Authors: Susan Black¹, Matt Davis¹, Abbie Bradshaw¹
¹University of Cambridge
Background: Cochlear implants (CIs) provide deaf individuals with access not only to external speech, but also auditory feedback from their own voice during production. This experiment investigated whether typical hearing participants can use CI simulated speech feedback for perceptual learning and sensorimotor control of speech during production. Spectral degradation for CI simulation was achieved via noise vocoding.
Methods: 32 participants took part in the experiment. First, participants were tested on their recognition of noise vocoded sentences before and after a training task; either perception training where participants listened to noise vocoded sentences while reading matching text, or production training where participants read aloud sentences whilst hearing their own voice noise-vocoded in real-time. Both groups then read aloud sentences while formant shifts were applied to their real-time noise-vocoded speech auditory feedback (direction of shift manipulated between-groups). Sensorimotor learning requires changing produced formants in the opposite direction to the shift applied.
Results: Both perception and production training resulted in significant improvements in recognition; training type however did not affect the magnitude of this improvement. Sensorimotor learning was not significant at the group level in response to the formant perturbations; however, exploratory analyses suggested that participants who first underwent the production training task (and thus had more experience of the noise vocoded feedback) showed greater adaptation than participants in the perception training group.
Conclusions: Equivalent recognition performance after perception and production training suggests that sensory suppression during speech production does not prevent perceptual learning of degraded speech. However, successful perceptual learning for noise-vocoded speech is not sufficient for successful sensorimotor learning with noise-vocoded speech auditory feedback.
