The present invention relates to a displacement sensor and, in particular, relates to such a device which senses the displacement or vibration of a living body. The present invention is applicable to a stethoscope for medical purposes, and mechanocardiogram.
Conventionally, an acoustic stethoscope has been used for diagnosing a living body. A prior stethoscope places a diaphragm on a surface of a living body, and the vibration of the diaphragm is listened to by a doctor through a stethoscope tube.
Therefore, a prior stethoscope has the disadvantage that only a single doctor can listen to the sound of vibration of heart valves of a living body, but it can not be listened to by a plurality of persons. Further, a prior stethoscope has the disadvantage that a doctor cannot listen to the sound of a heart beat due to a low frequency less than 20 Hz and the output of the stethoscope can not be recorded.
On the other hand, a prior electrocardiogram records pulsation or drive electrical signals of a heart, but it does not record an actual mechanical movement of a heart. Therefore, if there is something wrong with a heart such as valve desease and arteriosclerosis, it could not be detected by a prior electrocardiogram. Conventional mechanocardiograph sensors for detection of heart movement are difficult to treat due to their bad treatability.