Abstract:

This study investigated whether the relative amount of speech information contained in specific frequency regions of the speech spectrum differs between implantees and normal-hearing subjects, or between implantees having different speech perception abilities. In addition, the relationship between the amount of speech information implantees perceived in each frequency region and their ability to discriminate adjacent electrodes was investigated. Fifteen subjects using the Nucleus CI-22M implant (SPECTRA-22 processor/SPEAK strategy), and 16 normal-hearing listeners participated. Articulation index procedures were used to measure the amount of speech information perceived in different frequency bands. Results showed that, compared to the normal-hearing listeners, the implantees obtained less speech information in all frequency regions, but more information in the higher, compared to the lower, frequencies. Correlation analysis showed that electrode discrimination and perceivable speech information were correlated in the lower frequency regions, but not in the highest region, suggesting that the perception of speech information in the lower regions requires the ability to discriminate electrodes, while the perception of high-frequency information does not. These findings predict that speech perception may be improved by changing the assignment of frequencies to electrode positions to provide better discrimination of low- to mid-frequency speech information.