No difference between the two stimulus conditions was seen in performance on the attention task or on average GSRs for either group.įor more than 70 years there have been reports of adverse symptoms resulting from exposure to very high frequency sound (VHFS 11.2–17.8 kHz) and ultrasound (US > 17.8 kHz, for reasons discussed by Leighton, 2017 21. In the symptomatic group only, difficulty concentrating and annoyance were also rated higher in the VHFS/US than the reference condition. In both groups, overall discomfort ratings were higher in the VHFS/US condition than the reference condition. Prior to exposure, participants were assigned either to a symptomatic or an asymptomatic group, based on their prior history of symptoms that they attributed to VHFS/US. The VHFS/US and reference stimuli were presented 4 times, each time for 3 min, during which participants performed a sustained attention task, rated their symptom severity, and had their galvanic skin response (GSR) measured to assess their level of anxiety. To do this, participants were exposed to VHFS/US (at frequencies between 13.5 and 20 kHz and sound pressure levels between 82 and 92 dB) and to a 1 kHz reference stimulus, both at 25 dB above their hearing threshold. This study aimed to establish whether these symptoms are experienced under controlled laboratory conditions and are specific to VHFS/US. Various adverse symptoms resulting from exposure to very high-frequency sound (VHFS) and ultrasound (US) have previously been reported.
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