PURPOSE: To evade regulation by the radio law, and to remove the occurrence of a noise due to the mechanical vibration of a wire, etc., in a bone transmission type microphone by converting the vibration of an ear bone into on electric signal by a vibration-electricity conversion element, and further, amplifying it, and transmitting it as a modulated frequency signal by an electricity-sound converting means.

CONSTITUTION: A plug 1 is formed into a cylindrical shape, and is inserted into an external auditory meatus 2. The vibration-electricity converting means 4 supported by an inner case 3 is stored in the plug 1 together with a damper 5. A protruding part 6 is formed at an eccentric position at a part of the inner case 3 so that the vibration-electricity converting means 4 can pick up efficiently the vibration of the ear bone. The vibration of the ear bone converted into the electric signal by this vibration-electricity converting means 4 is amplified to a prescribed level by an amplifier 8 integrated with a signal control means 7, and is amplitude-modulated or frequency-modulated by a modulating means in the signal control means 7. The modulated signal is inputted to the electricity-sound converting means 9, and the modulated sound signal is transmitted as being carried by an ultrasonic wave by an ultrasonic wave generator 10 integrated with it.