Spectral contrast enhancement in a cochlear implant speech processor

1. A method of adjusting a speech processing strategy, the method comprising:

determining a transfer function of a cochlear implant user by administering a psychophysical test to the cochlear implant user that determines a smallest detectable spectral contrast as a function of frequency, wherein determining the smallest detectable spectral contrast comprises analyzing the cochlear implant user's ability to discriminate between frequencies in a spectrum;

selecting an enhancement filter function that matches the determined transfer function;

generating filter parameters of the enhancement filter function based on the transfer function; and

adjusting a speech processing strategy based on the generated filter parameters.

2. The method of claim 1 , wherein selecting the enhancement filter function further comprises comparing the transfer function of the cochlear implant user against a transfer function of a person with normal hearing and determining a ratio of the two transfer functions.

3. The method of claim 2 , wherein generating the filter parameters further comprises determining σ, G max and G min , wherein σ represents a width of the filter and G max and G min represents scaling and offset of the filter.

4. The method of claim 3 , wherein adjusting the speech processing strategy further comprises adjusting an outer hair cell model based on the filter parameters.

5. The method of claim 4 , wherein adjusting the outer hair cell model further comprises determining a plurality of lateral suppression coefficients based on the filter parameters.

6. The method of claim 1 , wherein generating the filter parameters further comprises fitting the enhancement filter function to the transfer function.

7. A system for adjusting a speech processing strategy, the system comprising:

a fitting system operative to

determine a transfer function of a cochlear implant user by administering a psychophysical test to the cochlear implant user that determines a smallest detectable spectral contrast as a function of frequency, wherein to determine the smallest detectable spectral contrast, the fitting system analyzes the cochlear implant user's ability to discriminate between frequencies in a spectrum;

select an enhancement filter function that matches the transfer function;

generate filter parameters of the enhancement filter function based on the transfer function; and

adjust a speech processing strategy based on the generated filter parameters.

8. The system of claim 7 further comprising a sound source operative to communicate with the fitting system and to output a known sound signal.

9. The system of claim 8 , wherein the fitting system further comprises a computer system including a personal computer, a laptop, or a portable computing device operative to communicate with a cochlear implant sound processing system and the sound source.

10. The system of claim 7 , wherein the fitting system is a portable system operative to facilitate adjustment of the speech processing strategy by the cochlear implant user.

11. The system of claim 7 , wherein the fitting system is further operative to compare the transfer function of the cochlear implant user against a transfer function of a person with normal hearing and to determine a ratio of the two transfer functions.

12. The system of claim 7 , wherein the fitting system is further operative to determine filter parameters including σ, G max , and G min , wherein σ represents a width of the filter and G max and G min represent scaling and offset of the filter.

13. The system of claim 12 , wherein the fitting system is further operative to adjust an outer haircell model based on the filter parameters.

14. The system of claim 13 , wherein adjusting the outer haircell model further comprises adjusting a plurality of lateral suppression coefficients based on the filter parameters.

15. The system of claim 7 , wherein generating the filter parameters further comprises fitting the enhancement filter function to the transfer function.

16. A spectral contrast enhancing method comprising:

determining for a cochlear implant user a transfer function comprising a smallest detectable spectral contrast as a function of frequency, wherein the smallest detectable spectral contrast is determined at least in part by analyzing the cochlear implant user's ability to discriminate between frequencies in a spectrum;

comparing the determined transfer function of the cochlear implant user to a transfer function of a person having normal hearing, wherein a ratio of the two transfer functions determines an enhancement factor desired for the cochlear implant user;

generating filter parameters based on the transfer function and the enhancement factor; and

adjusting a speech processing strategy based on the generated filter parameters, wherein the speech processing strategy comprises an outer hair cell model.

17. A machine readable medium storing instructions operative to cause a data processing apparatus to perform operations comprising:

determine for a cochlear implant user a transfer function comprising a smallest detectable spectral contrast as a function of frequency, the determination made at least in part by analyzing the cochlear implant user's ability to discriminate between frequencies in a spectrum;

compare the determined transfer function of the cochlear implant user to a transfer function of a person having normal hearing, wherein a ratio of the two transfer functions determines an enhancement factor desired for the cochlear implant user;

generate filter parameters based on the transfer function and the enhancement factor; and

adjust a speech processing strategy based on the generated filter parameters, wherein the speech processing strategy comprises an outer hair cell model.