抄録
An Optical Wave Microphone System (O.W.M.S) is a new sound measuring device which need not install a device directly at measuring point like a condenser microphone and need not mix particulate materials like Leaser Doppler Velocimetry. Therefore O.W.M.S can measure sound without disturbing sound fields. Study on the reduction of jet noise has already been carried out, and the Perforated Tube could decrease jet noise at high pressures. However at low pressure peculiar sound noises were detected. Now this paper report our study of investigation concerning directional characteristics of jet noise of perforated tube in the field around the jet nozzle by using new measuring method of an Optical Wave Microphone System.
