Method for fitting hearing aid gain and hearing aid fitting system

Abstract

A method for fitting a hearing aid gain (100) suitable for taking into account a vent effect. The invention also relates to a hearing aid fitting system suitable for carrying out said method.

Description

Technical Field

[0001] The present invention relates to a method of fitting a hearing aid system and a hearing aid fitting system adapted to perform said method. More particularly, the present invention relates to prescribing the gain of a hearing aid system by estimating a vent effect. Background Art

[0002] In the context of the present disclosure, a hearing aid may be understood as a small battery-powered microelectronic device designed to be worn by a hearing-impaired user behind or in the ear of a person. Prior to use, the hearing aid is adjusted by a hearing aid fitter according to a prescription. The prescription is based on a hearing test, generating a so-called audiogram, i.e. a representation of the independent hearing of the hearing-impaired user. The prescription is developed to achieve a setting in which the hearing aid will alleviate the hearing loss by amplifying sounds of frequencies in those parts of the audible frequency range in which the user suffers from a hearing defect. The hearing aid comprises one or more microphones, a battery, a microelectronic circuit and an acoustic output transducer, the microelectronic circuit comprising a signal processor suitable for providing amplification in those parts of the audible frequency range in which the user suffers from a hearing defect. The signal processor is preferably a digital signal processor. The hearing aid is encapsulated in a sleeve suitable for fitting behind or in the ear of a person.

[0003] In the present context, a hearing aid system may comprise a single hearing aid (a so-called monaural hearing aid system) or comprise two hearing aids, one for each ear of a hearing aid user (a so-called binaural hearing aid system). Furthermore, a hearing aid system may comprise an external device, such as a smartphone with a software application suitable for interacting with the other devices of the hearing aid system. Therefore, in the present context, the term "hearing aid system device" may denote either the hearing aid or the external device.

[0004] In general, a hearing aid system according to the invention is understood to mean any system which provides an output signal which can be perceived as an acoustic signal by a user or which contributes to the provision of such an output signal and which has means for compensating or contributing to compensating a personal hearing loss of a user. These systems may include hearing aids which may be worn on the body or on the head, in particular on or in the ear, and which may be fully or partially implanted. However, some devices whose primary purpose is not to compensate for hearing loss may still be considered as hearing aid systems, such as consumer electronic devices (televisions, hi-fi systems, mobile phones, MP3 players, etc.), as long as they have measures for compensating for personal hearing loss.

[0005] In WO 03 / 034784 A1 a digital hearing aid system is described wherein a part of the system is intended to deliver sound into the ear canal of a hearing aid user and this part provides the ear canal with a vent or ventilation channel to reduce the occurrence of the known occlusion effect which hearing aid users often find uncomfortable.

[0006] The geometry of the individual ear canal of the hearing aid user interacts with the dimensions of the ventilation duct and other mechanical properties of the hearing aid ear canal portion in determining the acoustic properties of the hearing aid and thus the actual gain of the hearing aid.

[0007] Even if a hearing aid has a sealed ear canal portion (which may also be indicated as earpiece in the following), leakage may occur between the ear canal wall and the ear canal portion of the hearing aid, which affects the acoustic properties of the hearing aid. Such leakage may even occur with hearing aids that use custom earpieces or have flexible earpieces, such as earpieces made of silicone that are generally adapted to the individual ear canal geometry of the user.

[0008] The fitting of hearing aids is usually done by an audiologist in a fitting session, during which the hearing threshold levels of the future hearing aid user in certain frequency bands are measured to determine the appropriate hearing aid gain in the frequency range. The frequency-dependent measurement of the hearing loss or so-called hearing threshold level (HTL) can be done by recording an audiogram. An audiogram is a graphical representation of a hearing test. It shows for each ear the minimum sound level required for the future hearing aid user to be able to hear sounds of each different frequency. The sounds provided in the test can be produced by a loudspeaker or a hearing aid-like device, which then also measures the sound pressure at the eardrum at the hearing threshold.

[0009] The necessary gain to be provided by the hearing aid is then calculated based on the audiogram and further fitting rules. However, if there are leaks or ventilation channels (vents) when using the actual hearing aid, this needs to be taken into account when determining the final hearing aid gain (which may be denoted as the vent effect in the following).

[0010] WO-A1-2007045271 discloses a method and system for fitting a hearing aid using estimated vent parameters, more specifically a method and system for fitting a hearing aid gain by estimating a best fit acoustic model of the hearing aid by modeling performed measurements using transmission line theory.

[0011] However, determining the vent effect is not a simple task, especially for so-called point-of-care earpieces (ie, flexible earpieces that are not personalized to a specific user) which may be difficult to model.

[0012] Therefore, there is a need for improved techniques for fitting hearing aid gain that take into account the acoustic characteristics of the hearing aid in a single ear canal of a hearing impaired person. Summary of the invention

[0013] It is therefore an object of the present invention to provide an improved method of fitting gain for a given type of hearing aid.

[0014] Therefore, in a first aspect, the present invention provides a method of fitting a hearing aid gain according to claim 1 .

[0015] This provides a method of fitting a hearing aid gain that is advantageous at least with respect to perceived sound quality and speech intelligibility.

[0016] In a second aspect, the present invention provides a hearing aid fitting system according to claim 9.

[0017] This provides a hearing aid fitting system gain which is advantageous with respect to providing a hearing aid fitting with at least improved perceived sound quality and speech intelligibility.

[0018] Further advantageous features emerge from the dependent claims.

[0019] Still other objects of the present invention will become apparent to those skilled in the art from the following description, in which the present invention will be explained in more detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be readily understood from the following detailed description taken in conjunction with the accompanying drawings. As will be appreciated, the present invention is capable of other different embodiments, and its several details are capable of modification in various obvious respects, all without departing from the present invention. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive. In the drawings:

[0021] Figure 1 A method for fitting a hearing aid gain according to an embodiment of the present invention is highly schematically illustrated;

[0022] Figure 2 A highly schematic illustration of the relationship between an acoustic feedback metric and a vent effect according to an embodiment of the present invention; and

[0023] Figure 3 Another relationship between an acoustic feedback metric and a vent effect according to an embodiment of the present invention is illustrated highly schematically. DETAILED DESCRIPTION

[0024] In the present context, the effect of a leak or vent in a hearing aid earpiece on the gain applied by the hearing aid may hereinafter be denoted as the vent effect.

[0025] The vent effect is defined as the sound pressure level at the eardrum provided by a hearing aid in a sealed ear canal (i.e., an ear canal with no intentional or unintentional acoustic leaks) relative to the sound pressure level provided by a hearing aid with an earpiece that does not provide a sealed ear canal. The vent effect can be expressed as gain values ​​for any number of frequency bands for a hearing aid.

[0026] Reference now Figure 1, which highly schematically illustrates a method 100 for fitting a hearing aid gain according to a first embodiment of the present invention.

[0027] In a first method step 101, sets of measurements of acoustic feedback metrics and vent effects based on insertion of a specific type of hearing aid into a plurality of real or artificial ears are provided.

[0028] According to an embodiment, the vent effect of a given type of hearing aid is measured by first inserting the hearing aid into a real ear or an artificial ear and measuring the sound pressure level at the ear drum. In the case of a real ear, the sound pressure level is typically measured using a thin probe that is adapted to have only a negligible effect on the measured vent effect. In the case of an artificial ear, the probe may be built into the artificial ear drum. Secondly, the real ear or artificial ear is acoustically sealed using, for example, some ear-print material (such as addition-cured silicone), and the resulting sound pressure level is measured. Finally, the vent effect of a given hearing aid type is determined as the difference between the two measured sound pressure levels.

[0029] According to an embodiment, the acoustic feedback measure is loop gain. In the present context, loop gain denotes an in-situ measurement of the sound transmitted through an acoustic system comprising a leakage path. The loop gain can be measured by a so-called feedback test, which is usually performed during a fitting procedure to estimate the maximum hearing aid gain. According to an embodiment, the method according to the invention will therefore advantageously not require any additional measurements during hearing aid fitting.

[0030] According to an embodiment, the specific type of hearing aid is defined by the shape and material of the hearing aid earpiece.

[0031] According to a more specific embodiment, the shape of the earpiece of the specific type of hearing aid is selected from a group of shapes including a single dome, a double dome, a tulip dome, a hollow sphere and a hollow bulb, wherein the latter two are further described in patent application WO-A1-2018 / 228988. Using more general terms, this type of earpiece can also be expressed as an instant fitting earpiece, which emphasizes the fact that these types of earpieces are not personalized to a specific user.

[0032] In a second method step 102, a relationship between an acoustic feedback measure and a ventilation effect in said particular type of hearing aid is determined using a plurality of sets of measured values.

[0033] To explain how this relationship can be determined, refer now to Figure 2 , which illustrates a portion of the relationship highly schematically in the form of a set of curves 200 in a coordinate system with a measured frequency-dependent acoustic feedback metric along the ordinate and a measured frequency-dependent vent effect along the abscissa.

[0034] Curves 201-a, 201-b, and 201-c each illustrate a function having a predefined shape suitable for obtaining measured acoustic feedback metric data points at a specific frequency or in a specific frequency band (not shown in the figure for clarity). Figure 2 The function of the predefined shape can capture the specific relationship between the acoustic feedback metric and the vent effect at a specific frequency. According to a more specific embodiment, the predefined function can be selected from predefined functions of linear functions with or without curvature and asymptotic exponents. The inventors have found that the predefined shape of the available function together with a controlled number of parameters is preferred to avoid overfitting to trends in the measured data points that are not relevant to determining the desired characteristics of a specific hearing aid type.

[0035] According to a preferred embodiment, the data points are measured at a frequency band corresponding to a hearing aid frequency band or at a center frequency of the respective hearing aid frequency band.

[0036] Therefore, according to the present embodiment, a set of predefined functions are then evaluated for each specific frequency or frequency band to determine the best function to model the measured data. This is done by evaluating the standard error and normality of the residuals, as these metrics are suitable for both linear and non-linear functions, allowing a direct comparison of the accuracy of the predictions and how well each function captures the potential acoustic feedback metric and vent effect relationship from the noisy measured data.

[0037] The best function to model the measured data is determined, namely Figure 2 , and then, depending on the implementation, each of the straight lines 202-a and 202-b can be used to find a specific frequency of the acoustic feedback metric and vent effect associated with the corresponding values ​​of the curves 201-a, 201-b and 201-c.

[0038] Reference now Figure 3 , which highly schematically illustrates the optimal function determined (given by Figure 2 ) can be combined across frequencies to form curves 301-a, 301-b and 301-c, each representing a measure of acoustic feedback as a function of frequency for a particular value of vent effect.

[0039] In a third method step 103, the acoustic feedback measure of the specific hearing aid to be fitted (when inserted in the ear of the user) is measured as a function of frequency. Figure 2 , the dot-dash curve 302 represents these measurement data.

[0040] In a fourth method step 104 , the vent effect of the specific hearing aid to be fitted is estimated based on the determined relationship between the acoustic feedback measure and the vent effect and the measured acoustic feedback measure of the specific hearing aid type to be fitted.

[0041] The estimation of the vent effect is performed using a method selected from the group consisting of least squares (such as least mean square), estimated minimum absolute residual and one-step sine estimation. Note that by using these methods to find the best possible fit between the measured acoustic feedback metric and one of the acoustic feedback metrics representing a particular value of the vent effect for the particular type of hearing aid to be fitted, it is ensured that even if the measured acoustic feedback metric is inaccurate at some frequencies, a reasonable estimate of the vent effect can still be found as long as a large number of the used frequencies or frequency bands contain accurate measured values.

[0042] According to a more specific embodiment, a plurality of rank correlation coefficients between the measured acoustic feedback metric and the measured vent effect are determined for each of the plurality of specific frequencies or frequency bands and based on the plurality of sets of measurements. Thus, the importance of the considered frequencies relative to each other can be determined based on the determined rank correlation coefficients and thus suitable weights are determined before calculating the error of one of the various least squares methods, such as, for example, the LMS error.

[0043] According to a more specific embodiment, the Spearman rank coefficient is used to determine the weight of each discrete frequency or frequency band by using multiple sets of measurements to find multiple measured vent effects at 350 Hz and corresponding multiple acoustic feedback metric values ​​measured at the frequencies considered. Note that, as already explained above, the multiple sets of measurements reflect the multiple different real ears and / or artificial ears that have been used to obtain the measurements.

[0044] In a fifth method step 105, a correction gain is determined based on the estimated vent effect. According to a specific embodiment, this can be done by increasing the gain to compensate for the loss of low frequency sound pressure level due to the vent effect.

[0045] According to another embodiment, the correction gain is adapted to reduce or eliminate the gain in low frequencies in order to avoid impairment of the sound quality due to interference between the directly transmitted sound and the sound processed by the hearing aid (the so-called comb filter effect).

[0046] In a sixth and final step 106 , the correction gain is incorporated into the gain of the hearing aid to be fitted, wherein the hearing aid to be fitted is of the specific type.

[0047] According to an alternative embodiment, the step of using the first plurality of sets of measurements to derive a relationship between the acoustic feedback equivalent and the vent effect comprises the step of training a neural network to determine the vent effect based on the measured frequency-dependent acoustic feedback metric.

[0048] According to yet another embodiment of the present invention, a hearing aid fitting system suitable for performing the various method embodiments presented above is disclosed.

[0049] According to a more specific embodiment, the hearing aid fitting system includes a display device adapted to display a plurality of hearing aid fitting procedure screens, which are adapted to initially prompt the hearing aid fitter to select a specific hearing aid earpiece; and secondly to provide a correction gain to be incorporated into the final hearing aid gain to compensate for the vent effect.

[0050] According to a more specific embodiment, the hearing aid fitting system is only adapted to use the various methods of the present invention when an instant fitting earpiece is selected.

[0051] According to additional embodiments, a hearing aid system capable of performing a feedback test and thus providing a measurement of an acoustic feedback metric according to the present invention may be configured to provide an adaptive correction gain to compensate for the sound loss due to the vent effect. This is particularly advantageous because the position and shape of the hearing aid earpiece in the ear (and the resulting vent effect) may change during the day, for example due to the user reinserting the earpiece into the ear, which may be done multiple times during the day, particularly for point-of-care fitting earpieces.

[0052] According to a more specific embodiment, the hearing aid system is operatively connected to a server, the server being configured to receive a measured acoustic feedback metric for a particular hearing aid type and to return a new correction gain in response thereto. According to a still more specific embodiment, the server is further configured to use the received measured acoustic feedback metric for various forms of data analysis, for example in order to investigate the reproducibility of positioning of a given type of earpiece for a given user, or in order to investigate whether a given type of earpiece appears to degrade over time. According to a still more specific embodiment, each time a fine adjustment is made in response to an automatic or user-initiated trigger, a measurement of the acoustic feedback metric is made and provided to the server, whereby it is possible to estimate to what extent the fine adjustment is a result of a changed vent effect, and more advantageously to give an indication of the correction gain that the user tends to prefer for a given measured acoustic feedback metric and therefore also for a given estimated vent effect, which knowledge can be used to update the recommended correction gain for a given measured acoustic feedback metric. Thus, the settings for a particular user can be improved based on data from other users.

[0053] According to a more specific embodiment, the step of determining the correction gain based on the estimated vent effect is based on an analysis of the relationship between the measured acoustic feedback metric and the currently applied correction gain at the point in time when the fine-tuning is performed in response to a user-initiated trigger, whereby an optimized value can be obtained at least with respect to general user preferences, since the desire for fine-tuning may be due to a correction gain value that is not preferred by a specific user.

[0054] According to another specific embodiment, the server is further configured to use the received measured acoustic feedback metrics to estimate how often a given hearing aid system user removes the hearing aid system or at least one hearing aid from the ear, and to use this data to obtain an optimized hearing aid setting at least with respect to general user preferences, since removing the hearing aid from the ear may be due to a lack of comfort or a less than optimal hearing aid setting when wearing the hearing aid.

[0055] Note that the present invention is particularly useful for determining the vent effect of point-of-care earpieces, as these types of earpieces are typically more flexible to be able to accommodate a variety of ear canals, resulting in performance that is strongly dependent on specific ear canal height variations, and their performance is therefore difficult to simulate.

[0056] Other modifications and variations in structure and procedure will be apparent to those skilled in the art.

Claims

1. A method for fitting hearing aid gain, comprising the following steps: - providing sets of measurements of acoustic feedback metrics and vent effects based on insertion of a particular type of hearing aid into at least one of a plurality of real ears and artificial ears; - determining a relationship between an acoustic feedback metric and a vent effect for said particular type of hearing aid using said plurality of sets of measurements; - measuring the acoustic feedback measure of the hearing aid to be fitted when inserted into the user's ear; - estimating a vent effect of the hearing aid to be fitted based on the determined relationship and the measured acoustic feedback measure; - determining a correction gain based on the estimated vent effect; and - Incorporating the correction gain into the gain of the hearing aid to be fitted, wherein the hearing aid to be fitted is of the specific type. 2 . The method for fitting a hearing aid gain according to claim 1 , wherein the specific type of hearing aid is defined at least by the shape and material of an earpiece of the hearing aid.

3. The method for fitting a hearing aid gain according to claim 2, wherein the shape of the earpiece of the specific type of hearing aid is selected from the group consisting of a dome shape, a double dome shape, a tulip dome shape, a hollow sphere shape, and a hollow bulb shape.

4. The method for fitting hearing aid gain according to claim 1, wherein the acoustic feedback metric and the vent effect are measured for a plurality of specific frequencies or frequency bands, and The step of using the plurality of sets of measurements to determine the relationship between the acoustic feedback metric and the vent effect comprises the following steps: - using a function with a predefined shape for each of the plurality of specific frequencies or frequency bands to obtain a linear or non-linear model of the relationship between the acoustic feedback measure and the vent effect; and - for said plurality of specific frequencies or frequency bands, combining each of said functions across frequencies to provide a plurality of relationships of said acoustic feedback measure as a function of frequency, wherein each of said relationships represents a specific vent effect.

5. The method for fitting hearing aid gain according to claim 4, further comprising the following steps: - determining a best possible fit between said measured acoustic feedback measure of the hearing aid to be fitted and a plurality of relationships of said acoustic feedback measure as a function of frequency.

6. The method for fitting a hearing aid gain according to claim 5, wherein the step of determining the best possible fit between the measured acoustic feedback metric of the hearing aid to be fitted and the plurality of relationships of the acoustic feedback metric as a function of frequency further comprises the following steps: - determining, for each of said plurality of specific frequencies or frequency bands and based on said plurality of sets of measured values, a plurality of rank correlation coefficients between the measured acoustic feedback metric and the measured vent effect; - Use the determined rank correlation coefficient to weight the importance of the considered frequencies relative to each other.

7. A method for fitting a hearing aid gain according to claim 5 or 6, wherein the step of determining the best possible fit between the measured acoustic feedback measure of the hearing aid to be fitted and the plurality of relationships of the acoustic feedback measure as a function of frequency is performed using a method selected from the group consisting of: least squares method, estimating the minimum absolute residual and one-step sine estimation.

8. A method of fitting a hearing aid gain according to claim 1, wherein the step of deriving the relationship between the acoustic feedback metric and the vent effect using the first plurality of sets of measurements comprises the further step of training a neural network to determine the vent effect based on the measured frequency-dependent acoustic feedback metric.

9. A hearing aid fitting system, configured to perform the method according to any one of claims 1-8.

10. The hearing aid fitting system according to claim 9, further comprising: - a display device suitable for: - Displays multiple hearing aid fitting process screens suitable for: - initially prompted the hearing aid dispenser to select a particular hearing aid earpiece; and - Secondly providing a correction gain to be incorporated into the final hearing aid gain to compensate for the vent effect.

11. A hearing aid system operatively connected to a server, the server being adapted to: - receiving measured acoustic feedback metrics from a plurality of hearing aid systems and specific types of said hearing aids, wherein said hearing aid systems are configured to provide adaptive correction gain to compensate for sound loss due to the vent effect, - using the received acoustic feedback metrics to optimize hearing aid system settings based on statistical analysis of said measured acoustic feedback metrics, - Providing optimized settings for said hearing aid system.

12. The hearing aid system according to claim 11, wherein the server is further adapted to: - Using said received measured acoustic feedback metric to estimate how long the hearing aid is removed from the ear, and using this knowledge to suggest an optimized hearing aid.

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