Accession Number : AD0493887

Title :   MEASUREMENT OF ACOUSTIC IMPEDANCE.

Descriptive Note : Technical memo.,

Corporate Author : HARVARD UNIV CAMBRIDGE MA ACOUSTICS RESEARCH LAB

Personal Author(s) : Mawardi, Osman K.

Report Date : 25 MAY 1949

Pagination or Media Count : 79

Abstract : In this technical memorandum a method is described to measure the acoustic impedance of a sample of material forming one boundary of a shallow cylindrical cavity, by determining the sound pressure produced when a known volume current is injected into the cavity from a high-impedance source. The volume current is effectively determined by observing the pressure when the cavity is rigidly terminated. The use of a ring source suppresses the first radial mode of the cavity and extends the frequency limit set by uniformity of pressure by at least an octave. Secondary effects due to the finite impedance of the source and microphone and heat losses at the walls have been evaluated. The method appears to be simple, rapid, and precise. (Author)

Descriptors :   *MEASURING INSTRUMENTS), (*ACOUSTIC IMPEDANCE, CYLINDRICAL BODIES, MEASUREMENT, PRESSURE, COMPOSITION BOARD, SOUND TRANSMISSION, INSTRUMENTATION, RINGS, HEAT TRANSFER, INTENSITY, MICROPHONES, RESONANCE, RESONANT FREQUENCY.

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE