Assessment of short-term exposure to an ultrasonic rodent repellent device.

The objectives of the present study were to investigate the acoustical properties of the very high frequencies and/or ultrasound signals produced by a repellent device and to investigate potential adverse factors as a result of short-term exposure to these signals. Potential adverse effects were evaluated perceptually with 25 young and 25 middle-aged persons, all with normal hearing thresholds, in a quiet room using different outcome measures, including a 15-item survey presented before and immediately after each condition. Spectral analyses showed that, besides emitting frequency modulated sounds in the expected frequency ranges, a faint but audible sound in the 4-5 kHz range was present. On average, a relatively short exposure to the sound produced by a repellent device did not lead to significant adverse effects. Yet, when the signal was perceived, as it was frequently for the younger population at the two lower frequencies settings (12-14 kHz, 25-25 kHz) and with 2 sources emitting, it was considered to be disturbing by several participants. Given the increasing usage of ultrasonic devices as well as the much longer exposure of high frequency and ultrasound in domestic usage, careful consideration and better guidelines are required, especially for those who are most sensitive to sound.