The effects of two different speech-coding strategies on voice fundamental frequency control in deafened adults

Control of voice fundamental frequency (Fx) during reading of a standard passage was assessed for four profoundly deafened adults receiving auditory feedback in one of two conditions: (i) with an extended low-frequency response amplifying aid; (ii) with the SiVo aid, which provided only Fx information. A third condition, where the subjects were unaided, was also included. For each feedback condition, quantitative analyses of laryngograph recordings were used to provide measures of Fx mode, 90% Fx range and the regularity of vocal fold vibration. In baseline unaided recordings, three subjects (S1, S2 and S4) showed some aspects of Fx control outside the normal range, while the other (S3) had appropriate Fx control. In the three subjects with impaired control, simplified Fx feedback led to better control than feedback from amplified speech. In two of these subjects, these differences were statistically significant. S3, who showed unimpaired Fx control, did not show any changes in Fx control under the different feedback conditions. Although the patterns of data were different in the individual subjects, simplified Fx feedback led to either improved or unimpaired control of Fx relative to speech feedback or to not feedback. These findings have important implications for speech-processing strategies implemented in hearing aids and cochlear implants, where the effects of different speech-coding strategies on production have been largely ignored.