Adaptive residual feedback suppression
A hearing aid includes: an input transducer for generating an audio signal; a feedback suppression circuit configured for modelling a feedback path of the hearing aid; a subtractor for subtracting an output signal of the feedback suppression circuit from the audio signal to form a feedback compensated audio signal; a signal processor that is coupled to an output of the subtractor for processing the feedback compensated audio signal to perform hearing loss compensation; and a receiver that is coupled to an output of the signal processor for converting the processed feedback compensated audio signal into a sound signal; wherein the hearing aid further comprises a gain processor for performing gain adjustment of the feedback compensated audio signal based at least on an estimate of a residual feedback signal of the feedback compensated audio signal, wherein the estimate of the residual feedback signal is based at least on the audio signal.
1. A hearing aid comprising:
an input transducer for generating an audio signal;
a feedback suppression circuit configured for modelling a feedback path of the hearing aid;
a subtractor for subtracting an output signal of the feedback suppression circuit from the audio signal to form a feedback compensated audio signal;
a signal processor that is coupled to an output of the subtractor for processing the feedback compensated audio signal to perform hearing loss compensation; and
a receiver that is coupled to an output of the signal processor for converting the processed feedback compensated audio signal into a sound signal;
wherein the hearing aid further comprises a gain processor for performing gain adjustment of the feedback compensated audio signal based at least on an estimate of a residual feedback signal of the feedback compensated audio signal, wherein the estimate of the residual feedback signal is based at least on the audio signal, and wherein an amount of the gain adjustment is variable in response to a variability of the estimate of the residual feedback signal.
2. The hearing aid according to claim 1 , wherein the feedback suppression circuit is configured during an initialization of the hearing aid, and wherein the estimate of the residual feedback signal is further based on a configuration of the feedback suppression circuit achieved during the initialization of the hearing aid.
3. The hearing aid according to claim 1 , wherein the feedback suppression circuit has a configuration that is variable, and wherein the estimate of the residual feedback signal is further based on a configuration of the feedback suppression circuit as determined during a current operation of the hearing aid.
4. The hearing aid according to claim 1 , wherein the estimate of the residual feedback signal is further based on a gain value of the hearing aid.
5. The hearing aid according to claim 1 , wherein the feedback suppression circuit comprises an adaptive filter.
6. The hearing aid according to claim 1 , wherein the gain processor and the signal processor are configured to respectively perform the gain adjustment and the hearing loss compensation separately.
7. The hearing aid according to claim 1 , wherein the signal processor is configured to perform multi-band hearing loss compensation in a set of frequency bands k, and wherein the estimate of the residual feedback signal comprises estimates of the residual feedback signal in the frequency bands k.
8. The hearing aid according to claim 7 , wherein the estimate of the residual feedback signal includes an estimate of an adaptive broad-band contribution β.
9. A hearing aid comprising:
an input transducer for generating an audio signal;
a feedback suppression circuit configured for modelling a feedback path of the hearing aid;
a subtractor for subtracting an output signal of the feedback suppression circuit from the audio signal to form a feedback compensated audio signal;
a signal processor that is coupled to an output of the subtractor for processing the feedback compensated audio signal to perform hearing loss compensation; and
a receiver that is coupled to an output of the signal processor for converting the processed feedback compensated audio signal into a sound signal;
wherein the hearing aid further comprises a gain processor for performing gain adjustment of the feedback compensated audio signal based at least on an estimate of a residual feedback signal of the feedback compensated audio signal, wherein the estimate of the residual feedback signal is based at least on the audio signal;
wherein the signal processor is configured to perform multi-band hearing loss compensation in a set of frequency bands k, and wherein the estimate of the residual feedback signal comprises estimates of the residual feedback signal in the frequency bands k;
wherein the estimate of the residual feedback signal includes an estimate of an adaptive broad-band contribution β; and
wherein the estimates R k of the residual feedback signal in the respective frequency bands k is given by
| R k |=β|A k ∥B k |
and an amount of the gain adjustment α k is calculated from:
α
k
2
=
1
(
1
+
β
2
G
k
2
A
k
2
B
k
2
)
wherein
β is a scaling term relating the residual feedback signal to a feedback reference,
A k is a feedback reference gain obtained using the feedback suppression circuit, and
B k is a contribution from the audio signal.
10. The hearing aid according to claim 9 , wherein the feedback suppression circuit comprises an adaptive filter, and wherein β is calculated from:
β
=
(
(
c
s
h
emp
→
*
w
→
)
q
+
(
c
d
h
emp
→
*
(
w
→
-
w
ref
→
)
)
q
)
1
q
σ
norm
wherein
q is an integer,
∥ ∥ indicates a p-norm of a vector, p is a positive integer,
c s is a scaling factor relating to an accuracy of the feedback suppression circuit in modelling the feedback path in static situations,
c d is a scaling factor relating to an accuracy of the feedback suppression circuit in modelling the feedback path in dynamic situations,
{right arrow over (h emp )} represents a filter for emphasizing certain frequencies,
{right arrow over (w)} is the coefficient vector of the adaptive filter,
{right arrow over (w ref )} is the reference coefficient vector of the adaptive filter, and
σ norm is a low-pass filtered feedback suppression circuit norm σ norm =lpf(∥{right arrow over (h emp )}*{right arrow over (w)}∥).
11. The hearing aid according to claim 10 , wherein q is equal to two.
12. The hearing aid according to claim 10 , wherein {right arrow over (h emp )} is equal to one.
13. The hearing aid according to claim 10 , wherein the p-norm is 1-norm.
14. The hearing aid according to claim 1 , further comprising attack and release filters configured for smoothing process parameters in the gain processor.
15. A method of suppressing residual feedback, comprising:
converting an acoustic signal into an audio signal;
modelling a feedback path using a feedback suppression circuit receiving an input signal based on the audio signal, and generating an output signal;
subtracting the output signal of the feedback suppression circuit from the audio signal to form a feedback compensated audio signal;
determining an estimate of a residual feedback signal part of the feedback compensated audio signal based at least on the audio signal; and
applying a gain to the feedback compensated audio signal based at least on the estimate;
wherein the estimate of the residual feedback signal part is based at least on the audio signal; and
wherein an amount of the gain is variable in response to a variability of the estimate of the residual feedback signal.
16. The method according to claim 15 , further comprising monitoring the feedback path, wherein the estimate of the residual feedback signal part is based on a result from the act of monitoring.