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Acoustic ground impedance meterA compact, portable instrument was developed to measure the acoustic impedance of the ground, or other surfaces, by direct pressure-volume velocity measurement. A Helmholtz resonator, constructed of heavy-walled stainless steel but open at the bottom, is positioned over the surface having the unknown impedance. The sound source, a cam-driven piston of known stroke and thus known volume velocity, is located in the neck of the resonator. The cam speed is a variable up to a maximum 3600 rpm. The sound pressure at the test surface is measured by means of a microphone flush-mounted in the wall of the chamber. An optical monitor of the piston displacement permits measurement of the phase angle between the volume velocity and the sound pressure, from which the real and imaginary parts of the impedance can be evaluated. Measurements using a 5-lobed cam can be made up to 300 Hz. Detailed design criteria and results on a soil sample are presented. Previously announced in STAR as N82-17476
Document ID
19830056514
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Zuckerwar, A. J.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 11, 2013
Publication Date
June 1, 1983
Publication Information
Publication: Acoustical Society of America, Journal
Volume: 73
ISSN: 0001-4966
Subject Category
Instrumentation And Photography
Accession Number
83A37732
Distribution Limits
Public
Copyright
Other

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