Simultaneous two-way communication apparatus using ear microphone

The apparatus eliminates howls to permit a received sound to increase in sound volume to enable the apparatus to be used in high-noise areas, and comprises: a transceived sound volume control circuit 10 for controlling in sound volume a transceived sound, the circuit 10 being interposed between: an ear microphone 1 containing a microphone 4 and a speaker 5; and, a communication system 20 such as PHS. The circuit 10 comprises: a communication switching means 16 for performing a switching operation in communications; high-frequency-signal cutting means 17, 19, which attenuate a received sound signal in a transmission mode and then cut a high-frequency component of the signal; and, a transmitted-sound-signal attenuating means 15 for attenuating a transmitted-sound signal in a reception mode. The apparatus comprises a means 14 for cutting energy in the vicinity of a resonance point of the microphone 4, and a means 12 for detecting energy in the vicinity of the first formant of a sound to prevent the switching operation from being initiated due to extraneous noises.