The novel method, which we call the “Optical Wave Microphone (OWM)” technique, is based on a Fraunhofer diffraction effect between a sound wave and a laser beam. The light diffraction technique is an effective sensing method to detect the sound and is flexible for practical uses as it involves only a simple optical lens system. OWM is also very useful to detect the sound wave without disturbing the sound field. This new method can realize high accuracy measurement of slight density change of atmosphere. Moreover, OWM can be used for sound field visualization by computerized tomography (CT) because the ultra-small modulation by the sound field is integrated along the laser beam path.
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