Abstract: A digital electro-acoustic transducer for improving the speech quality of sound under noisy circumstances is disclosed. A plurality of sound generating units A constituted by electrostatic electro-acoustic transducers (condenser earphones) and a sound receiving unit B constituted by an electrostatic acousto-electric transducer (condenser microphone) are disposed in a cavity of a soundproof housing. The units A are provided in a feedback loop and an output level of the unit B is adjusted by an preamplifier. An output of the preamplifier is sampled by a sample-and-hold circuit and an output thereof is delta-modulated by a delta modulation circuit. The number of pulses produced by the circuit is subjected to arithmetic operation in an arithmetic circuit to produce a drive signal for the units A. Vibration of a vibration film of the unit B is detected and arithmetical control is made to be always maintained to zero.
Type:
Grant
Filed:
May 13, 1999
Date of Patent:
September 10, 2002
Assignees:
Matsushita Electric Industrial Co., Ltd.