Reduction of transient sounds in hearing implants
A method is described for generating electrode stimulation signals for electrode contacts in a cochlear implant electrode array. An input audio signal is processed to generate band pass channel signals that each represent an associated band of audio frequencies. A channel envelope is extracted from each channel signal. The input audio signal and the channel envelopes are processed to produce transient reduced envelopes based on: i. determining for each channel envelope a normalized channel-specific transient indicator characterizing transient noise present in the channel signal, ii. determining a combined transient indicator as a function of the channel-specific transient indicators, and iii. applying a channel-specific gain to the channel envelopes as a function of the combined transient indicator to produce the transient reduced envelopes. The transient reduced envelopes are then used to generate electrode stimulation signals to the electrode contacts.
1. A method of generating electrode stimulation signals for electrode contacts in a cochlear implant electrode array, the method comprising:
processing an input audio signal to generate a plurality of band pass channel signals each representing an associated band of audio frequencies;
extracting a channel envelope from each channel signal;
processing the input audio signal and the channel envelopes to produce transient reduced envelopes based on:
i. determining for each channel envelope a normalized channel-specific transient indicator characterizing transient noise present in the channel signal,
ii. determining a combined transient indicator as a function of the channel-specific transient indicators, and
iii. applying a channel-specific gain to the channel envelopes as a function of the combined transient indicator to produce the transient reduced envelopes; and
using the transient reduced envelopes to generate electrode stimulation signals to the electrode contacts.
2. A method according to claim 1 , wherein the channel-specific transient indicator is based on a proportion of power of the channel envelope to power of the input audio signal.
3. A method according to claim 1 , wherein the channel-specific transient indicator is based on high-pass filtering the channel envelope.
4. A method according to claim 1 , wherein the combined transient indicator is based on a combined product of the channel-specific transient indicators.
5. A method according to claim 1 , wherein the combined transient indicator is based on a dependent function of the channel signals.
6. A method according to claim 5 , wherein the function reflects a limited frequency sub-range of the channel signals.
7. A method according to claim 1 , wherein the channel-specific gains are based on a single common gain function.
8. A method according to claim 1 , wherein the channel-specific gains are based on a filter applied to the channel envelopes.
9. A method according to claim 1 , wherein the channel specific gains reflect a signal-dependent suppression duration.
10. A method according to claim 1 , further comprising:
applying a stationary noise reduction process to the channel envelopes before producing the transient reduced envelopes.
11. An implantable signal processing arrangement for generating electrode stimulation signals for electrode contacts in a cochlear implant electrode array, the arrangement comprising:
a filter bank pre-processor configured to process an input audio signal to generate a plurality of band pass channel signals each representing an associated band of audio frequencies;
a channel envelope module configured to extract a channel envelope from each channel signal;
a transient reduction module configured to process the input audio signal and the channel envelopes to produce transient reduced envelopes based on:
i. determining for each channel envelope a normalized channel-specific transient indicator characterizing transient noise present in the channel signal,
ii. determining a combined transient indicator as a function of the channel-specific transient indicators, and
iii. applying a channel-specific gain to the channel envelopes as a function of the combined transient indicator to produce the transient reduced envelopes; and
a stimulation signal generator configured to use the transient reduced envelopes to generate electrode stimulation signals to the electrode contacts.
12. An arrangement according to claim 11 , wherein the transient reduction module determines the channel-specific transient indicators based on a proportion of power of the channel envelope to power of the input audio signal.
13. An arrangement according to claim 11 , wherein the transient reduction module determines the channel-specific transient indicator based on high-pass filtering the channel envelope.
14. An arrangement according to claim 11 , wherein the transient reduction module determines the combined transient indicator based on a combined product of the channel-specific transient indicators.
15. An arrangement according to claim 11 , wherein the transient reduction module determines the combined transient indicator based on a dependent function of the channel signals.
16. An arrangement according to claim 15 , wherein the function reflects a limited frequency sub-range of the channel signals.
17. An arrangement according to claim 11 , wherein the transient reduction module bases the channel-specific gains on a single common gain function.
18. An arrangement according to claim 11 , wherein the transient reduction module bases the channel-specific gains on a filter applied to the channel envelopes.
19. An arrangement according to claim 11 , wherein the transient reduction module applies channel specific gains that reflect a signal-dependent suppression duration.
20. An arrangement according to claim 11 , further comprising:
a stationary noise reduction module before the transient noise reduction module configured to apply a stationary noise reduction process to the channel envelopes.