Provides for five types of audiometers according to the type of test signal they generate, i.e. pure tone or speech or both, and according to the mode of operation or to their complexity or the range of functions they test, e.g. diagnostic, screen, free-field. Includes testing of hearing by means of air conduction earphones and bone-conduction vibrators using pure tones of specified frequencies and sound pressure level ranges, and also by means of speech signals. Specifications are given for the masking sounds required for standard tests of audiological function. Manual and automatic recording types of audiometers are included.