The present invention relates to a sound detector or sound collecting device for detecting blood vessel sounds or vascular sounds by means of a microphone to automatically measure the blood pressure, more particularly, to an improved and unique sound detector to be insertable in a manschette, for use in an automatic sphygmomanometer, provided with a hollow space enveloped by a flexible filmy inner side wall and a rather flexible but less thin outer side shell having an elongated rib integrally formed therewith and a highly sensitive condenser microphone housed in a case connected to the hollow space through a passage for outputting sounds. The present invention has further greatly contributed to the art of this line by providing a few novel modifications such as an arcuate form sound detector for better adaptation on the human body and disposing of a fine aperture in the hollow space for conspicuously reducing the noise collection while measuring.
A blood pressure measuring method by pumping pressurized air into a manschette (an elongated belt like air bag wound on an upper arm of a patient) to raise the air pressure to a certain value once and then gradually lowering it for palpating or ausculating the pulsation at an artery was popular in the past. In recent years a blood measuring device (called an automatic sphygmomanometer), wherein systolic and diastolic pressure are electrically measured (an average blood pressure or pulsation is also measured, if necessary) and digitally indicated by means of vascular sound detection with a microphone, has been developed and put in practice. This sphygmomanometer has largely improved the blood pressure measuring as regards an elimination of individual differences depending on the examiner's skill and a reduction of measuring errors; it still can not be said, however, to be free of some disadvantages. In this conventional instrument a sound detecting method by directly contacting the sound detector including a ceramic microphone or dynamic microphone on a body portion of a patient relatively close to an artery has been generally adopted. Principal inconveniences accompanied thereby are numerated as follows: it has to be properly placed in close contact with the human body (e.g. over an artery of the upper arm), but because it is housed in a substantially flat metalic case (20-25mm in diameter) placement as often difficult in close contact to a human body especially for thin or slender patients or infants; and microphones of this sort are changeable in output level in a low frequency band less than 100 Hz as can be seen in FIG. 2.
A primary object of this invention is to provide a novel sound detector for eliminating the disadvantages inevitable in conventional instruments. The gist of this invention resides in that the sound detector has a hollow unitary space, rather flexible as a whole, having a longitudinal rib disposed therein to maintain the hollow space as it is regardless of some outer pressure, and that it is provided with a highly sensitive condenser microphone housed in a case with the sound collecting portion thereof being disposed to the hollow space.
Another important object of this invention is to provide a novel sound detector to be insertable in the manschette of an automatic sphygmomanometer, wherein the hollow unitary space is of a concave shell for still easier contact on the human body, with the inside surface being made of a thin flexible film and the outside surface being made of a thicker and rather rigid material, and the unitary hollow space is communicated with the outside atmosphere through a fine aperture for greatly reducing the disturbing noise simultaneously picked up.