Effects of Speech Processing Strategy on Chinese Tone Recognition by Nucleus-24 Cochlear Implant Users

In Brief Objective: To evaluate the effects of speech processing strategy on Chinese tone recognition by Nucleus-24 cochlear implant users. Methods: Recognition of Chinese tones was measured with the spectral peak (SPEAK), advanced combination encoders (ACE), and continuous interleaved sampling (CIS) strategies in nine Nucleus-24 cochlear implant users. Recognition of Chinese sentences was also measured with the ACE strategy (1200 pulse-per-sec on each electrode). As the stimulation rate in the SPEAK processor is fixed at 250 pulses per sec per electrode (ppspe), only one stimulation rate was tested with the SPEAK processor. Three stimulation rates (900, 1200, and 1800 ppspe) were tested in the ACE processing conditions. Four stimulation rates (1200, 1800, 2400, and 3600 ppspe) were tested in the CIS processing conditions. Because the number of stimulating electrodes determines the stimulation rate in CIS processors, the number of electrodes was reduced from 12 to 8 to 6 to 4 to achieve stimulation rates of 1200, 1800, 2400, to 3600 pps. Results: Results showed that mean Chinese tone recognition scores with the ACE and CIS strategies were significantly higher than those with the SPEAK strategy. For the ACE strategy, there was no significant difference in performance among the various stimulation rates (for the ACE processing conditions, the stimulation rate was varied while keeping the number of stimulating electrodes constant). For the CIS strategy, there was no significant difference among the various stimulation rates and electrode configurations (for the CIS processing conditions, the stimulation rate was varied by changing the number of stimulating electrodes). There was also a significant correlation between Chinese tone recognition and the recognition of everyday sentences. Conclusions: The latest-generation speech processing strategies were able to provide cochlear implant users with considerable amounts of tonal information. However, Chinese tone recognition was significantly affected by the choice in speech processing strategy. Relatively higher stimulation rates (>900 ppspe) may improve Chinese tone recognition. Furthermore, it may be necessary to develop speech processing strategies to specifically improve tone recognition, which is critical for understanding tonal languages. Previous studies have shown that speech processing strategies have a significant effect on cochlear implant listeners’ speech recognition performance. However, little is known about speech processor strategies’ effects on the recognition of suprasegmental information, e.g., tones in a tonal language. The present experiment evaluated the effects of speech processing strategy on Chinese tone recognition by Nucleus-24 cochlear implant patients. Results showed that mean Chinese tone recognition scores with the ACE and CIS strategies were significantly higher than those with the SPEAK strategy. For the ACE strategy, there was no significant difference in performance among the various stimulation rates. For the CIS strategy, there was no significant difference among the various stimulation rates and electrode configurations. Results suggested that Chinese tone recognition was significantly affected by the choice in speech processing strategy. Relatively higher stimulation rates may improve Chinese tone recognition.