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A method for reducing ground reflection effects from acoustic measurementsThe method involved placing foam blocks on the ground between sound source and receiver in an approximation of the wedges in an anechoic chamber. The tests were performed out of doors as a function of the receiver height and source-receiver separation distance. The spacing between blocks and the extent of ground covered were varied to estimate the optimum placement and minimum amount of foam treatment needed. Base-line tests without foam were also performed. It was found that the foam treatment reduced the amplitude of the peaks and valleys in the sound pressure spectra substantially. The foam was least effective at low frequency, especially for the low receiver height and for large source-receiver distances. Results from the base-line tests were compared with theoretically predicted results. These base-line test results were in reasonable agreement with those from theory.
Document ID
19720012091
Acquisition Source
Legacy CDMS
Document Type
Other - NASA Technical Note (TN)
Authors
Noerager, J. A. (NASA Lewis Research Center Cleveland, OH, United States)
Rice, E. J. (NASA Lewis Research Center Cleveland, OH, United States)
Feiler, C. E. (NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
September 2, 2013
Publication Date
March 1, 1972
Subject Category
Physics, General
Report/Patent Number
NASA-TN-D-6666
E-6573
Accession Number
72N19741
Funding Number(s)
PROJECT: RTOP 132-80
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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