PURPOSE: To obtain good characteristics both in sound pressure and sound quality by making the diaphragm breathing spherical form.

CONSTITUTION: A film diaphragm 12 is a spherical body called a breathing sphere. It changes its radius and axial length that is, expands and contracts, and emits nearly ideal spherical wave. A driving section 13 is a member to drive the diaphragm 12. A frame 14 supports directly the diaphragm 12 and driving section 13 when inserted to the ears and prevents attenuation of sound caused by direct contact of the diaphragm with external auditory miatus. When a headphone of this structure is inserted into the external auditory miatus, sound energy can be transmitted effectively even by small output. As leak resistance is not caused theoretically, drop of sound pressure of low frequency range can be avoided.