Pitch perception, Modified Sine Wave speech, and Cochlear Implants

Havi Pham, Katrien Vermeire & Jonathan Nissenbaum

CI, or cochlear implants, are surgically implanted neuroprosthesis that provide improved speech and understanding for the hearing impaired individuals. However, current CI technology is still unable to make up for a user’s pitch perception, a psychological phenomenon usually correlated to the fundamental frequency and harmonic structure of a soundwave. Because the mechanisms for understanding pitch perception are still unclear, the lack of pitch intelligibility in CI-users is greatly affected. However new theories within psychoacoustic research propose a “dominance region,” a specific area of audible frequencies ranging from 300 hertz to 1k hertz that play a significant role in the creation of pitch cues. This region falls within the f1, the lowest frequency region of a speech signal. The purpose of this pilot study aims to argue that modified SWS may create a more distinct interpretation of pitch for listeners. If pitch perception in cochlear implants is caused by a signal in noise problem, coding speech through the first format with a sparse cue for pitch could help cochlear implants focus better on pitch changes within the speech signal. Using modified sine wave speech to replicate normal speech through the main formats of a speech this helps focusing on information found in the dominance region (300 hz – 1k hz) in the first formant of the speech signal. This specified space for pitch perhaps can manipulate a cue for pitch.The methods of this study include the use of modified sine wave speech, used to conduct this experiment are eight sentences with pitch focus in the following conditions: question and answer congruence, focusing adverbs, and and reasons and counterfactuals. The stimuli will be a modified SWS, sine wave speech sentences with a f1 created with frequencies within the dominance region to replicate pitch cues. Participants include a group of 20 normal hearing native English speakers between the ages of 18 to 42. Conducted via an online experiment, through Google Forms, participants were given a set of 14 listening tasks based on the created stimuli. The results of this pilot study are still being collected. However, if the results of the study match the expected results of the study, then this can have strong implications for the continuation of this study of pitch perception in cochlear implant users.