The Relationship of Pitch Discrimination with Segregation of Tonal and Speech Streams for Cochlear Implant Users

Cochlear implant (CI) users often complain about music appreciation and speech recognition in background noise, which depend on segregating sound sources into perceptual streams. The present study examined relationships between frequency and fundamental frequency (F0) discrimination with stream segregation of tonal and speech streams for CI users and peers with no known hearing loss. Frequency and F0 discrimination were measured for 1,000 Hz pure tones and 110 Hz complex tones, respectively. Stream segregation was measured for pure and complex tones using a lead/lag delay detection task. Spondee word identification was measured in competing speech with high levels of informational masking that required listeners to use F0 to segregate speech. The hypotheses were that frequency and F0 discrimination would explain a significant portion of the variance in outcomes for tonal segregation and speech reception. On average, CI users received a large benefit for stream segregation of tonal streams when either the frequency or F0 of the competing stream was shifted relative to the target stream. A linear relationship accounted for 42% of the covariance between measures of stream segregation and complex tone discrimination for CI users. In contrast, such benefits were absent when the F0 of the competing speech was shifted relative to the target speech. The large benefit observed for tonal streams is promising for music listening if it transfers to separating instruments within a song; however, the lack of benefit for speech suggests separate mechanisms, or special requirements, for speech processing.