Analysis of temporary threshold shifts in hearing after exposure to ultrasonic noise

This study presents preliminary results of evaluating the impact of ultrasonic noise on the auditory system, utilizing the most commonly employed method - pure-tone audiometry (PTA) for determining hearing thresholds. The research aimed to investigate the temporary threshold shifts (TTS) resulting from exposure to ultrasonic noise. Participants were exposed to ultrasonic noise within the frequency range of 16 kHz to 40 kHz, corresponding to the lower ultrasonic band typically emitted by industrial devices. The temporary threshold shift measurements, however, were conducted within the audible frequency range. Hearing thresholds were measured before and after exposure, within the standard range of 1 to 8 kHz and the extended range of 9 to 16 kHz. Twenty participants were exposed to two types of ultrasonic signals representing typical industrial sources - an ultrasonic cleaner and an ultrasonic welder. The analysis of results revealed statistically significant differences in hearing thresholds (both sides) for 8 kHz and 16 kHz after exposure to ultrasonic noise, regardless of the type of ultrasonic noise source. The average differences were 3.8 dB for 8 kHz and 5.8 dB for 16 kHz in the case of the ultrasonic cleaner, and 2 dB for 8 kHz and 3.5 dB for 16 kHz in the case of the ultrasonic welder. Despite smaller differences before and after exposure with the ultrasonic welder, the analysis did not show statistically significant differences regarding the influence of the type of noise source.