OBJECT SOUND DETECTION METHOD AND ITS DEVICE

PROBLEM TO BE SOLVED: To provide a detection device for sound radiated from an acoustic radiation face of a measuring object in the general use state or in the operation state of the measuring object. SOLUTION: This object sound detection device for detecting a sound in an audio-frequency range radiated from the acoustic radiation face 12 of a vibrating object 13 is equipped with a half-reflecting thin film mirror 5 for detecting a sound pressure near the acoustic radiation face 12, a laser oscillator 2 for irradiating wavelength sweep laser light toward the acoustic radiation face 12 and the half-reflecting thin film mirror 5, a beam splitter and a total-reflecting mirror 4 for allowing reflected light from the acoustic radiation face 12 and the half-reflecting thin film mirror 5 to interfere with the wavelength sweep laser light, a laser photodetector 6 for detecting simultaneously the interference intensity between the reflected light from the acoustic radiation face 12 and the half-reflecting thin film mirror 5 and the wavelength sweep laser light, frequency-voltage converters 7, 8 for converting a frequency change by a Doppler shift into vibration speeds of the acoustic radiation face 12 and the half-reflecting thin film mirror 5, and a cross spectrum operation part 11 for determining a cross spectrum of the vibration speeds of the acoustic radiation face 12 and the half-reflecting thin film mirror 5. COPYRIGHT: (C)2005,JPO&NCIPI