Spectral Distribution of /s/ and the Frequency Response of Hearing Aids

Abstract

The purpose was to determine a target for the upper frequency limit of a hearing aid that will provide access to the important spectral cues for all the sounds of English.The sibilant /s/ was studied because of its high-frequency content. Repeated tokens of Is/ were recorded from five men and five women before and between the vowels /u/, /a/, and /i/. Using fast Fourier transform analysis, the prominent spectral peak with the lowest frequency was identified and its center frequency determined for each token. This frequency averaged around 4.9 kHz for the /u/ context, 5.6 kHz for the /a/ context, and 6.0 kHz for the /i/ context. There were dramatic differences among talkers, with subject means ranging from 3.2 to 8.4 kHz.The women generated consistently higher frequency Is/ sounds than the men, but there were also large differences within gender groups. These data suggest that the upper frequency limit of a high-fidelity hearing aid should be in the region of 10 kHz. If this cannot be accomplished with direct amplification, an alternative might be the selective use of frequency transposition. (Ear Hear 13 3:150-157)

Production of contrast between sibilant fricatives by children with cochlear implants

“…The spectra of /s/ and /$/ are each characterized by spectral peaks, the spectral peaks of /s/ being typically higher in frequency than the spectral peaks of /$/. The exact spectral shapes of /s/ and /$/ vary across speakers and contexts (Boothroyd and Medwetsky, 1992;Stevens, 2000).…”

Neural Representation of Amplified Speech Sounds

“…For example, many hearing aids have a limited high-frequency response. If the bandwidth of a speech signal extends into higher frequency regions than the hearing aid is capable of processing, critical spectral information will be lost Boothroyd & Medwetsky, 1992;Stelmachowicz, Kopun, Mace, et al, 1995). In the case of /s/, the prominent spectral peak can vary from 2.9 kHz to 8.9 kHz.…”

Effect of Probe Tube Insertion Depth on Spectral Measures of Speech

“…For analog hearing aids, a frequency-gain response was considered adequate if it amplified through 3 kHz. 31 Digital aids have frequency responses that extend to 6 kHz or higher. To evaluate such amplification effects, accurate measurement of high-frequency levels is necessary.…”