Measurement of Exterior Noise Produced by Aircraft Auxiliary Power Units (APUs) and Associated Equipment During Ground Operation
Test procedures are described for measuring noise at specific locations (passenger and cargo doors, and servicing positions) and for conducting general noise surveys around aircraft.
Requirements are identified with respect to instrumentation; acoustic and atmospheric environment; data acquisition, reduction and presentation, and such other information as is needed for reporting the results.
Recommended procedures involve recording data on magnetic tape for subsequent processing. The use of tape-recorder/time-integrating analyzer systems avoids the need to average by eye the variations associated with manual readings from sound level meters and octave band analyzers and, therefore, yields more accurate results.
This document makes no provision for predicting APU noise from basic engine characteristics, nor for measuring noise of more than one aircraft operating at the same time.
No attempt is made to suggest acceptable levels of noise or suitable subjective criteria for judging acceptability.