EARPHONE SYSTEM FOR HUMAN INFANTS
Philip Peltzman, Alan Bass, David Manchester · The Journal of the Acoustical Society of America · 1970
A condenser microphone-driver system has been designed specifically for use as an infant earphone. A simple economical negative feedback amplifier compensates for the distortion of the condenser microphone when used as an earphone. The physical properties and unique advantages of the insert ear tubes present no apparent discomfort to a sleeping or awake infant, afford a measure of sound pressure generated in the ear canal, and permit a wide latitude of head movement.