Further experimental studies on the transfer-function technique for impedance tube measurements

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TypeArticle
Journal titleJournal of the Acoustical Society of America
ISSN0001-4966
Volume83
Issue6
Pages225560; # of pages: 2196
Subjectacoustical impedance; complex reflection coefficients; single-frequency excitation; lock- in amplifier; data analysis; two-microphone transfer function technique limitation; fixed vs. varied microphone positions; astm e 1050-86 standard; standing-wave pattern minimum pressure point; one- microphone sequential sampling; standing wave ratio method; Acoustics; impédance acoustique
AbstractMore refined measurements of the complex reflection coefficients using single-frequency excitation and a lock-in amplifier for data analysis have revealed a limitation in the two-microphone transfer function technique for impedance tube measurements. A fixed choice of microphone positions for all frequencies as suggested by the current standard ASTM E1050-86 will compromise the accuracy of measurements. For accurate measurements, one of the microphone positions has to be close to a minimum pressure point of the standing- wave pattern, preferably the first minimum point. The choice of the other microphone position does not seem to be critical as long as the separation of the two positions is not close to a half-wavelength. The procedure employed in this study uses sequential sampling with one microphone instead of simultaneous sampling with two microphones. It presents a technique that is better than the existing standard methods for impedance tube measurements.
Publication date
LanguageEnglish
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedYes
IdentifierIRC-P-1561
NRC number29414
2200
NPARC number20373958
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Record identifier6540a731-dcca-4bd1-b829-041e62f89874
Record created2012-07-23
Record modified2016-05-09
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