Outer hair cell stimulation model for the use by an intra—cochlear implant
View Patent ↗Contrast between various frequency components of sound is enhanced through a lateral suppression strategy to provide increased speech perception in the electrically stimulated cochlea. A received audio signal is divided into a plurality of input signals, wherein each input signal is associated with a frequency band. A plurality of envelope signals are generated by determining the envelope of each of a plurality of the input signals. At least one of the envelope signals is scaled in accordance with a scaling factor to generate at least one scaled envelope signal. An output signal is generated by combining at least one envelope signal with at least one scaled envelope signal, and the cochlea is stimulated based on the generated output signal. The lateral suppression strategy can be applied to one or more frequency bands using scaled amplitude signals associated with one or more neighboring frequency bands.
1. A method of generating a cochlear stimulation signal, the method comprising:
dividing an audio signal into a plurality of input signals, wherein each input signal is associated with a frequency band;
generating a plurality of envelope signals, including at least a first and a second envelope signal, by determining an envelope of each of at least two input signals, each input signal being associated with a corresponding frequency band;
scaling at least one of the envelope signals in accordance with a scaling factor to generate at least one scaled envelope signal; and
combining at least one envelope signal with at least one scaled envelope signal to generate an output signal, wherein the at least one envelope signal and the at least one scaled envelope signal are associated with different frequency bands.
2. The method of claim 1 , further comprising:
multiplying the first envelope signal by a first weighting factor; and
multiplying the second envelope signal by a second weighting factor.
3. The method of claim 1 , wherein scaling at least one of the envelope signals further comprises:
determining a separation between a first frequency band and a second frequency band; and
selecting a scaling factor based on the separation.
4. The method of claim 1 , further comprising:
scaling a plurality of envelope signals associated with frequency bands that neighbor a first frequency band to generate a plurality of scaled envelope signals; and
combining the envelope signal associated with the first frequency band with the plurality of scaled envelope signals to generate an output signal associated with the first frequency band.
5. The method of claim 1 , further comprising rectifying an input signal prior to determining the envelope of the input signal.
6. The method of claim 5 , further comprising full-wave rectifying the input signal.
7. The method of claim 1 , further comprising:
setting an average amplitude associated with an input signal to zero at the beginning of a frame; and
determining the average amplitude associated with the input signal for the frame.
8. The method of claim 1 , wherein the generated output signal comprises an acoustic signal.
9. The method of claim 8 , further comprising:
mapping the generated output signal to an electrical signal; and
applying the electrical signal to one or more electrode pairs of a cochlear implant.
10. The method of claim 1 , wherein the generated output signal is associated with a first frequency band.
11. The method of claim 1 , wherein combining further comprises generating an output signal in accordance with a frequency modulated stimulation strategy.
12. The method of claim 1 , wherein combining further comprises subtracting the at least one scaled envelope signal from the at least one envelope signal.
13. The method of claim 1 , wherein scaling at least one of the envelope signals reduces the magnitude of the envelope signal.
14. The method of claim 1 , wherein each of the plurality of envelope signals represents an average amplitude of a corresponding input signal.
15. The method of claim 1 , wherein scaling in accordance with a scaling factor comprises using a scaling factor which ranges from 0 to 1.
16. An apparatus for generating a cochlear stimulation signal, the apparatus comprising:
a plurality of filters configured to divide an audio signal into a plurality of input signals, wherein each input signal is associated with a frequency band;
a plurality of envelope detectors configured to generate a plurality of envelope signals, including at least a first and a second envelope signal, by determining an envelope of each of at least two input signals, each input signal being associated with a corresponding frequency band; and
circuitry configured to scale at least one of the envelope signals in accordance with a scaling factor to generate at least one scaled envelope signal and to combine at least one envelope signal with at least one scaled envelope signal to generate an output signal, wherein the at least one envelope signal and the at least one scaled envelope signal are associated with different frequency bands.
17. The apparatus of claim 16 , wherein the circuitry is further configured to:
multiply the first envelope signal by a first weighting factor; and
multiply the second envelope signal by a second weighting factor.
18. The apparatus of claim 16 , wherein the circuitry is further configured to:
determine a separation between a first frequency band and a second frequency band; and
select a scaling factor based on the separation.
19. The apparatus of claim 16 , wherein the circuitry is further configured to:
scale a plurality of envelope signals associated with frequency bands that neighbor a first frequency band to generate a plurality of scaled envelope signals; and
combine the envelope signal associated with the first frequency band with the plurality of scaled envelope signals to generate an output signal associated with the first frequency band.
20. The apparatus of claim 16 , further comprising:
a rectifier configured to rectify an input signal prior to the envelope detector determining the envelope of the input signal.
21. The apparatus of claim 20 , wherein the rectifier comprises a full-wave rectifier.
22. The apparatus of claim 16 , wherein the envelope detector is configured to:
set an average amplitude associated with an input signal to zero at the beginning of a frame; and
determine the average amplitude associated with the input signal for the frame.
23. The apparatus of claim 16 , wherein the generated output signal comprises an acoustic signal.
24. The apparatus of claim 23 , wherein the circuitry is further configured to:
map the generated output signal to an electrical signal; and
apply the electrical signal to one or more electrode pairs of a cochlear implant.
25. The apparatus of claim 23 , wherein the generated output signal is associated with a first frequency band.
26. The apparatus of claim 16 , wherein the circuitry is further configured to generate the output signal in accordance with a frequency modulated stimulation strategy.
27. The apparatus of claim 16 , wherein the circuitry is further configured to subtract the at least one scaled envelope signal from the at least one envelope signal.
28. The apparatus of claim 16 , wherein scaling at least one of the envelope signals reduces the magnitude of the envelope signal.
29. The apparatus of claim 16 , wherein each of the plurality of envelope detectors is configured to generate an envelope signal representing an average amplitude of a corresponding input signal.
30. The apparatus of claim 16 , wherein the circuitry comprises one or more of a programmable logic device, a field programmable gate array, an application-specific integrated circuit, and a general purpose processor executing programmed instructions.
31. The apparatus of claim 16 , wherein the scaling factor ranges from 0 to 1.