Physiological Noise Generated under Earphone Cushions
W. J. Brogden, George Armitage Miller · The Journal of the Acoustical Society of America · 1947
Listeners were required to match the quality and intensity of a low frequency ambient noise to the quality and intensity of the noise which they heard when they held earphones over both ears. A sound-pressure of 55 or 60 db of rumbling, low frequency noise can be generated by the tremor of the tonic contractions of hand and arm muscles.