Audiometry equipment c. 1970 comprising: delayed side tone autiometer, mk2, by Brenell. Pitch discrimination audiometer, mk2. Beat frequency oscillator by Bruel & Kjaer, Copenhagen. Noise average meter by C.E.L. Recorder/Player by Leevers-Rich. Condenser microphone by Bruel & Kjaer. Electronic voltmeter type 2409 by Bruel & Kjaer. Noise dosimeter type 122 by C.E.L. Microphone amplifier 2601. Level recorder by Bruel & Kjoer Audiometry equipment c. 1970 comprising: delayed side tone autiometer 1970