Tonality-driven feedback canceler adaptation
Disclosed herein, among other things, are apparatus and methods for tonality-driven feedback canceler adaptation for hearing devices. Various embodiments include a method of signal processing an input signal in a hearing device to mitigate entrainment, the hearing device including a receiver and a microphone. The method includes detecting strength of tonality of the input signal by estimating a second derivative of subband phase of the input signal, and adjusting parameters of an adaptive feedback canceler of the hearing device based on the detected tonality.
1. A method of signal processing an input signal in a hearing device to mitigate entrainment, the hearing device including a receiver and a microphone, the method comprising:
detecting strength of tonality of the input signal by estimating a second derivative of subband phase of the input signal by comparing a first block-to-block difference of tonal energy in of a first sequence of blocks to a second block-to-block difference of tonal energy of a second sequence of blocks, wherein the first sequence and the second sequence overlap; and
adjusting parameters of an adaptive feedback canceler of the hearing device based on the detected strength of tonality.
2. The method of claim 1 , wherein detecting strength of tonality of the input signal by estimating the second derivative of subband phase of the input signal includes computing block-to-block difference in subband phase over at least three subband blocks of the input signal.
3. The method of claim 1 , wherein detecting strength of tonality of the input signal by estimating the second derivative of subband phase of the input signal includes using weighted overlap-add (WOLA) filter subbands.
4. The method of claim 1 , wherein adjusting parameters of an adaptive feedback canceler of the hearing device includes reducing an adaptation rate when a tonal signal is detected.
5. The method of claim 1 , wherein adjusting parameters of an adaptive feedback canceler of the hearing device includes increasing an adaptation rate when a tonal signal is detected.
6. The method of claim 1 , wherein adjusting parameters of an adaptive feedback canceler of the hearing device includes adjusting or constraining adaptation step size.
7. The method of claim 1 , wherein the estimated second derivative of subband phase of the input signal in one subband or frequency channel is compared with an estimated second derivative of subband phase of the input signal in other subbands or frequency channels, such that tonal signals are distinguished from tones due to feedback oscillation, and parameters of an adaptive feedback canceler of the hearing device are adjusted based on the distinction.
8. The method of claim 1 , wherein the estimated second derivative of subband phase of the input signal in one subband or frequency channel is compared with an estimated second derivative of subband phase of the input signal in other subbands or frequency channels, such that transient or impulsive input signal are detected, and the adaptation of the adaptive feedback canceler is temporarily halted or constrained to reduce estimation error introduced by the transient or impulsive input signals.
9. The method of claim 1 , comprising adjusting phase modulation based on the detected tonality.
10. The method of claim 9 , wherein adjusting phase modulation includes reducing phase modulation rate when a tonal signal is detected.
11. The method of claim 9 , wherein adjusting phase modulation includes increasing phase modulation rate when a tonal signal is detected.
12. The method of claim 1 , wherein the hearing device is a hearing aid.
13. The method of claim 1 , wherein detecting strength of tonality of the input signal includes detecting strength of tonality in a subband containing multiple tones.
14. A hearing device, comprising:
a microphone configured to receive audio signals; and
a processor configured to process the audio signals to correct for a hearing impairment of a wearer, the processor further configured to:
detect strength of tonality of the audio signals by estimating a second derivative of subband phase of the audio signals by comparing a first block-to-block difference of tonal energy in of a first sequence of blocks to a second block-to-block difference of tonal energy of a second sequence of blocks, wherein the first sequence and the second sequence overlap; and
adjust parameters of an adaptive feedback canceler of the hearing device based on the detected strength of tonality.
15. The hearing device of claim 14 , wherein the hearing device is a hearing aid.
16. The hearing device of claim 15 , wherein the hearing aid is a behind-the-ear (BTE) hearing aid.
17. The hearing device of claim 15 , wherein the hearing aid is an in-the-canal (ITC) hearing aid.
18. The hearing device of claim 15 , wherein the hearing aid is a completely-in-the-canal (CIC) hearing aid.
19. The hearing device of claim 15 , wherein the hearing aid is a receiver-in-canal (RIC) hearing aid.
20. The hearing device of claim 15 , wherein the hearing aid is an invisible-in-canal (IIC) hearing aid.