KR102063824B1 - Apparatus and Method for Cancelling Acoustic Feedback in Hearing Aids - Google Patents

Abstract

The present invention relates to an apparatus and method for removing acoustic feedback for a hearing aid, and the apparatus for removing acoustic feedback for a hearing aid according to the present invention includes: an analyzer configured to generate digital data of multiple bands with respect to a signal input through a microphone; A feedback canceller for detecting a frequency band for generating acoustic feedback from digital data and adjusting a gain for the multiband digital data such that the value of the frequency band for generating acoustic feedback is attenuated, and a gain-adjusted multiband for And a synthesizer for synthesizing an acoustic signal to be output from the digital data to the receiver.

Description

Apparatus and Method for Canceling Acoustic Feedback in Hearing Aids}

TECHNICAL FIELD The present invention relates to a feedback cancellation apparatus and method, and more particularly, to an acoustic feedback cancellation apparatus and method for a multi-band hearing aid.

Acoustic feedback is acoustic interference between an acoustic generator, such as a speaker, and an acoustic sensing device, such as a microphone, producing unwanted noise sounds and reducing the maximum gain available in a hearing aid. Accordingly, since acoustic feedback causes inconvenience to the wearer of the hearing aid, the removal of the acoustic feedback is very important in the design and manufacture of the hearing aid.

Conventional discontinuous systems that stop hearing aid signal processing when acoustic feedback is detected, estimate the feedback path using a probe signal, such as white noise, and adjust the coefficients of the adaptive filter using the estimated feedback path. However, such a conventional discontinuous system has a problem that the signal-to-noise ratio is reduced by the probe signal so that it can be used only for severe hearing loss which is not affected by noise.

Conventional continuous systems that compensate for the shortcomings of discontinuous systems are implemented using the least mean square (LMS) and afine projection (AP) series algorithms, and the feedback path is adjusted by adjusting the coefficients of the adaptive filter based on the input signal. Estimate. However, the conventional continuous system has the advantage of not damaging the original speech because only the feedback component is estimated and removed, but high gain is required because the order of the filter is limited when the performance of the signal processor is insufficient. However, there is a problem that is difficult to use in the case of high hearing loss. In addition, in the conventional continuous system, since the feedback path is estimated based on the frequency component having the largest power, there is a problem in that an estimation error for a frequency component having a relatively small power becomes large. There is a problem that the path estimation for the entire frequency band is not effective because the gain has a great influence on the feedback generation.

In Hearing Aid System of Patent No. 10-1231866 (announced Feb. 8, 2013), feedback is detected based on the average size of the spectrum of the current and past frequency bands. Based on this, acoustic feedback is detected and removed using a notch filter method. However, such a system does not reflect the fact that acoustic feedback can occur well in a specific frequency band, which is not effective. In addition, since feedback is detected by reflecting only a change in amplitude for each frequency band without considering the overall characteristics of the currently input sound, erroneous detection may be performed, which may cause problems in speech recognition.

Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a low complexity because the adaptive notch filter in the frequency domain is used as compared to the conventional adaptive filter method, and has low complexity. Compared to the prior art that requires the present invention to provide a sound feedback removing apparatus and method of the multi-band hearing aid using only the currently input sound data reflecting the characteristics of the feedback that can be well generated in a specific frequency band.

First, to summarize the features of the present invention, the acoustic feedback cancellation apparatus according to an aspect of the present invention for achieving the above object, the analysis unit for generating digital data of the multi-band for the signal input through the microphone; A feedback canceller for detecting a frequency band for generating acoustic feedback from the multiband digital data and adjusting a gain for the multiband digital data such that a value of the frequency band for generating the acoustic feedback is attenuated; And a synthesizer for synthesizing an acoustic signal to be output to a receiver from the multi-band digital data whose gain is adjusted.

The feedback canceller processes in real time the multi-band digital data for a signal currently input through the microphone without the use of an adaptive filter and without using historical data.

The feedback canceller may include: an energy average calculator configured to calculate an energy average of data for a band below a predetermined frequency of the multiple bands; A maximum energy band searching unit searching for a maximum energy band among bands greater than the predetermined frequency among the multiple bands; A ratio calculator for calculating a ratio between the energy of the maximum energy band and the energy average; And a gain adjuster that adjusts a gain for the digital data of the multi-band so that the value of the frequency band generating the acoustic feedback is attenuated according to the ratio.

The gain adjusting unit applies attenuation gain to the data of the maximum energy band among the digital data of the multi-band.

The gain adjusting unit may further apply attenuation gain to a peripheral band of a predetermined range with respect to the maximum energy band.

The acoustic feedback removing device is characterized in that for hearing aids.

In addition, the acoustic feedback removing method according to another aspect of the present invention, generating a multi-band digital data for the signal input through the microphone; Detecting a frequency band for generating acoustic feedback from the multiband digital data and adjusting a gain for the multiband digital data such that a value of the frequency band for generating the acoustic feedback is attenuated; And synthesizing an acoustic signal to be output to a receiver from the multi-band digital data whose gain is adjusted.

In the step of adjusting the gain, real time processing of the multi-band digital data for a signal currently input through the microphone without the use of an adaptive filter and without the use of past data.

Adjusting the gain may include calculating an energy average of data for a band below a predetermined frequency of the multiple bands; Searching for a maximum energy band of bands greater than the predetermined frequency of the multiple bands; Calculating a ratio between the energy of the maximum energy band and the energy average; And adjusting the gain for the multi-band digital data such that the value of the frequency band generating the acoustic feedback is attenuated according to the ratio.

In the adjusting of the gain, attenuation gain is applied to the data of the maximum energy band among the multiband digital data.

If necessary, the attenuation gain may be further applied to the peripheral band in a predetermined range with respect to the maximum energy band.

According to the apparatus and method for removing acoustic feedback for a multi-band hearing aid according to the present invention, the adaptive notch filter in the frequency domain is used as compared with the conventional adaptive filter method, and thus it is possible to stably remove the acoustic feedback with low complexity. have.

In addition, when used in conjunction with the method of removing feedback using an adaptive filter in the frequency domain, a second method can protect the user of the hearing aid in situations where the conventional method cannot reliably make feedback path estimation or in the case of false estimation or divergence. Can be used as a step safety device.

And, compared to the conventional method of detecting feedback by using the average size of the spectrum of each frequency band of the present and past frame, by using only the acoustic data currently input reflecting the characteristics of the feedback that can be well generated in a specific frequency band By doing so, you can benefit from memory usage and computation.

1 is a view for explaining the acoustic feedback removing device for a hearing aid according to an embodiment of the present invention.
2 is a flowchart illustrating an operation of an acoustic feedback removing device for hearing aids according to an embodiment of the present invention.
3A and 3B are examples of impulse response waveforms of acoustic feedback applied to hearing aids.
4A and 4B show amplitude response waveforms for FIGS. 3A and 3B, respectively.
FIG. 5 is a waveform diagram illustrating a receiver output sound source according to whether or not the acoustic feedback removing device of the present invention is applied when the acoustic feedback of FIGS. 3A and 3B is applied to the hearing aid.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the present invention. In this case, the same components in each drawing are represented by the same reference numerals as much as possible. In addition, detailed descriptions of already known functions and / or configurations are omitted. The following description focuses on parts necessary for understanding the operation according to various embodiments, and descriptions of elements that may obscure the gist of the description are omitted. In addition, some components of the drawings may be exaggerated, omitted, or schematically illustrated. The size of each component does not entirely reflect the actual size, and thus the contents described herein are not limited by the relative size or spacing of the components drawn in the respective drawings.

1 is a view for explaining the acoustic feedback removing device 200 for hearing aids according to an embodiment of the present invention.

Referring to FIG. 1, an acoustic feedback removing apparatus 200 for a hearing aid according to an embodiment of the present invention includes an analyzer 210, a feedback remover 220, and a synthesizer 230.

The analyzer 210 generates multi-band digital data Band_1, .., Band_N (N is a natural number of two or more) with respect to the signal input through the microphone 211.

To this end, the analyzer 210 may include a microphone 211 for generating an analog electrical signal corresponding to a voice and an A / D (Analog / Digital) converter for converting the output of the microphone 211 into digital data. 212), an input buffer 213 that sequentially stores and outputs the A / D converter 212, a window application unit 214 that selects valid data from an output of the input buffer 213, and a window application unit 214. An FFT processing unit 215 generates the multi-band digital data Band_1, .., Band_N by processing the output by FFT (Fast Fourier Transform).

The feedback remover 220 detects a frequency band for generating acoustic feedback from the multi-band digital data Band_1, .., Band_N output from the analyzer 210, and a value of the frequency band for generating the corresponding acoustic feedback is attenuated. The gain for the multiband digital data Band_1, .., Band_N is adjusted as much as possible.

To this end, the feedback remover 220, the energy average calculation unit 221 for calculating the energy average of the data for a band (eg band_m or less band) less than a predetermined frequency (for example, f1) of the multi-band, the Maximum energy band search unit 222 that searches for the maximum energy band (eg, Band_k) among the bands larger than the predetermined frequency (eg, f1) among multiple bands, and energy and energy average of the maximum energy band (eg, Band_k). A ratio calculation unit 223 for calculating a ratio between the energy averages from the calculation unit 221, and a value of a frequency band for generating the acoustic feedback according to the ratio calculated by the ratio calculation unit 223 is attenuated. The maximum energy band (eg Band_k) of the multiband digital data (.Band_k, .., Band_N) larger than the frequency (eg f1) and its peripheral band (..Band_k-2, Band_k, if desired) in a predetermined range. -1, Band_k, Band_k + 1, ..) gain for the data It includes a gain control unit 224 to adjust.

As such, the feedback canceller 220 processes the multi-band digital data Band_1, .., Band_N for the signal currently input through the microphone 211 without using an adaptive filter and using historical data. .

The synthesizer 230 synthesizes an acoustic signal to be output from the multi-band digital data whose gain is adjusted by the gain adjuster 224 to the receiver 235 which is an audio output device.

To this end, the synthesis unit 230, the IFFT processing unit 231, IFFT processing unit for converting the multi-band digital data whose gain is adjusted by the gain control unit 224 to the time-axis data by processing the IFFT (Inverse Fast Fourier Transform) A window application unit 232 for selecting valid data from the output of the output of 231, an output buffer 233 for sequentially storing and outputting the output of the window application unit 232, and converting an output of the output buffer 233 into an analog signal A digital / analog (D / A) converter 234 and a receiver 235 for outputting sound according to the output signal of the D / A converter 234.

Hereinafter, an operation of the acoustic feedback removing apparatus 200 for hearing aids according to an embodiment of the present invention will be described in more detail with reference to the flowchart of FIG. 2.

2 is a flowchart illustrating an operation of the acoustic feedback removing device 200 for hearing aids according to an embodiment of the present invention.

In the present invention, first, as shown in the flowchart of FIG. 2, the A / D converter 212, the input buffer 213, and the window application unit 214 with respect to the signal inputted by the analyzer 210 through the microphone 211. ), Through the sequential processing in the FFT processor 215, multiband digital data Band_1, .., Band_N divided into respective frequency bands are generated (S110).

When the analyzer 210 outputs the multi-band digital data Band_1, .., Band_N, the feedback canceller 220 generates a frequency band for generating acoustic feedback from the multi-band digital data Band_1, .., Band_N. To adjust the gain of the multi-band digital data Band_k, .., Band_N larger than a predetermined frequency (for example, f1) so as to attenuate the frequency band for generating the corresponding acoustic feedback (S120).

That is, the energy average calculation unit 221 calculates an energy average of data for a band (eg, Band_m or less) of a predetermined frequency (eg, f1) or less among the multiple bands, and the maximum energy band search unit 222 The maximum energy band (eg, Band_k) is searched among the bands larger than the predetermined frequency (eg, f1) among the multiple bands, and the ratio calculator 223 calculates the energy and energy average of the maximum energy band (eg, Band_k). The ratio between the energy averages from the unit 221 is calculated. Through such a ratio between the energy of the maximum energy band (eg, Band_k) and the energy average, it is possible to detect whether feedback occurs and the corresponding frequency band, and based on this, feedback can be suppressed by adjusting the gain of each frequency band. To this end, the gain adjusting unit 224 may be configured to reduce the value of the frequency band for generating the acoustic feedback according to the ratio calculated by the ratio calculating unit 223. Adjust the gain for data in the maximum energy band (e.g., Band_k) and, if necessary, its peripheral bands (..Band_k-2, Band_k-1, Band_k, Band_k + 1, ...).

For example, the gain control unit 224 calculates attenuation gains based on the ratio between the energy of the maximum energy band (eg, Band_k) and the energy average (eg, B), but uses digital data of multiple bands (Band_k, The same gain for the data of the maximum energy band (e.g. Band_k) among the .., Band_N and its peripheral band (..Band_k-2, Band_k-1, Band_k, Band_k + 1, ..) in a predetermined range, if necessary. May be applied, or a gain according to a difference with a frequency of a maximum energy band (eg, Band_k) (eg, a gain determined to decrease attenuation as the frequency difference increases) may be applied. For example, if the energy of Band_k is much larger than the average energy of Band_1 ~ Band_m, the gain of Band_k is 0.1, the gain of Band_k + 1, Band_k-1, .. etc is 0.5, Band_k + 2, Band_k-2, .. The gain of 0.7 can be removed to eliminate the feedback. Here, the number of gain values is shown as an example and may be variously determined according to a design specification.

Next, based on this ratio between the energy of the maximum energy band (eg, Band_k) and the energy average as above, the feedback canceller 220 adjusts the gain such that the value of the frequency band that generates the acoustic feedback is attenuated. The synthesizer 230 synthesizes an acoustic signal to be output to the receiver 235 which is an audio output device from the multi-band digital data whose gain is adjusted by the gain adjuster 224 (S130). That is, the synthesis unit 230 sequentially processes the IFFT processing unit 231, the window application unit 232, the output buffer 233, and the D / A converter 234 with respect to the multi-band digital data whose gain is adjusted. Through this, an acoustic signal is output to the receiver 235.

3A and 3B are examples of impulse response waveforms of acoustic feedback applied to hearing aids. 4A and 4B show amplitude response waveforms for FIGS. 3A and 3B, respectively. 5 is a waveform diagram illustrating a receiver output sound source according to whether or not the acoustic feedback removing device of the present invention is applied when the acoustic feedback of FIGS. 3A and 3B is applied to the hearing aid.

A 16 kHz mono sound source was used for the experiment, assuming that the hearing aid's forward path gain 20 dB, mean band 0-1250 Hz, and maximum search band 1250-8000 Hz.

Acoustic feedback with a response waveform as shown in FIGS. 3A and 4A is applied between 4 seconds and 8 seconds as shown in FIG. 5, and acoustic feedback with a response waveform as shown in FIGS. 3B and 4B is shown. When applied between 12 to 16 seconds as shown in 5, it was confirmed that the acoustic feedback is removed using the acoustic feedback removing device 200 of the present invention, such as 510, 520. However, as shown in 511 and 521, when the acoustic feedback removing apparatus 200 of the present invention was not applied, the acoustic feedback was not removed and the signal output to the receiver was saturated.

As described above, the hearing aid acoustic feedback removing device 200 according to an embodiment of the present invention uses an adaptive notch filter form in the frequency domain as compared with the conventional adaptive filter method, and thus has a low complexity and is stable. Acoustic feedback can be eliminated. In addition, when used in conjunction with the method of removing feedback using an adaptive filter in the frequency domain, a second method can protect the user of the hearing aid in situations where the conventional method cannot reliably make feedback path estimation or in the case of false estimation or divergence. Can be used as a step safety device. And, compared to the conventional method of detecting feedback by using the average size of the spectrum of each frequency band of the present and past frame, by using only the acoustic data currently input reflecting the characteristics of the feedback that can be well generated in a specific frequency band By doing so, you can benefit from memory usage and computation.

In the present invention as described above has been described by the specific embodiments, such as specific components and limited embodiments and drawings, but this is provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations may be made without departing from the essential features of the present invention. Accordingly, the spirit of the present invention should not be limited to the described embodiments, and all technical ideas having equivalent or equivalent modifications to the claims as well as the following claims are included in the scope of the present invention. It should be interpreted as.

Analysis unit 210
Feedback Eliminator (220)
Synthesis unit 230
Energy average calculation part 221
Maximum Energy Band Seeker (222)
Rate calculation part (223)
Gain adjuster 224

Claims (15)

An analyzer configured to generate digital data of multiple bands with respect to a signal input through a microphone;
A feedback canceller for detecting a frequency band for generating acoustic feedback from the multiband digital data and adjusting a gain for the multiband digital data such that a value of the frequency band for generating the acoustic feedback is attenuated; And
A synthesizer for synthesizing an acoustic signal to be output to a receiver from the multi-band digital data whose gain is adjusted;
The feedback remover,
An energy average calculator configured to calculate an energy average of data for a band below a predetermined frequency of the multiple bands;
A maximum energy band searching unit searching for a maximum energy band among bands greater than the predetermined frequency among the multiple bands;
A ratio calculator for calculating a ratio between the energy of the maximum energy band and the energy average; And
Detecting a frequency band for generating acoustic feedback according to the ratio, and adjusting a gain for the digital data of the multi-band so that the value of the frequency band for generating the acoustic feedback is attenuated. And a gain adjuster. The method of claim 1,
And the feedback canceller is configured to process the multi-band digital data in real time with a notch filter method in a frequency domain, on a signal currently input through the microphone. delete The method of claim 1,
The gain control unit,
And attenuation gain is applied to the data of the maximum energy band among the multiband digital data. The method of claim 4, wherein
The gain control unit,
And applying attenuation gains to the periphery band in a predetermined range relative to the maximum energy band. The method of claim 1,
And the acoustic feedback removing device is for a hearing aid. Generating multi-band digital data with respect to a signal input through a microphone;
Detecting a frequency band for generating acoustic feedback from the multiband digital data and adjusting a gain for the multiband digital data such that a value of the frequency band for generating the acoustic feedback is attenuated; And
Synthesizing an acoustic signal to be output to a receiver from the multi-band digital data whose gain is adjusted;
Adjusting the gain,
Calculating an energy average of data for a band below a predetermined frequency of the multiple bands;
Searching for a maximum energy band of bands greater than the predetermined frequency of the multiple bands;
Calculating a ratio between the energy of the maximum energy band and the energy average; And
Detecting a frequency band for generating acoustic feedback according to the ratio, and adjusting a gain for the multi-band digital data such that the value of the frequency band for generating the acoustic feedback is attenuated. Way. The method of claim 7, wherein
In the adjusting of the gain, the multi-band digital data is processed in real time using a notch filter scheme in a frequency domain on only a signal currently input through the microphone. delete The method of claim 7, wherein
In the step of adjusting the gain,
Attenuation gain is applied to the data of the maximum energy band of the multi-band digital data. The method of claim 10,
And applying attenuation gains to the peripheral band in a predetermined range relative to the maximum energy band. The method of claim 1,
The synthesis unit,
An IFFT processor for converting the multi-band digital data whose gain is adjusted by the gain controller into IFFT (Inverse Fast Fourier Transform) and converting the data into time axis data;
A window application unit for selecting valid data from an output of the IFFT processor;
An output buffer for sequentially storing and outputting the output of the window applying unit;
A D / A converter converting an output of the output buffer into an analog signal; And
The receiver for outputting sound in accordance with an output signal of the D / A converter
Acoustic feedback removal device comprising a. The method of claim 7, wherein
In the step of adjusting the gain,
Attenuation gain is calculated based on a ratio between the energy of the maximum energy band and the average of energy, and the same attenuation gain is applied to the data of the maximum energy band and the data of the peripheral band in a predetermined range for the maximum energy band. A method for removing acoustic feedback. The method of claim 7, wherein
In the step of adjusting the gain,
Attenuation gain is calculated based on a ratio between the energy of the maximum energy band and the average of the energy, wherein the attenuation gain is applied differently according to the frequency difference with the frequency of the maximum energy band. The method of claim 14,
And applying the largest attenuation gain to the data of the maximum energy band, and applying the attenuation gain different from the largest attenuation gain to the data of the peripheral band of the maximum energy band.

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