Acoustic Laboratories were established in 1948 by the Australian Department of Health to undertake scientific investigations relating to hearing aids, their application t o the needs of individuals, the effects of noise on man, andlto provide a hearing aid scheme t o sections of the community.The first investigations into ultrasound were undertaken in the early 50's t o study the effects of noise on man. These studies were concerned with the measurement of airborne energy above the audible frequency limit generated by jet aircraft and the possible harm that this energy could cause to humans. This work came to a quick halt when it was found that significant amounts of ultrasonic energy were found only at distances very close t o the aircraft; at these distances the audible and subaudible components of the acoustic energy generated by the engines posed a far greater hazard than did the ultrasonic energy.