Method and apparatus for a hearing assistance system with adaptive bulk delay
View Patent ↗A hearing assistance system having adjustable bulk delay for cancellation of a time varying acoustic feedback path. The hearing assistance system including an FIR filter, coefficient update module, and delay rules module for programmable adaptive filtering. The hearing assistance system adjustable for continuous bulk delay adjustments. The hearing assistance system providing a number of coefficient update routines, including, but not limited to an LMS coefficient update process and a normalized LMS coefficient update process.
1. A hearing aid, comprising:
a microphone to receive sounds and produce analog signals representative of the received sounds;
a receiver for playing sound;
an analog-to-digital converter to convert the analog signals from the microphone into a digital representation;
a sound processor to process the digital representation and create a digital output for the receiver; and
an acoustic feedback estimator to generate an acoustic feedback estimate representing a time-varying acoustic feedback from the receiver to the microphone, the acoustic feedback estimate based on the digital output and an error signal based on a difference between the digital representation and the acoustic feedback estimate, the acoustic feedback estimator including an adaptive bulk delay to compensate for changes in the acoustic feedback signal, the adaptive bulk delay comprising:
a memory to receive the digital output, the memory including a plurality of memory locations for storing a plurality of digital samples and a pointer for pointing to certain digital samples;
a coefficient update module that receives the error signal and the digital samples and generates new filter coefficients;
a coefficient memory that stores the new filter coefficients and includes a coefficient pointer for pointing to certain new filter coefficients;
a filter that receives a delayed version of the digital output from the memory and the new filter coefficients; and
a delay rules module providing outputs for controlling the pointer of the memory and the coefficient pointer of the coefficient memory based on the new filter coefficients to adjust the adaptive bulk delay.
2. The hearing aid of claim 1 , further comprising:
a driver including a pulse density modulator to receive the processed error signal and drive the receiver to generate sounds.
3. The hearing aid of claim 1 , wherein the receiver includes a speaker.
4. The hearing aid of claim 1 , wherein a configuration of the memory employs linked lists.
5. The hearing aid of claim 1 , wherein the delay rules module includes storage for a number of consecutive coefficients and for a first coefficient position.
6. The hearing aid of claim 1 , wherein the memory includes a first-in-first-out (FIFO) data buffer.
7. The hearing aid of claim 1 , wherein the hearing aid is realized in a mix of hardware and firmware.
8. The hearing aid of claim 1 , wherein the hearing aid is realized substantially in hardware.
9. The hearing aid of claim 1 , wherein the hearing aid is realized substantially in software.
10. The hearing aid of claim 1 , wherein the coefficient update module is adapted for implementing an LMS coefficient update process.
11. The hearing aid of claim 1 , wherein the coefficient update module is adapted for implementing a normalized LMS coefficient update process.
12. The hearing aid of claim 1 , wherein the coefficient update module is adapted for implementing an affine projection update process.
13. The hearing aid of claim 1 , wherein the coefficient update module is adapted for implementing an RLS coefficient update process.
14. The hearing aid of claim 1 , wherein the filter is an FIR filter.
15. The hearing aid of claim 1 , wherein the filter is an IIR filter.