Masking in audiometry; further studies.

Abstract

Interaural attenuation plays an important part in clinical masking tests. Attempts have been made to increase the average figure of 50 db for ordinary, air conduction receivers to higher insulation by using an ear canal insert which greatly reduces the area under the sound.Two types of inserts were used: one, made of plastic and fitted over the earphone, led the tone via a perforated tip into the meatus. The other employed a microphone of hearing-aid type, leading the tone to the ear canal by a plastic tube with soft rubber point. Interaural attenuation was measured by the masking method.The hearing-aid type plastic tube in the meatus was the better of the two, providing 70 db insulation. It proved to be easy to handle and convenient to use.The rules governing the use of masking in audiometry are discussed briefly. For clinical routine use, white noise is preferred to bands of noise.