| Like a police officer might find
fugitives hiding in the dark using night vision goggles
which detect the thermal infrared light from their bodies,
engineers can use phased array systems to pinpoint noise
sources.
In a phased array system, microphones are placed in
a 1D, 2D or 3D arrangement and when sound measurements
from these microphones are properly processed, noise
sources can be pinpointed.
NASA Glenn has developed a 16-microphone linear array
and an 80-microphone cage array which have been used
to find the noisy spots in the plumes of different
nozzle concepts tested in the rigs of the AeroAcoustic
Propulsion Lab.
A 63-microphone spiral-ring array has also been used
to hunt down fan noise sources in tests in the 9’ x
15’ Low Speed Wind Tunnel.
NASA engineers have even stepped beyond the gates
of the Glenn Research Center, and applied their expertise
to identify noise sources in static engine tests for
General Electric and Honeywell Engines and Systems
using linear, 2D, and cage array systems.
Phased array data can be used to target noise sources,
giving engineers clues to help them apply treatment
where it is most needed.
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