Effects of frequency and duration of sound stimuli on hearing threshold increments among hearing-impaired individuals in Taiwan

Abstract

This study investigated the effects of hearing type (with or without earphones) and sound stimulus exposure duration (90 s, 105 s, and 120 s) on increments in the hearing threshold with sound stimulation at various frequencies (125 Hz, 1,000 Hz, and 6,000 Hz), using an ascending run, in 48 hearing-impaired individuals. A 2 (hearing type) × 3 (sound stimulus exposure duration) × 3 (frequency of stimulus noise) repeated-measures design and an ascending method of limits was used in the experiment. Increments of the hearing threshold of the participants were analyzed using three-way repeated-measures analysis of variance. We found that the increase in hearing threshold was significant when participants wore earphones than when they did not. The hearing threshold increment was higher when the duration of sound exposure was 120 s and 105 s than when it was 90 s; moreover, the increment in the hearing threshold for a sound exposure duration of 105 s was less than that for 120 s. The frequency of the sound stimulus also affected increments in the hearing threshold: 1000 Hz was associated with a larger hearing threshold increment than were 125 Hz and 6000 Hz; however, there was no difference in the hearing threshold between 125 Hz and 6000 Hz stimuli. Our findings have implications for design of products for the hearing-impaired, for example, the design of card-sensing sounds and siren sounds, which are related to safety issues.