Effects of local vibration transmitted from ultrasonic devices on vibrotactile perception in the hands of therapists

Nine ultrasonic therapists and nine controls have been studied with regard to vibration perception thresholds within the frequency range of 5–400?Hz. Thresholds on the tip of the index and middle finger for both left and right hand were studied. In contrast to the controls, the therapists had been exposed professionally to local vibration with high frequencies, around 1?MHz, from the handles of ultrasonic transducers used for therapy in medical service. For the therapists, compared with the controls, a reduction of vibration perception was seen. This result supports the suspicion that vibration with high frequencies might have a negative influence on man.