Short term influence of hearing aids on the spectral structure of the sustained [a]

摘要

In this paper, the authors investigate the short-term influence of wearing conventional hearing aids (HA) on the spectrum of the sustained vowel [a]. 80 hearing impaired subjects with a binaural HA were included in the study. Their hearing losses were higher than 50 dB SPL above 500 Hz. Tne subjects were divided into two paired groups. The first group was recorded first without, then with, and finally without hearing aids. The second group was recorded without, then without, and finally with hearing aids. Two kinds of comparison were made between the two groups: ( 1) the comparison of the two first recordings of the groups gave indications on the influence of fitting HA, and (2) the comparison of the last two recordings of the groups tested the difference of fitting vs, removing HA. The acoustical material was a sustained [a] studied globally and in three segments (beginning, middle and end). The vowel spectrum was studied from 0 to 8 kHz. Each frequency band was 500 Hz wide. Results showed a significant modification of the distribution of the energy of vowels in the ranges 0 to 500 Hz, and 1000-2000 Hz. Fitting HA increased the energy percentage in the 0-500Hz band and decreased this percentage in the 1 kHz-2 kHz band. Frequency bands above 2 kHz did not show any systematic significant modification. Removing HA produced the opposite effect. Consequently, this study suggests that (1) there is a short term influence of fitting an hearing aid on voice production, (2) this influence is a redistribution of the energy in favor of the lowest frequencies. [References: 25]