An experimental Investigation was made of the effects of speech peak clipping, pre-emphasls, de-emphasis and automatic gain control as might be applied in the microphone amplifier of an interphone system for Army aircraft. The system con¬sidered makes use of M-33/AIC microphones, H-70/AIC headsets and listening amplifiers of Intercommunication Set AN/AIC-12(XC-1). Noise levels up to 120 db are considered. Articulation tests were conducted to determine the effects of variations in these parameters. The microphone output voltages for twenty-four talkers under several conditions of noise and sidetone were measured.nIt was concluded that in such a system no pre-emphasls or de-emphasis should be used, 6 to 12 db of peak clipping should be provided, under control of the listener, and that automatic gain control should be provided in the microphone amplifier.
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