A sound detecting mechanism capable of forming a diaphragm and a back electrode on a substrate by a simple process includes acoustic holes corresponding to perforations formed on a front surface of a substrate. The slides may have limit stops that are transversely offset with respect to one another. When a machining head moves along an X axis, the reflector-mirror is moved along a U axis parallel to the X axis to keep optical path length constant. The device can select or weight the antennas based upon the position of the device when being held by a user.