Objective: To evaluate Mandarin-speaking cochlear implant patients' understanding of telephone speech.
Design: Telephone speech was simulated by band-limiting broadband speech stimuli (300-3200 Hz) and adding Gaussian noise (35 dB signal-to-noise ratio). Recognition of multitalker vowels, consonants, voice gender, and Chinese tones was measured for both simulated telephone speech and broadband speech in fifteen Mandarin-speaking cochlear implant patients.
Results: Results showed no significant difference in Chinese tone recognition scores between broadband and telephone speech. However, mean recognition scores for vowels, consonants and voice gender were significantly lower with telephone speech. The effect of the limited telephone bandwidth on speech recognition was highly variable among subjects. Some subjects were more sensitive to high-frequency speech cues, resulting in a significant drop in performance with band-limited telephone speech, while other subjects were less sensitive to high-frequency speech cues, resulting in similar performance between broadband and band-limited telephone speech.
Conclusions: These results suggest that the limited bandwidth negatively affects cochlear implant patients' understanding of telephone speech. Because the effect of band-limited speech was highly variable among subjects, the results also suggest that the contribution of high frequency information to speech recognition may vary significantly among cochlear implant patients. For patients who receive little benefit from high-frequency speech cues, speech processor adjustments may be necessary to access the additional cues provided in broadband speech.