Backscattering measurement method for sound field using pulsed laser

This paper presents a sound field measurement method utilizing light scattering. Since the intensity of scattered light is proportional to density of scatterers, the fluctuation of air density, which is corresponding to sound pressure, can be acquired by observing the light scattered by air particles. The light scattered in the sound field, therefore, includes the sound information in its intensity. The measurement apparatus is composed of a pulsed laser, a telescope and a photo-multiplier tube (PMT). The backscattered light is collected by the telescope and detected by the PMT. Using the pulsed laser and detecting the backscattered light enable to acquire sound quantity of an arbitrary point on optical light path by controlling signal acquisition timing. The results of the fundamental experiments confirm a validity of this method.