whereby L ₀ : level for loudness = 0, HV: hearing loss in dB, a _L , b _L : constant function parameters and VP _constL : individual function parameter that adapts the HVLO function to the support points L ₀₁ , L ₀₂ , L ₀₃ , ... and that VP _{constL is determined} on the basis of at least one, preferably on the basis of three loudness _scales carried out at different frequencies. 7. The method according to one or more of claims 3 to 6, characterized in that the hearing loss is used to determine the frequencies in which loudness scales are carried out. 8. The method according to one or more of the preceding claims, characterized in that the size of the weighted factors depend on an assumed and / or determined accuracy of the loudness scaling data. 9. The method according to claim 8, characterized in that a value 2/3 is selected for the first factor and a value 1/3 for the second factor.