Temporary Hearing Threshold Shifts and Cognitive Effects Induced by Ultrasonic Noise Exposure

This study examined the auditory and cognitive effects of occupational ultrasonic noise exposure through controlled laboratory experiments simulating workplace conditions. A group of 20 participants aged 18–35 underwent pure-tone audiometry (PTA) in both standard (1–8 kHz) and extended high-frequency (9–16 kHz) ranges before and after exposure to airborne ultrasound emitted by an ultrasonic cleaner. The exposure was conducted at two sound pressure levels: at the current permissible occupational limit and at a level 5 dB below it. The results demonstrated statistically significant temporary threshold shifts (TTS) in hearing sensitivity (bilaterally) at 8 kHz and 16 kHz only at the higher exposure level, with mean shifts reaching 3.8 dB and 5.8 dB, respectively. No significant hearing threshold changes were observed at the reduced exposure level. Additionally, participants completed a battery of Abilitest cognitive tests during exposure. Comparisons with standardized normative data showed that reaction times were approximately 20% longer in simple response tasks and 13% longer in selective attention tasks, suggesting a potential deviation in cognitive performance associated with ultrasonic noise. These findings support the need to reevaluate current occupational exposure limits and highlight the potential health and performance risks associated with airborne ultrasound.