TWI623234B - Hearing aid and automatic multi-frequency filter gain control method thereof - Google Patents

Abstract

The present invention provides a hearing aid comprising: an audio input stage for receiving an input audio signal and converting the input audio signal into an input digital signal; an audio processing circuit for performing an input electrical signal An automatic frequency division filter gain control method for generating an output digital signal; and an audio output stage for converting the output digital signal into an output audio signal for playing, wherein the automatic frequency division filtering gain control method comprises: obtaining a hearing attenuation curve of a user; calculating a plurality of adapted frequency gains corresponding to the hearing attenuation curve; applying a segmented bandpass filter to an input audio signal, wherein the segmented bandpass filter is included for different frequency bands a plurality of band pass filters; calculating an adapted frequency relationship matrix corresponding to the segmented band pass filter; calculating one of each band pass filter according to the plurality of adapted frequency gains and the adapted frequency relationship matrix Gain.

Description

Hearing aid and its automatic frequency division filtering gain control method

The present invention relates to hearing aids, and more particularly to a hearing aid and its automatic frequency division filtering gain control method.

Wide dynamic range compression (WDRC) technology is widely used in the range of hearing aids. After a long period of research, it is found that the startup time is about 5ms to meet the user's needs, but the recovery time varies with the environment. Figure 1 is a schematic diagram showing the hearing compensation curve for wide dynamic range compression to convert the input audio signal. Curve 110 (the dotted line portion) refers to the conversion curve of the unprocessed input audio signal, that is, the input audio signal is equal to the output audio signal. The curve 120 (solid line part) refers to a conversion curve of the input audio signal subjected to wide dynamic range compression, and can be divided into four areas 131~134 according to the strength of the input audio signal. The intensity of the audio signal can usually be expressed in terms of dB SPL (sound pressure level). Region 131 refers to a high linear region (eg, greater than 90 dB SPL), meaning that the saturated sound pressure of a hearing impaired person is the same as that of a normal person, without amplification. Region 132 refers to a compression zone (eg, between 55 and 90 dB SPL) to adjust the dynamic range of the user's listening domain. Area 133 means low linearity The (low linear) zone (for example, between 40 and 55 db SPL) is used to help the hearing impaired to amplify the faint voice. Region 134 refers to an expansion region (e.g., less than 40 dB SPL) in which the intensity of the audio signal is rather weak, and the input audio signal may be less loud than the speech sound signal, without too much amplification. In addition, there is a volume limiter at the output of the hearing aid to limit the maximum volume of the output audio signal, for example, limited to 110dB SPL.

In general, when hearing-impaired people wear hearing aids, they will compensate for the different frequencies of hearing-impaired hearing impairment curves. Since the frequencies of the input sound signals have different gains, if the picture of the input audio signal is divided into different numbers of bands, the range of each band is relatively small, for example, the input audio signal can be converted by Fourier transform. Switching from the time domain to the frequency domain, the corresponding gain can be adjusted for individual frequencies, but the computational complexity of the Fourier transform is relatively large, which can cause the audio processing circuitry in the hearing aid to be quite Big burden.

Therefore, there is a need for a hearing aid and its automatic frequency division filtering gain control method to solve the above problems.

The present invention provides a hearing aid comprising: an audio input stage for receiving an input audio signal and converting the input audio signal into an input digital signal; an audio processing circuit for performing an input electrical signal An automatic frequency division filter gain control method for generating an output digital signal; and an audio output stage for converting the output digital signal into an output audio signal for playing, wherein the automatic frequency division filtering gain control method comprises: obtaining One use One of the hearing attenuation curves; calculating a plurality of adapted frequency gains corresponding to the hearing attenuation curve; applying a segmented bandpass filter to an input audio signal, wherein the segmented bandpass filter includes a plurality of complex bands a band pass filter; calculating an adapted frequency relationship matrix corresponding to the segmented band pass filter; calculating a gain of each band pass filter according to the plurality of adapted frequency gains and the adapted frequency relationship matrix.

The present invention further provides an automatic frequency division filtering gain control method for a hearing aid, wherein the hearing aid comprises an audio input stage, an audio processing circuit, and an audio output stage, the method comprising: receiving an input by the audio input stage An audio signal, and converting the input audio signal into an input digital signal; using the audio processing circuit to perform an automatic frequency division filtering gain control method on the input electrical signal to generate an output digital signal; and using the audio output stage The output digital signal is converted into an output audio signal and played, wherein the automatic frequency division filtering gain control method comprises: obtaining a hearing attenuation curve of a user; and calculating a plurality of adaptive frequency gains corresponding to the hearing attenuation curve; Applying a segmented bandpass filter to an input audio signal, wherein the segmented bandpass filter includes a plurality of bandpass filters for different frequency bands; calculating an adapted frequency corresponding to the segmented bandpass filter a relationship matrix; calculating each band according to the plurality of adapted frequency gains and the adapted frequency relationship matrix One filter gain.

110, 120‧‧‧ Curve

131-134‧‧‧Area

200‧‧‧ hearing aids

210‧‧‧Optical input stage

211‧‧‧ microphone

212‧‧‧ Analog Digital Converter

220‧‧‧Operation Processing Circuit

230‧‧‧ audio output stage

231‧‧‧ Receiver

232‧‧‧Digital Analog Converter

10‧‧‧ Input audio signal

11‧‧‧ Input electrical signal

12‧‧‧Input digital signal

14‧‧‧Output digital signal

15‧‧‧ Output electrical signal

16‧‧‧ Output audio signal

311-314, 411-414‧‧‧ Curve

510-550‧‧‧

Figure 1 is a schematic diagram showing the hearing compensation curve for wide dynamic range compression to convert the input audio signal.

Figure 2 is a block diagram showing a hearing aid in accordance with an embodiment of the present invention.

Figures 3A and 3B show schematic diagrams of the distribution of different bandpass filters.

4A and 4B are diagrams showing the distribution of different band pass filters in accordance with an embodiment of the present invention.

Figure 5 is a flow chart showing an automatic frequency division filter gain control method in accordance with an embodiment of the present invention.

Figure 6 is a diagram showing the hearing attenuation curve and the adaptation gain curve in accordance with an embodiment of the present invention.

The above described objects, features and advantages of the present invention will become more apparent from the description of the appended claims.

Figure 2 is a block diagram showing a hearing aid in accordance with an embodiment of the present invention. In one embodiment, the hearing aid 200 includes an audio input stage 210, an audio processing circuit 220, and an audio output stage 230. The audio input stage 210 includes a microphone 211 and an analog-to-digital converter (ADC) 212. The microphone 211 is configured to receive an input audio signal 10 (for example, an analog audio signal), and convert the input audio signal 10 into an input electrical signal 11, and the analog digital converter 112 is configured to input the electrical signal 11 The input is converted to an input digital signal 12 as an input to the audio processing circuit 220.

The audio processing circuit 220 performs an automatic frequency division filtering gain control method and/or a wide dynamic range compression process on the input digital signal 12 to generate an output digital signal 14. The details of the automatic crossover filter gain control method will be Details are given later. It should be understood that the above wide dynamic range compression processing includes a predetermined wide dynamic range compression conversion curve, which is performed on various hearing and frequency hearing measurements in advance for each user's hearing characteristics, thereby obtaining individual widths. Dynamic range compression conversion curve. In addition, when the sound intensity of the input audio signal changes, the audio processing circuit 220 also adjusts the recovery time of the hearing aid 200, thereby providing a better user experience for the hearing impaired. In some embodiments, the audio processing circuit 220 can be a microcontroller, a processor, a digital signal processor (DSP), or an application-oriented integrated circuit (ASIC), but the present invention is not Limited to this.

Furthermore, when performing wide dynamic range compression, the audio processing circuit 220 refers to the recovery time factor associated with the input audio signal to adjust the delay (ie, recovery time) of the output audio signal. The audio output stage 230 includes, for example, a receiver 231 (or speaker) and a digital analog converter 232. The digital analog converter 232 is operative to convert the output digital signal 14 produced by the audio processing circuit 220 into an output electrical signal 15. The receiver 231 can convert the output electrical signal 15 into an output audio signal 16 (eg, an analog audio signal) and play it for the user to listen to the output audio signal 16. For convenience of explanation, in the following embodiments, the conversion between the audio signal and the electrical signal is omitted, and only the input audio signal and the output audio signal are used for explanation.

Figures 3A and 3B show schematic diagrams of the distribution of different bandpass filters. For example, when using a bandpass filter in the time domain, a corresponding bandpass filter is set for different frequency band ranges, such as the bandpass filter 310 for the low frequency band in FIG. 3A and for high Bandpass filter 311 of the band, and bandpass filter 312 for the low band and bandpass filter for the high band in Fig. 3B 313 is shown. However, the intermediate frequency of each band must maintain the same gain. However, when there is gain at high frequencies, its discontinuity in the boundary between different frequency bands is more serious.

4A and 4B are diagrams showing the distribution of different band pass filters in accordance with an embodiment of the present invention. In an embodiment, the present invention combines bandpass filters with larger filtering bands, which can have different gains at different frequencies, and the transitions in different boundary regions are relatively continuous, as shown in FIG. 4A. The band pass filter 410 for the low band and the band pass filter 411 for the high band, and the band pass filter 412 for the low band and the band pass filter 413 for the high band in Fig. 4B are shown. . It is to be noted that, for convenience of explanation, two bands are taken as an example in FIGS. 4A and 4B, and in the following-described embodiments, four bands are taken as an example for description. Compared to the bandpass filters in Figures 3A and 3B, the bandpass filters in Figures 4A and 4B have a flat slope on both sides of the band.

Figure 5 is a flow chart showing an automatic frequency division filter gain control method in accordance with an embodiment of the present invention. At block 510, a hearing attenuation curve for one of the users is obtained. For example, the present invention measures the hearing detection of a user (ie, a hearing impaired person) using four sets of adapted frequencies f ₁ to f ₄ , such as f ₁ =500 Hz , f ₂ =1000 Hz , f ₃ = 2000 Hz , f ₄ = 4000 Hz , to confirm the hearing attenuation curve of the hearing impaired.

At block 520, an adaptive frequency gain process is performed. For example, different hearing gain curves can be used for different hearing gain methods (half gain method, 1/3 gain method, POGOII method, Berger method, NAL-R method, etc.) to obtain relative Gain values G ₅₀₀ , G ₁₀₀₀ , G ₂₀₀₀ , G ₄₀₀₀ at the test frequency. A comparison of the hearing attenuation curve and the adaptation gain curve can be referred to Fig. 6, wherein the hearing attenuation curve is curve 610 and the adaptation gain curve is curve 620. It should be noted that the hearing attenuation curve and the adaptation gain curve will vary depending on the hearing impaired person in use. In an embodiment, the NAL-R method is used in the present invention to calculate the gain value of the hearing decline curve at different test frequencies, but the invention is not limited thereto.

At block 530, a segmented bandpass filter is applied. For example, the invention may use a conventional finite impulse response (finite impulse response, FIR) band-pass filter b _c (k). The kth coefficient of this finite impulse response bandpass filter b _c (k) is matched with the appropriate window w(k) . That segment comprises a band pass filter of band-pass filters of different frequency bands, each frequency band, for example band-pass filter _{B c (k) = b c} (k). w(k) , wherein the first frequency band B1 is 0 to 1000 Hz, the second frequency band B2 is 1000 to 2000 Hz, the third frequency band B3 is 2000 to 4000 Hz, and the fourth frequency band B4 is 4000 to 6000 Hz.

At block 540, a band pass filter calculation B _c (k) of the matrix corresponding to the adaptation frequency relationship. For example, the present invention designs a sine wave signal S _fj ( k ) of an adaptation frequency using a sampling frequency f _s , and the sine wave signal S _fj ( k ) can be expressed as follows:

The sine wave signal S _fj ( k ) passes through a band pass filter of each frequency band, and calculates an adaptive frequency relationship matrix. For example, in the above steps, a band pass filter of four frequency bands and four adaptive frequency gains are used, so The adapted frequency relationship matrix is a 4x4 matrix in this embodiment. For example, the adaptation frequency relationship matrix can be expressed as follows:

In brief, although the bandpass filter B _c (k) of each band is calculated by the window w(k) , in reality, each bandpass filter has a boundary with other bandpass filters on both sides. Therefore, it is necessary to calculate the mutual influence, that is, the above-mentioned adaptation frequency relationship matrix.

At block 550, calculated for each band-pass filter B _c (k) of the gain. For example, the conversion adaptation frequency gain can be represented by the following matrix:

In simple terms, the segmented bandpass filter is represented by B _c (k) , and the adaptive frequency relationship matrix is Said that the adaptation frequency gain is Indicates that the gain required for each bandpass filter is And the relationship of the above parameters is:

At this time, the gain required for each band pass filter B _c (k) can be expressed by the following equation:

The adapted frequency gain has been calculated in blocks 520 and 540, respectively. And adaptive frequency relationship matrix Therefore, the gain required for each bandpass filter B _c (k) Can be based on known adaptation frequency gain And adaptive frequency relationship matrix Calculated, for example, will adapt the frequency relationship matrix Multiplying the inverse matrix by the adaptive frequency gain To obtain the gain required for each bandpass filter B _c (k) .

The present invention has been disclosed in the above preferred embodiments, and is not intended to limit the scope of the present invention. Any one of ordinary skill in the art can make a few changes without departing from the spirit and scope of the invention. The scope of protection of the present invention is therefore defined by the scope of the appended claims.

Claims (8)

A hearing aid comprises: an audio input stage for receiving an input audio signal and converting the input audio signal into an input digital signal; an audio processing circuit for performing an automatic frequency division filtering gain on the input digital signal Controlling the method to generate an output digital signal; and an audio output stage for converting and outputting the output digital signal to an output audio signal, wherein the automatic frequency division filtering gain control method comprises: acquiring one of the users a hearing attenuation curve; calculating a plurality of adapted frequency gains corresponding to the hearing attenuation curve; applying a segmented bandpass filter to an input audio signal, wherein the segmented bandpass filter includes a plurality of bandpasses for different frequency bands a filter; calculating an adapted frequency relationship matrix corresponding to the segmented bandpass filter; and multiplying an inverse matrix of the adapted frequency relationship matrix by the plurality of adapted frequency gains to obtain respective bandpass filters One gain is needed. The hearing aid of claim 1, wherein the plurality of adapted frequency gain systems correspond to 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz, respectively. The hearing aid of claim 1, wherein the segmented bandpass filter is a finite impulse response bandpass filter. The hearing aid of claim 1, wherein the audio processing circuit calculates the segment by using the sine wave signal having a predetermined sampling frequency to pass the plurality of band pass filters of the segmented band pass filter. Bandpass filter Corresponding to this adaptation frequency relationship matrix. An automatic frequency division filtering gain control method for a hearing aid, wherein the hearing aid comprises an audio input stage, an audio processing circuit, and an audio output stage, the method comprising: receiving an input audio signal by using the audio input stage, and Converting the input audio signal into an input digital signal; performing an automatic frequency division filtering gain control method on the input digital signal by the audio processing circuit to generate an output digital signal; and converting the output digital signal into An audio signal is output and played, wherein the automatic frequency division filter gain control method comprises: obtaining a hearing attenuation curve of a user; calculating a plurality of adapted frequency gains corresponding to the hearing attenuation curve; applying an input audio signal a segmented bandpass filter, wherein the segmented bandpass filter includes a plurality of bandpass filters for different frequency bands; calculating an adapted frequency relationship matrix corresponding to the segmented bandpass filter; An inverse frequency matrix of one of the adaptive frequency relationship matrices is multiplied by the plurality of adapted frequency gains to obtain each One pass filter gain required. The automatic frequency division filter gain control method according to claim 5, wherein the plurality of adapted frequency gain systems correspond to 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz, respectively. The automatic frequency division filtering gain control method according to claim 5, wherein the segmented band pass filter is a finite impulse response band pass filter. The automatic frequency division filter gain control method according to claim 5, further comprising: calculating, by using the sine wave signal having a predetermined sampling frequency, the plurality of band pass filters of the segmented band pass filter, thereby calculating The adapted frequency relationship matrix corresponding to the segmented bandpass filter.