Transmitter-receiver having ear-piece type acoustic transducing part

Abstract

Ear-piece type acoustic transducing part is provided with a bone-conducted sound pickup microphone for picking up a bone-conducted sound, a directional microphone for picking up an air-conducted sound and an electro-acoustic transducer for transducing a received speech signal to a received speech sound. A transmitting-receiving circuit connected to the acoustic transducing part includes: a low-pass filter which permits the passage therethrough of low-frequency components in a bone-conducted sound signal from the bone-conducted sound pickup microphone; a high-pass filter which permits the passage therethrough of high-frequency components in an air-conducted sound signal from the directional microphone; first and second variable loss circuits which impart losses to the outputs from the low-pass filter and the high-pass filter, respectively; a comparison/control circuit which compares the output levels of the low-pass filter and the high-pass filter with predetermined first and second reference levels, respectively, and based on the results of comparison, controls losses that are set in the first and second variable loss circuits; and a combining circuit which combines the outputs from the first and second variable loss circuits into a speech sending signal.