Characteristics of Multiple-reflection Laser Microphone for Spherical Sound wave Detection

抄録

The laser microphone with self-coupling effect of laser diode has the single-reflection laser beam, instead of the membranes. Because the laser beam works as the detection parts of the laser microphone, it has the wide and flat frequency response and the detectability under the high electromagnetic field. Single-reflection laser microphones are unable to detect spherical sound waves from a point source because of their low spatial resolution. In order to solve this problem, a multiple-reflection laser microphone employing a pair of mirrors has been developed. It was found that the frequency response of the multiple-reflection laser microphone is affected by the size of the detection area. The sensitivity is proportional to the number of reflections, which is seven times higher than the single-reflection laser microphone of the same spatial resolution. The multiple-reflection laser microphone can detect the spherical sound wave as same as the commercial 1/4 inch diameter condenser microphone.