US-12627936-B2 - Real-time Multirate Multiband Amplification for hearing aids

Abstract

In accordance with a method for performing frequency subchannelization, a digital signal is received at an original sampling rate. A plurality of multirate frequency channels is produced by dividing the digital signal into an integer number of multirate frequency channels such that a sampling rate of each of the multirate frequency channels is proportional to a center frequency of the frequency channel. Signal processing is performed on each of the multirate frequency channels. The original sampling rate is reconstructed using the multirate frequency channels.

Inventors

• Harinath Garudadri
• Alice SOKOLOVA
• Frederic HARRIS

Assignees

• THE REGENTS OF THE UNIVERSITY OF CALIFORNIA

Dates

Publication Date

20260512

Application Date

20221031

Claims (11)

1. 1 . A method for performing frequency sub channelization, comprising: receiving a digital signal at an original sampling rate; producing a plurality of multirate frequency channels by dividing the digital signal into an integer number of multirate frequency channels such that a sampling rate of each of the multirate frequency channels is proportional to a center frequency of the frequency channel; performing signal processing on each of the multirate frequency channels; and reconstructing the original sampling rate using the multirate frequency channels.
2. 2 . The method of claim 1 wherein the digital signal is a digital audio signal and further wherein dividing the digital audio signal into an integer number of multirate frequency channels includes dividing the digital audio signal into an integer number of multirate frequency channels per octave.
3. 3 . The method of claim 1 further comprising recombining the upsampled multirate frequency channels.
4. 4 . The method of claim 1 wherein the signal processing performed on each of the multirate frequency sub-bands includes automatic gain control (AGC) for wide dynamic range compression (WDRC).
5. 5 . The method of claim 4 wherein the AGC for WDRC uses a closed form relationship between user compression parameters and compression gains and compression attack and release times.
6. 6 . The method of claim 1 wherein each respective multirate frequency channel is sampled at a rate that is proportional to a frequency of an octave to which the multirate frequency channel belongs.
7. 7 . A hearing aid device, comprising: a microphone configured to receive an audible input signal from an environment and convert the audible input signal to an electrical audio input signal; a multi-band hearing aid processing circuit configured for processing the electrical audio input signal, the multi-band hearing aid processing circuit being further configured to: receive the electrical audio input signal and produce a digital signal at an original sampling rate; produce a plurality of multirate frequency channels that divide the digital signal into an integer number of multirate frequency channels per octave; perform envelope detection on each of the multirate frequency channels; perform automatic gain control (AGC) for WDRC using the detected envelope of each of the multirate frequency channels using an algorithm that has a closed form relationship between user compression parameters and compression gains and compression attack and release times; upsample the multirate frequency channels to the original sampling rate; recombine the upsampled multirate frequency channels to produce an electrical audio output signal; and a speaker configured to receive the electrical audio output signal from the multi-band hearing aid processing circuit and emit an audible output signal into an ear of a user.
8. 8 . The hearing aid device of claim 7 wherein the envelope detection is performed using a Hilbert Transform.
9. 9 . The hearing aid device of claim 8 wherein the Hilbert Filter utilized in the Hilbert Transform is a minimum phase Hilbert Filter.
10. 10 . The hearing aid device of claim 7 wherein the envelope detection is performed using a peak detector.
11. 11 . The hearing aid device of claim 7 wherein the envelope detection is performed using a frame-based power estimation technique.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Application Ser. No. 63/273,512, filed Oct. 29, 2022, the contents of which are incorporated herein by reference. GOVERNMENT FUNDING This invention was made with government support under DC015046 and DC015436 awarded by the National Institutes of Health, and under IIS1838830 awarded by the National Science Foundation. The government has certain rights in the invention. BACKGROUND Studies have shown that only about one-third of individuals who have hearing loss utilize a hearing aid. Among those individuals, around one-third do not use their hearing aids regularly. The main reason for this disuse is often the dissatisfaction with the speech quality offered by modern hearing aids, especially in noisy environments where hearing-impaired individuals need them the most. Achieving music appreciation with hearing aids is an even greater challenge. One highly effective approach for improving the audibility of sound for hearing impaired users is called Wide Dynamic Range Compression (WDRC), which is the amplification and reduction of the dynamic range, or volume swing, of an audio signal. WDRC involves amplifying quiet signals to improve audibility, and simultaneously decreasing the volume of loud signals to reduce discomfort to a hearing-impaired user. Human hearing, however, is inherently frequency-dependent. The human cochlea perceives finer pitch variation at lower frequencies than at higher frequencies. Additionally, hearing loss is also typically frequency dependent, affecting certain frequency ranges more than others. For this reason, the compression gains needed to compensate for hearing loss vary across different frequency bands, necessitating a multiband approach to WDRC. Studies have shown that a greater number of frequency bins increases researchers' flexibility, especially for unusual hearing loss patterns. SUMMARY In one aspect a Real-time Multirate Multiband Amplification system is presented herein which addresses the need for finer, more precise gain control in a hearing aid device. The system design provides higher flexibility and accuracy than currently available on open-source platforms. In one implementation the system includes: 1) A Multirate Audiometric Filter Bank, offering highly accurate low-latency subband decomposition which can be used for a variety of hearing enhancement algorithms. In this paper, we present a half-octave realization, centered at the standard audiometric frequencies of 250, 375, 500, 1000, 1500, 2000, 3000, 4000, 6000, and 8000 Hz.2) A Multirate Automatic Gain Control system for WDRC that accurately fulfills the static and dynamic properties specified by audiologists, which include steady state Gains, as well as the dynamics of the Gains realized as the attack and release times of the said Gains in each subband. This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a block diagram of one example of a subband amplification system in accordance with the systems and principles described herein. FIG. 2 shows the magnitude response and composite responses for one example of a multirate filter bank. FIG. 3 shows a block diagram of one example of the multirate filter bank. FIG. 4 compares a single-stage (top) and a cascaded implementation of a 1:8 upsampler (bottom). FIG. 5 compares a conventional and a polyphase 2:1 downsampler in one illustrative example. FIG. 6 compares the impulse responses of a linear phase implementation (top) and a minimum phase implementation (bottom) of the illustrative multirate filter bank. FIG. 7 is a function block diagram illustrating the general concept of Automatic Gain Control for WDRC. FIG. 8 shows the waveform and computed envelope of the word “please” in the 375 Hz band, spoken by a female voice. FIG. 9 shows a WDRC curve in which the ANSI 3.22 standard attack and release times of hearing aids are measured using a sinusoidal step input changing from 55 dB to 90 dB. FIG. 10 illustrates the ANSI standard attack time, which is measured as the time it takes for the overshoot to settle within 3 dB of steady state and the release time, which is measured as the time is takes for the undershoot to settle within 4 dB of steady state. FIG. 11 is a block diagram of one example of the AGC algorithm. FIG. 12 shows some of the ISMADHA standard pure tone audiograms and an example of the obtained target input/output amplification curves for each audiogram at 1 kHz. FIG. 13 shows Verif