Development of a Large-Scale Microphone Array for Aircraft Jet Plume Noise Source Characterization 2011-01-1733

Military jet aircraft expose both ground maintenance personnel and the community to high levels of noise. The U.S. Department of Defense is funding research to develop advanced modeling tools for noise reduction techniques and community noise exposure. A large-scale microphone array for portable near-field acoustic holography (NAH) and data acquisition system was created for this purpose.

The system was designed for measuring high-amplitude jet noise from current and next-generation military aircraft to provide model refinement and benchmarking, evaluate performance of noise control devices, and predict ground maintenance personnel and community noise exposure. The acoustical instrumentation system was designed to be easy to use with scalable data processing as the primary focus. The data acquisition system allowed up to 152 channels simultaneously sampled at a rate of 96 kHz.

The application of NAH processing to the characterization of a full-scale jet plume environment and the development of an appropriate measurement array poses several technical and logistical challenges. Accurate characterization of the near field of a military jet aircraft requires the ability to record sound pressure levels up to 170 dB and frequencies from 5 Hz to 30 kHz. In addition, measurements needed to be made along the entire length of the plume. The NAH system needs to be semi-portable because of the limited number of locations where military jets can perform static high-power engine run-ups. The data collected demonstrated that this system can be used to obtain near-field acoustic data of jet plumes from high-power aircraft.