Abstract
The phase change of bone-conduction has been measured by two methods. First method is as follows; one listen a bone-conduction tone and an air-conduction tone at the same time. When these tones have the inverse phase to each other and equal intensity, then one can not perceive them. When the position of bone-conduction receiver is displaced, the corresponding phase difference is obtained from the displacement of air-conduction tone source. In the low frequencies of less than about 2000 cps, the vibration of the temple is in the inverse phase to that of the forehead, but this vibration mode is not so clear. Second method is as follows; one listen two bone-conduction tones at the same time. One of the bone-conduction receiver is displaced over the head to find the position of inverse phase. The phase of bone-conduction receiver can be reversed by the turn of switch. Thus the nodal lines of the vibration of head is obtained. In the high frequencies more than about 2000 cps, the nodal lines observed very clearly. This can be explained by the fundamental resonance of skull at about 2000 cps.
