JP2014168200A - Hearing aid and muffled sound suppression device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hearing aid which can suppress muffled sound in the external auditory canal, discomfort for the user, without having any harmful effect on the hearing aid processing.SOLUTION: A hearing aid includes an external microphone 2, hearing aid processing means 20 generating a signal s(n) by performing hearing aid processing of an output signal from the external microphone 2, an earphone 4 for converting a signal u1(n)=s(n)-y(n) into a sound being outputted to a space in the external auditory canal, an ear microphone 5 for converting a sound transmitted through the external auditory canal into an electric signal, and signal processing means (21-26) including an adaptive filter 26 generating a signal y(n) by estimating the unnecessary components, other than the sound outputted from the earphone 4, based on a predetermined transfer function corresponding to the path from the input side of the earphone 4 to the output side of the ear microphone 5. The components of muffled sound d(n) is removed from the signal s(n), based on the signal y(n).

Description

  The present invention relates to a hearing aid and a booming sound suppression device having a configuration capable of suppressing the sound of noise that occurs in the ear canal.

  Since a general hearing aid used by a moderate to severe deaf person is worn with the ear canal sealed, there is a problem that a feeling of being uncomfortable for the hearing aid user occurs. That is, when a voice or mastication sound (hereinafter referred to as “buzzing sound”) that travels through the ear canal reaches the sealed ear canal, the volume of the sound increases unnaturally, giving the user a feeling of discomfort (a feeling of being full). Sometimes. As a measure to eliminate such a feeling of bulkiness, it is conceivable to use a structure in which a hearing aid is provided with a vent, or an open type hearing aid that does not seal the ear canal, but these methods use a loud sound output from the earphone to the microphone. There is a drawback that it is easy to return and inevitably howling occurs.

  Conventionally, there has been proposed a technique for removing unnecessary components from a desired signal by applying digital signal processing to an output signal of an in-ear microphone provided on the ear canal side of a hearing aid (Patent Document 1, 2). For example, Patent Document 1 collects sound of the external auditory canal with an in-ear microphone, and performs control so as to adapt the output signal of the digital signal processor (the signal after hearing aid processing) based on the output signal of the in-ear microphone. A hearing aid is disclosed. Further, for example, Patent Document 2 discloses a hearing aid that collects sound of the external auditory canal with an in-ear microphone and controls to feed back a low-frequency component of the output signal of the in-ear microphone to a signal to the earphone.

Special Table 2002-530034 US Pat. No. 7,477,754

  However, there are various inconveniences in order to realize a configuration for removing the unpleasant noise from the user by applying the techniques disclosed in Patent Documents 1 and 2. First, in the hearing aid disclosed in Patent Document 1, a process for removing unnecessary components such as a booming sound is integrated with a normal hearing aid process. In this case, the hearing aid processing in the hearing aid is a digital signal processing that appropriately adjusts the level and frequency characteristics of the audio signal according to the characteristics of the user's hearing and the usage environment. It is inevitable that the hearing aid process will be greatly affected, and there is a risk that the hearing aid will be inappropriately adjusted for the user. Further, the hearing aid disclosed in Patent Document 2 is not preferable in that the low frequency component of a normal sound signal necessary for the user is also suppressed when the low frequency component of the booming sound is suppressed. In addition, since the transfer function of the path from the earphone to the earphone via the space in the ear canal is not considered, it is difficult to obtain a sufficient effect of canceling the muffled sound. As described above, according to the conventional hearing aid, there is a problem that it is difficult to sufficiently suppress the unpleasant booming sound for the user without greatly affecting the hearing aid processing when the hearing aid is worn.

  The present invention has been made to solve these problems, and a hearing aid that can sufficiently suppress an unpleasant sound in the ear canal without adversely affecting the hearing aid processing when the hearing aid is worn. The purpose is to provide.

  In order to solve the above-mentioned problems, a hearing aid of the present invention is a hearing aid attached to the external auditory canal, and an external microphone (2) that converts external sound into an electrical signal, and an output signal of the external microphone (2) Hearing aid processing means (20) for generating a first signal (s (n)) by performing hearing aid processing, and a second signal (u1 (u1 ()) generated based on the first signal (s (n)) n)) which converts sound into sound and outputs it to the space in the ear canal, and an earphone provided to face the space in the ear canal and which converts sound transmitted through the ear canal into electrical signals ( 5) and sound input to the in-ear microphone (5) based on a predetermined transfer function corresponding to a path from the input side of the earphone (4) to the output side of the in-ear microphone (5) ( e (n)) from the earphone (4) Signal processing means (21-26) including an adaptive filter (26) for adaptively estimating an unnecessary component (d (n)) other than the sound to be generated and generating a third signal (y (n)); The second signal obtained by adding a component that cancels the unnecessary component (d (n)) to the first signal (s (n)) based on the third signal (y (n)) (U1 (n)) is generated.

  According to the hearing aid of the present invention, the sound output to the external auditory canal via the external microphone, the hearing aid processing means, and the earphone is added to an unnecessary component such as a booming sound in the space in the external auditory canal and input to the intraaural microphone. However, the unnecessary component can be canceled in the space in the ear canal based on the unnecessary component adaptively estimated by the feedback operation of the adaptive filter of the signal processing means. At this time, even if a signal having a phase opposite to that of the picking sound collected by the in-ear microphone is simply generated and fed back to the sound output from the earphone, the path from the earphone input side to the earphone output side However, according to the present invention, using the adaptive filter that is provided separately from the hearing aid processing means, the booming sound is transmitted through the path of the transfer function described above. By estimating the signal when propagating through, the muffled sound can be accurately canceled in the space inside the ear canal.

  In the hearing aid of the present invention, in addition to the adaptive filter, the signal processing means subtracts the third signal from the first signal and outputs the second signal; and A first estimation filter that inputs a second signal and outputs a fourth signal estimated based on the predetermined transfer function, and subtracts the fourth signal from the output signal of the in-ear microphone. A second subtractor that outputs a fifth signal that is an input signal of the adaptive filter; and a fifth signal that is input based on the predetermined transfer function and that outputs the sixth signal. A second estimation filter and a coefficient updating unit that adaptively updates the filter coefficient of the adaptive filter based on the output signal of the in-ear microphone and the sixth signal are configured. With this configuration, the first estimation filter and the second subtracter are used to input the fifth signal including only the booming noise component to the adaptive filter, and the second estimation filter and the coefficient updating unit are used. Thus, the filter coefficient of the adaptive filter can be adaptively updated, and finally a component that cancels the muffled sound can be added to the signal of the necessary sound by using the first subtracter.

  In the hearing aid of the present invention, the coefficient updating unit may be configured to update a filter coefficient of the adaptive filter according to an LMS (Least Mean Square) algorithm. The basis of the LMS algorithm is the steepest descent method, and the filter coefficient is updated so as to minimize the mean square of the error, and the convergence speed can be improved with a simple configuration.

  In the hearing aid of the present invention, the first estimation filter and the second estimation filter include a transfer function R (z) representing the characteristics of the earphone, and an output side of the earphone to an input side of the in-ear microphone. Using the transfer function F (z) and the transfer function M (z) representing the characteristics of the in-ear microphone, P (z) = R (z) · F (z) · M (z). It is configured to have a transfer function P (z). In this case, R (z) and M (z) constituting the transfer function P (z) can be accurately determined based on the characteristics of the earphone and the earbud microphone, and F (z) related to the propagation of sound in the ear canal. A well-known method for determining the value is known.

  In order to solve the above-mentioned problem, the booming noise suppression device of the present invention is a booming noise suppression device having a housing attached to the ear canal, wherein the input signal is a first signal, and the first signal is the first signal. An earphone that converts the second signal generated based on this signal into sound and outputs the sound to a space in the ear canal, and a sound that is provided facing the space in the ear canal and that transmits the sound transmitted through the ear canal to an electrical signal. Based on the in-ear microphone to be converted and at least a transfer function corresponding to a path from the input side of the earphone to the output side of the in-ear microphone, it is output from the earphone among sounds input to the in-ear microphone. Signal processing means including an adaptive filter that adaptively estimates unnecessary components other than sound to generate a third signal, and removes the unnecessary components from the first signal based on the third signal It is characterized in that to generate the second signal. Thus, the present invention is not limited to hearing aids, and can be applied to various devices that are worn on the user's external auditory canal, and can sufficiently suppress the unpleasant noise that is uncomfortable for the user when these devices are worn. .

  As described above, according to the present invention, when a hearing aid or the like is attached and the external auditory canal is substantially sealed, the user feels a sense of being overwhelmed (discomfort) due to the noise generated in the external ear canal. Can be prevented. In this case, since the processing for canceling the muffled sound is executed by the signal processing means including the adaptive filter separately from the hearing aid processing, the hearing aid processing does not hinder the adjustment of the hearing aid. In addition, the transfer function of the path from the earphone through the ear canal to the in-ear microphone can be appropriately considered to cancel the muffled sound, thus improving the effect of canceling the muffled sound and improving the quality of the hearing aid. Can be realized.

It is a block diagram which shows the schematic structure of the hearing aid of this embodiment. In the hearing aid of this embodiment, it is a block diagram which shows the specific structural example relevant to digital signal processing. It is a figure which shows the example of a structure of a general filtered-x LMS. FIG. 4 is a conceptual diagram when the configuration of the present embodiment is simplified and applied to the filtered-x LMS configuration of FIG. 3. It is a figure explaining the effect of the hearing aid to which this invention is applied, Comprising: It is a figure which shows the example of the time waveform of the time waveform of the input sound pressure, and the simulation signal of a booming sound. FIG. 5 shows a comparison of the time waveform of the sound pressure in the ear canal for the case where the configuration of the present embodiment is not employed and the case where the configuration of the present embodiment is employed, using the simulated sound of the booming sound of FIG. FIG. It is a figure which shows the structural example of the hearing aid which concerns on a 1st modification. It is a figure which shows the structural example of the hearing aid which concerns on a 2nd modification.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example in which the present invention is applied to a hearing aid attached to a user's ear canal.

  FIG. 1 is a block diagram showing a schematic configuration of a hearing aid according to the present embodiment. As shown in FIG. 1, the hearing aid of this embodiment includes an external microphone 2, a DSP (Digital Signal Processor) 3, and an earphone 4 in a case 1 as a housing having a shape that can be inserted into a user's ear. And an in-ear microphone 5, a battery holder 6, and a button battery 7 inside the battery holder 6. The case 1 includes a face plate 1 a facing the external space of the ear and a shell 1 b disposed along the external auditory canal 10. An external microphone 2 is attached to the face plate 1a via a sound port, and an earphone 4 and an in-ear microphone 5 are provided in a portion of the shell 1b facing the space S between the eardrum 11 and the ear canal 10. Each is attached via a sound outlet. Although not shown in FIG. 1, the shell 1 b of the case 1 may be provided with a vent that communicates the outside with the ear canal 10. In this case, the role of the vent is to exhaust the moisture of the external auditory canal 10 to the outside, and also has an effect of suppressing the muffled sound. If this is insufficient, the effect of applying the present invention can be expected.

  In the configuration of FIG. 1, the external microphone 2 collects sound transmitted from the external space and converts it into an electrical signal. On the other hand, the in-ear microphone 5 collects sound transmitted from the space S in the ear canal 10 and converts it into an electric signal. The earphone 4 adjacent to the in-ear microphone 5 converts an electrical signal into sound and outputs the sound to the space S. The earphone 4 and the in-ear microphone 5 located on the space S side in the external ear canal 10 are members indispensable for the process of canceling the muffled sound in the external ear canal 10. That is, when the hearing aid user's own voice or mastication sound is transmitted to the external auditory canal 10, if the opening is closed by the case 1, these sounds will be heard loudly (buzzing sound), and the user will feel uncomfortable. There is a risk of giving a feeling of being full. As a countermeasure for this, in the present embodiment, the process of canceling the booming sound is executed in the hearing aid, and the details will be described later.

  The DSP 3 performs digital signal processing including the above-described processing for canceling the booming sound on the electrical signal input from the external microphone 2 and the in-ear microphone 5 and the electrical signal output to the earphone 4. Specific processing will be described later. A button battery 7 held inside the battery holder 6 supplies power to each component of the hearing aid. The button battery 7 can be replaced by opening and closing the opening of the battery holder 6 as necessary.

  Next, FIG. 2 is a block diagram showing a specific configuration example related to digital signal processing in the hearing aid of the present embodiment. As shown in FIG. 2, the functional elements of the DSP 3 include a hearing aid processing unit 20, two subtractors 21 and 22, two estimation filters 23 and 24, a coefficient update unit 25, and an adaptive filter 26. . Among these, the functional elements other than the hearing aid processing unit 20 function as the signal processing means of the present invention in an integrated manner. 2 shows the external microphone 2, the earphone 4, and the in-ear microphone 5 of FIG. 1, and the sound that reaches the in-ear microphone 5 from the earphone 4 in the space S in the ear canal 10, Each transmission path is shown.

  First, the output signal of the external microphone 2 is input to the hearing aid processing unit 20. The hearing aid processing unit 20 is a hearing aid processing unit that performs predetermined hearing aid processing that is individually set in conformity with each user on the output signal of the external microphone 2, and generates a signal s (n). The hearing aid processing performed by the hearing aid processing unit 20 includes, for example, the hearing characteristics and usage environment of the hearing aid user, such as multiband compression, noise reduction, tone control, volume control, and output restriction processing for the output signal of the external microphone 2. It is possible to apply various processes according to the above. Although omitted in FIG. 2, an AD converter for converting an analog signal into a digital signal is provided on the output side of the external microphone 2 and the in-ear microphone 5, and a digital signal is provided on the input side of the earphone 4. It is necessary to provide a DA converter that converts a signal into an analog signal.

  The signal s (n) output from the hearing aid processing unit 20 is input to the subtractor 21 (the first subtracter of the present invention). The subtractor 21 generates a signal u1 (n) obtained by subtracting the output signal y (n) of the adaptive filter 26 from the signal s (n). In this case, the signal u1 (n) is expressed by the following equation (1).

u1 (n) = s (n) -y (n) (1)
The adaptive filter 26 is a filter that adaptively generates an output signal y (n) for canceling the muffled sound, and details thereof will be described later. The signal u1 (n) output from the subtractor 21 is input to each of the earphone 4 and the estimation filter 23. As described with reference to FIG. 1, the sound output from the earphone 4 propagates through the space S in the ear canal 10 to reach the eardrum 11 and is also input to the in-ear microphone 5. At this time, the muffled sound that has reached the space S is input to the in-ear microphone 5 through a route different from the sound output from the earphone 4.

  Here, the transfer function of the earphone 4 is R (z), the transfer function of the path from the output side of the earphone 4 to the input side of the in-ear microphone 5 is F (z), and the transfer function of the in-ear microphone 5 is M (z). ) Respectively. In this case, the above-described signal u1 (n) is converted into the output sound u2 (n) via the transfer function R (z) and the transfer function F (z). When the output sound u2 (n) from the earphone 4 and the booming sound d (n) are added by the virtual adder 12, the resultant sound e (n) is input to the in-ear microphone 5. Can think. In this case, the synthesized sound e (n) is expressed by the following equation (2).

e (n) = u2 (n) + d (n) (2)
The above synthesized sound e (n) is converted into a signal e ′ (n) via the transfer function M (z) of the in-ear microphone 5 and then input to each of the subtractor 22 and the coefficient updating unit 25. The On the other hand, the above-described estimation filter 23 (the first estimation filter of the present invention) is an estimation signal u1 ′ (n ). Therefore, the transfer function P (z) of the estimation filter 23 is expressed by the following equation (3) using the above-described transfer functions R (z), F (z), and M (z).

P (z) = R (z) F (z) M (z) (3)
The estimation signal u1 ′ (n) output from the estimation filter 23 is input to the subtractor 22. The subtracter 22 (the second subtracter of the present invention) subtracts the estimated signal u1 ′ (n) from the above-described signal e ′ (n) output from the in-ear microphone 5 and inputs the signal to the adaptive filter 26. A signal x (n) is generated. In this case, the input signal x (n) is expressed by the following equation (4).

x (n) = e ′ (n) −u1 ′ (n) (4)
On the other hand, the input signal x (n) is input to the estimation filter 24 in addition to the adaptive filter 26. This estimation filter 24 (second estimation filter of the present invention) uses an estimation signal x ′ (n) when it is assumed that the input signal x (n) has propagated along the path from the earphone 4 through the in-ear microphone 5. This is a filter to be generated. The estimation filter 23 has the same transfer function P (z) as equation (3).

  In this way, the two estimation filters 23 and 24 have the same transfer function P (z) = R (z) F (z) M (z). On the other hand, the estimation signal x ′ (n) output from the estimation filter 24 is input to the coefficient updating unit 25. The coefficient updating unit 25 adaptively updates the filter coefficient used for the calculation of the adaptive filter 26 according to an LMS (Least Mean Square) algorithm. That is, the coefficient updating unit 25 receives the signal e ′ (n) and the estimated signal x ′ (n) described above, and calculates filter coefficients that minimize the mean square of the signal e ′ (n). .

  The adaptive filter 26 performs a filter operation based on the transfer function C (z) on the input signal x (n) based on the filter coefficient determined by the coefficient update unit 25 to generate an output signal y (n). . At this time, due to the operations of the estimation filter 23 and the subtracter 22, the input signal x (n) is a signal obtained by estimating the muffled sound. Therefore, the output signal y (n) of the adaptive filter 26 is transferred from the earphone 4 to the in-ear microphone 5 by the estimation filter 24, the coefficient updating unit 25, and the adaptive filter 26, and the transfer function R (z), The signal includes a booming sound in a state where the influence of F (z) is considered. As the adaptive filter 26, for example, FIR (Finite Impulse Response) having a predetermined number of taps (for example, 32 taps) can be used.

  As described above, by subtracting the output signal y (n) of the adaptive filter 26 from the signal s (n) output from the hearing aid processing unit 20, the influence of the transfer function is reflected and the component of the booming sound is reduced. The signal u1 (n) to which the signal that is effectively canceled is added can be generated, and can be output as a sound from the earphone 4. Therefore, the user wearing the hearing aid can hear a comfortable sound in which the muffled sound is sufficiently suppressed in the ear canal 10. In this case, as can be seen from FIG. 2, since the whole signal processing means necessary for canceling the muffled sound is arranged in the DSP 3 after the hearing aid processing unit 20, the hearing aid processing of the hearing aid processing unit 20 is adversely affected. The noise can be canceled without giving a sound.

  Here, the adaptive filter 26 in FIG. 2 and its periphery have a so-called filtered-x LMS configuration. FIG. 3 shows an example of a general filtered-x LMS configuration. That is, in FIG. 3, an adaptive filter 30 that inputs an input signal x (n) and outputs an output signal y (n), and an error signal e () obtained by subtracting the output signal y (n) from the signal d (n). In addition to the LMS coefficient updating unit 31 for obtaining the updated value ΔWn of the filter coefficient Wn so as to minimize the root mean square of n), a filter 32 is provided before the LMS coefficient updating unit 31 to which the input signal x (n) is input. Has been inserted.

  On the other hand, FIG. 4 is a conceptual diagram when the configuration of the present embodiment (FIG. 2) is simplified and applied to the filtered-x LMS configuration of FIG. In FIG. 4, a basic signal path in which the components in FIG. 2 are omitted is assumed, and the transfer function M (z) of the in-ear microphone 5 is also ignored. In FIG. 4, the adaptive filter 26 and the coefficient updating unit 25 correspond to the adaptive filter 30 and the LMS coefficient updating unit 31 in FIG. 3, respectively. The filter 32 having the transfer function A (z) is provided in the same manner as in the configuration of FIG. 3, but in addition, has a transfer function A (z) inserted into the output signal y (n). 3 is different from FIG. 3 in that a filter 33 is provided. This filter 33 corresponds to the path from the earphone 4 to the adder 12 in FIG. 2 and assumes that the output signal of the filter 33 is synthesized with a muffled sound. The transfer functions A (z) of the filters 32 and 33 can be expressed as A (z) = R (z) F (z).

  Generally, it is known that when a filter is inserted on the output side of the adaptive filter 26, the adaptive filter 26 does not operate properly. However, considering the system linearity in the configuration of FIG. 4, the positions of the adaptive filter 26 and the filter 33 can be interchanged. Further, in the path after the input signal x (n) branches, the configuration in which the two filters 32 and 33 are inserted in parallel is one having a transfer function A (z) in consideration of the linearity of the system. Is inserted before the branch of the input signal x (n), and the path is branched to the adaptive filter 26 and the coefficient update unit 25 at a position after that. Therefore, in the configuration of the present embodiment, it can be considered that the appropriate operation of the adaptive filter 26 is guaranteed by the estimation filter 24.

On the other hand, FIG. 4 does not consider the in-ear microphone 5 shown in FIG. 2, but actually, the transfer function M (z) of the in-ear microphone 5 is put in the path of the error signal e (n) in FIG. An inserted configuration is assumed. In this case, for the normal operation of the adaptive filter 26, the path from the input signal x (n) to the coefficient updating unit 25 via the adaptive filter 26 and the filter 33, and the filter 32 from the input signal x (n). It is assumed that the relative phase lag between the path reaching the coefficient updating unit 25 via the lag is only the phase lag due to the adaptive filter 26. Here, when the phase lag of each of the two filters 32 and 33 having the transfer function A (z) is τ _A and the phase lag of the transfer function M (z) is τ _M , adaptation of the former path is performed. The phase delay excluding the phase delay due to the filter 26 is τ _A + τ _M , and the phase delay of the latter path is τ _A. Therefore, in order to eliminate the phase delay, the transfer function of the filter 32 may be A (z) M (z) = R (z) F (z) M (z), and the estimation filter 24 corresponding to the filter 32 may be used. (FIG. 2) shows that this relationship is satisfied. However, when the in-ear microphone 5 has a flat frequency characteristic, the phase delay does not become a problem, so the transfer function of the estimation filter 24 may be set to A (z).

  Next, the effect of the hearing aid to which the present invention is applied will be described with reference to FIGS. In FIGS. 5 and 6, a simulation was performed on the configuration example of FIG. 2 under predetermined conditions, and the effect of actually suppressing the booming noise was confirmed. First, FIG. 5A shows an example of a time waveform of sound pressure input to the external microphone 2, and FIG. 5B is applied to the external auditory canal 10 based on the audio signal of FIG. A time waveform of a signal generated by simulating a booming sound d (n) is shown. For example, by applying a low-pass filter to a recorded predetermined audio signal, a simulated signal of the booming sound d (n) shown in FIG. 5B can be generated. On the other hand, FIG. 6A shows the inside of the external auditory canal 10 in the case where the configuration of the present embodiment is not used by using the simulated signal of the booming sound d (n) of FIG. 5B for comparison with the present embodiment. The time waveform of the sound pressure in is shown. 6B shows the sound pressure time in the external auditory canal 10 when the configuration of the present embodiment (FIG. 2) is employed using the simulated signal of the booming sound d (n) of FIG. 5B. The waveform is shown. As is apparent from a comparison between FIGS. 6A and 6B, it can be seen that the volume of the booming sound d (n) can be sufficiently suppressed by employing the configuration of the present embodiment.

  As mentioned above, although the hearing aid of this embodiment was demonstrated using FIGS. 1-6, the application object of this invention is not restricted to a hearing aid. That is, the present invention can be applied to various devices including a housing that is mounted on the ear canal and a structure that outputs sound from the earphone to the ear canal. For example, the present invention can be applied to an earphone device for audio. For example, in FIG. 2, without providing the hearing aid processing unit 20, an input means for inputting an acoustic signal output from the audio device is provided, and the signal output from the input means is represented by the signal s (n) in FIG. As described above, the present invention can be applied. Further, by providing an inverting amplifier for inverting the output signal y (n) of the adaptive filter 26 without providing this input means, and using the output as the signal u1 (n) in FIG. The present invention can be applied to earplugs having In addition, the present invention can be applied as a booming noise suppression device to various devices that can be attached to the ear canal.

  Furthermore, the present invention is not limited to the above-described embodiment, and there are various modifications. For example, FIG. 7 shows a configuration example of a hearing aid according to the first modification. As shown in FIG. 7, the first modification is provided with a transfer function setting unit 27 for setting the transfer functions P (z) of the respective estimation filters 23 and 24 in the configuration of FIG. According to the first modification, the transfer function setting unit 27 is appropriately set according to the shape and size of the user's ear canal 10 and the eardrum 11, and the desired transfer function P (z ). On the other hand, FIG. 8 shows a configuration example of a hearing aid according to the second modification. As shown in FIG. 8, in the second modification, the estimation filter 23 is replaced with an adaptive filter 23a and a coefficient update unit 28 associated with the adaptive filter 23a is provided in the configuration of FIG. The transfer function P (z) obtained by the adaptive filter 23 a is copied to the estimation filter 24. The functions of the adaptive filter 23a and the coefficient update unit 28 are as described using the adaptive filter 26 and the coefficient update unit 25 in FIG. According to the second modification, the accuracy of the transfer function P (z) used in the adaptive filter 23a and the estimation filter 24 can be improved, and the effect of canceling the muffled sound can be improved. Even if the transfer function F (z) changes, the performance can be improved. Can keep.

  As mentioned above, although the content of this invention was concretely demonstrated based on this embodiment, this invention is not limited to each above-mentioned embodiment, A various change can be given in the range which does not deviate from the summary. . For example, in FIG. 2, the configuration of the rear stage of the hearing aid processing unit 20 includes an adaptive filter 26 and considers a transfer function corresponding to the path from the input side of the earphone 4 to the output side of the in-ear microphone 5. Based on the above, it is possible to employ various configurations for removing unnecessary components including a booming sound.

1 ... Case 2 ... External microphone 3 ... DSP
4 ... Earphone 5 ... In-ear microphone 6 ... Battery holder 7 ... Button battery 10 ... External ear canal 11 ... Tympanic membrane 12 ... Adder 20 ... Hearing aid processing unit 21, 22 ... Subtractor 23, 24 ... Estimation filter 25, 28 ... Coefficient updating unit 26, 23a ... adaptive filter 27 ... transfer function setting unit

Claims (6)

A hearing aid worn in the ear canal,
An external microphone that converts external sound into an electrical signal;
Hearing aid processing means for generating a first signal by performing hearing aid processing on the output signal of the external microphone;
An earphone that converts a second signal generated based on the first signal into sound and outputs the sound to a space in the ear canal;
An in-ear microphone that is provided facing the space in the ear canal and converts sound in the space in the ear canal into an electrical signal;
Based on a predetermined transfer function corresponding to a path from the input side of the earphone to the output side of the in-ear microphone, unnecessary components other than the sound output from the earphone out of the sound input to the in-ear microphone are included. Signal processing means including an adaptive filter for adaptively estimating and generating a third signal;
And generating the second signal obtained by adding a component that cancels out the unnecessary component to the first signal based on the third signal. The signal processing means, in addition to the adaptive filter,
A first subtractor that subtracts the third signal from the first signal and outputs the second signal;
A first estimation filter that inputs the second signal and outputs a fourth signal estimated based on the predetermined transfer function;
A second subtracter that subtracts the fourth signal from the output signal of the in-ear microphone and outputs a fifth signal that is an input signal of the adaptive filter;
A second estimation filter that inputs the fifth signal and outputs a sixth signal estimated based on the predetermined transfer function;
A coefficient updating unit for updating a filter coefficient of the adaptive filter based on the output signal of the in-ear microphone and the sixth signal;
The hearing aid according to claim 1, comprising:   The hearing aid according to claim 2, wherein the coefficient updating unit updates a filter coefficient of the adaptive filter according to an LMS (Least Mean Square) algorithm. The first estimation filter and the second estimation filter include a transfer function R (z) representing the characteristics of the earphone, and a transfer function F (z) from the output side of the earphone to the input side of the in-ear microphone. And a transfer function M (z) representing the characteristics of the in-ear microphone,
P (z) = R (z) · F (z) · M (z)
The hearing aid according to claim 2, wherein the hearing aid has a transfer function P (z) expressed as follows. A booming sound suppressing device having a housing attached to the ear canal,
Input means for inputting a signal from the outside and outputting it as a first signal;
An earphone that converts a second signal generated based on the first signal into sound and outputs the sound to a space in the ear canal;
An in-ear microphone that is provided facing the space in the ear canal and converts sound in the space in the ear canal into an electrical signal;
Based on at least a transfer function corresponding to a path from the input side of the earphone to the output side of the in-ear microphone, unnecessary components other than the sound output from the earphone out of the sound input to the in-ear microphone are included. Signal processing means including an adaptive filter for adaptively estimating and generating a third signal;
And generating the second signal to which the component for canceling the unnecessary component is added from the first signal based on the third signal. A booming sound suppressing device having a housing attached to the ear canal,
Earphones that output sound to the space inside the ear canal,
An in-ear microphone that is provided facing the space in the ear canal and converts sound in the space in the ear canal into an electrical signal;
Based on the transfer function corresponding to the path from the input side of the earphone to the output side of the in-ear microphone, unnecessary components other than the sound output from the earphone out of the sound input to the in-ear microphone are estimated. Signal processing means including an adaptive filter for generating unnecessary component signals,
Inverting means for inverting the unnecessary component signal;
And a humming noise suppression device, wherein the output of the inverting means is input to the earphone.