Laser Sensor for Acoustic Measurement in Wind Tunnels

We propose a system that utilizes a laser to measure the acoustic radiation emitted by test vehicles in a wind tunnel.. Its immediate advantages are: no need for struts to support microphones, good discrimination against wind tunnel reverberation, no microphone wind/flow noise to degrade sensor SNR nor cause downstream turbulence to interfere with the item under test. The technique is based on exploiting natural particles in the air. By remotely measuring the motion of the particles the laser measures the acoustic field radiated by the test article. In effect, the laser creates a virtual microphone positioned at the location of the laser probe volume, and being massless, there is no wind/flow noise. Multiple probe volumes can be arranged along the laser beam to create a one-dimensional acoustic array. Multiple laser beams can be used to create a two-dimensional array. The laser beam(s) can be steered to gather data at most angles of interest with respect to the test article.