Acoustic simulations of combined electric and acoustic hearing (EAS).
OBJECTIVE
Our aim was to explore the consequences for speech understanding of leaving a gap in frequency between a region of acoustic hearing and a region stimulated electrically. Our studies were conducted with normal-hearing listeners, using an acoustic simulation of combined electric and acoustic (EAS) stimulation.


METHODS
Simulations of EAS were created by low-pass filtering speech at 0.5 kHz (90 dB octave roll-off) and adding amplitude-modulated sine waves at higher frequencies. The gap in frequency between acoustic and simulated electric hearing was varied over the range 0.5 kHz to 3.2 kHz. Stimuli included sentences in quiet, sentences in noise, and consonants and vowels. Three experiments were conducted with sample sizes of 12 listeners.


RESULTS
Scores were highest in conditions that minimized the frequency gap between acoustic and electric stimulation. In quiet, vowels and consonant place of articulation showed the most sensitivity to the frequency gap. In noise, scores in the simulated EAS condition were higher than the sum of the scores from the acoustic-only and simulated electric-only conditions.


CONCLUSIONS
Our results suggest that both deep and shallow insertions of electrodes could improve the speech understanding abilities of patients with residual hearing to 500 Hz. However, performance levels will be maximized if the gap between acoustic and electric stimulation is minimized.
Dorman
Michael F
MF
Department of Speech and Hearing Science, Arizona State University, Tempe, Arizona 85287-0102, USA.
Spahr
Anthony J
AJ
Loizou
Philipos C
PC
Dana
Cindy J
CJ
Schmidt
Jennifer S
JS
D000161:Acoustic Stimulation / Q000379:methods*; D000704:Analysis of Variance; D004007:Dichotic Listening Tests; D006801:Humans; D013061:Speech Acoustics; D013067:Speech Perception / Q000502:physiology*; D013647:Task Performance and Analysis