Adaptive, programmable signal processing and filtering for hearing aids
First Claim
1. A digital signal processing hearing aid system comprising:
- (a) input means for providing an electrical input signal corresponding to a sound signal;
(b) analog to digital converter means for converting the input signal from the input means to input signal digital data at a selected sample rate;
(c) digital signal processing means for receiving the input signal digital data from the analog to digital converter means and providing processed output data, the digital signal processing means including;
(1) means for analyzing the input signal data and estimating the energy contained in a plurality of selected frequency bands which cover the range of frequency content of the input signal data, wherein the means for analyzing the input signal data includes a first high pass digital filter for passing the higher half of the input signal frequency range, a first low pass digital filter for passing the lower half of the input signal frequency range and providing a second frequency range signal data, a second high pass digital filter selected to pass the higher half of the second frequency range signal and a second low pass digital filter selected to pass the lower half of the second frequency range signal to provide a third frequency range signal, a third high pass digital filter selected to pass the higher half of the third frequency range signal and a third low pass digital filer selected to pass the lower half of the third frequency range signal to provide a fourth frequency range signal, the fourth high pass filter selected to pass the higher half of the fourth frequency range signal and a fourth low pass digital filter selected to pass the lower half of the fourth frequency range signal, and wherein the means for analyzing further includes means for estimating the energy in the data corresponding to the outputs of the first, second, third, and fourth high pass filters and the fourth low pass filter;
(2) gain calculation means for calculating a gain for each band which is a function of estimated energy in each band;
(3) digital spectral filter means, having a plurality of filter coefficients which are changeable, for receiving the input signal digital data and providing spectrally shaped output data for output from the digital signal processing means;
(4) coefficient calculation means for calculating the coefficients of the digital spectral filter means based on the gains for each band calculated by the gain calculation means, the coefficients of the digital spectral filter means being periodically changed to the new coefficients calculated by the coefficient calculation means;
(d) digital to analog converter means for converting the processed output data from the digital signal processing means to an analog signal; and
(e) means for converting the analog signal to a corresponding sound.
2 Assignments
0 Petitions
Accused Products
Abstract
A hearing aid system utilizes digital signal processing to correct for the hearing deficit of a particular user and to maximize the intelligibility of the desired audio signal relative to noise. An analog signal from a microphone is converted to digital data which is operated on by a digital signal processor, with the output of the digital signal processor being converted back to an analog signal which is amplified and provided to the user. The digital signal processor includes a time varying spectral filter having filter coefficients which can be varied on a quasi-real time basis to spectrally shape the signal to match the hearing deficit of the user and to accommodate ambient signal and noise levels. The coefficients of the spectral filter are determined by estimating the energy in several frequency bands within the frequency range of the input signal, and using those energy estimates to calculate desired gains for the frequency bands and corresponding spectral filter coefficients. The spectral energy analysis may be carried out using pairs of high pass and low pass digital filters in cascade relation, with the output of each low pass filter being provided to the next pair of high pass and low pass filters. The rate at which output data is provided from the filters in each pair may be reduced from the sample rate of input data by one half for succeeding pairs of filters in the cascade to thereby reduce the computation time required.
447 Citations
58 Claims
-
1. A digital signal processing hearing aid system comprising:
-
(a) input means for providing an electrical input signal corresponding to a sound signal; (b) analog to digital converter means for converting the input signal from the input means to input signal digital data at a selected sample rate; (c) digital signal processing means for receiving the input signal digital data from the analog to digital converter means and providing processed output data, the digital signal processing means including; (1) means for analyzing the input signal data and estimating the energy contained in a plurality of selected frequency bands which cover the range of frequency content of the input signal data, wherein the means for analyzing the input signal data includes a first high pass digital filter for passing the higher half of the input signal frequency range, a first low pass digital filter for passing the lower half of the input signal frequency range and providing a second frequency range signal data, a second high pass digital filter selected to pass the higher half of the second frequency range signal and a second low pass digital filter selected to pass the lower half of the second frequency range signal to provide a third frequency range signal, a third high pass digital filter selected to pass the higher half of the third frequency range signal and a third low pass digital filer selected to pass the lower half of the third frequency range signal to provide a fourth frequency range signal, the fourth high pass filter selected to pass the higher half of the fourth frequency range signal and a fourth low pass digital filter selected to pass the lower half of the fourth frequency range signal, and wherein the means for analyzing further includes means for estimating the energy in the data corresponding to the outputs of the first, second, third, and fourth high pass filters and the fourth low pass filter; (2) gain calculation means for calculating a gain for each band which is a function of estimated energy in each band; (3) digital spectral filter means, having a plurality of filter coefficients which are changeable, for receiving the input signal digital data and providing spectrally shaped output data for output from the digital signal processing means; (4) coefficient calculation means for calculating the coefficients of the digital spectral filter means based on the gains for each band calculated by the gain calculation means, the coefficients of the digital spectral filter means being periodically changed to the new coefficients calculated by the coefficient calculation means; (d) digital to analog converter means for converting the processed output data from the digital signal processing means to an analog signal; and (e) means for converting the analog signal to a corresponding sound. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
-
-
26. A digital signal processing hearing aid system comprising:
-
(a) input means for providing an electrical signal corresponding to a sound signal; (b) analog to digital converter means for converting the signal from the input means to digital data at a selected sample rate; (c) digital signal processing means for receiving the input signal digital data from the analog to digital converter means and providing processed output data, the digital signal processing means including; (1) N pairs of high pass and low pass digital filters, the high pass filter in each pair selected to pass the highest half of the frequency range of the input signal to the pair and the low pass filter in each pair selected to pass the lowest half of the frequency range of the input signal to the pair, the pairs of filters cascaded so that the input signal to each pair after the first pair is the output of the low pass filter of the prior pair of filters, and means for estimating the energy in the frequency bands corresponding to the outputs of the N high pass filters and the last low pass filter, where N is at least two; (2) gain calculation means for calculating a gain for each band which is a function of the estimated energy in each band; (3) digital spectral filter means, having a plurality of filter coefficients which are changeable, for receiving the input signal data and providing spectrally shaped output data for output from the digital signal processing means; (4) coefficient calculation means for calculating the coefficients of the digital spectral filter means based on the gains for each band calculated by the gain calculation means, the coefficients of the digital spectral filter means being periodically changed to the new coefficients calculated by the coefficient calculation means; (d) digital to analog converter means for converting the processed output data from the digital signal processing means to an analog signal; and (e) means for converting the analog signal to a corresponding sound. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)
-
-
53. A digital spectral analysis filter comprising:
-
(a) input means for providing an electrical signal corresponding to a sound signal; (b) analog to digital converter means for converting the signal from the input means to digital data at a selected sample rate; (c) digital signal processing means for receiving the input signal digital data from the analog to digital converter means and providing processed output data, the digital signal processing means including N pairs of high pass and low pass digital filters, the high pass filter in each pair selected to pass the highest half of the frequency range of the input signal to the pair and the low pass filter in each pair selected to pass the lowest half of the frequency range of the input signal to the pair, the pairs of filters cascaded so that the input signal to each pair after the first pair is the output of the low pass filter of the prior pair of filters, where N is at least two, and wherein the computation of output values of the first pair of high pass and low pass filters is performed at half the sample rate and the computation of output values for succeeding pairs of high pass and low pass filters is performed at a rate which is a fraction of the sample rate equal to 1/2n+1, where n is the number of prior filter pairs. - View Dependent Claims (54, 55, 56, 57, 58)
-
Specification