Record Display for the EPA National Library Catalog


OLS Field Name OLS Field Data
Main Title Techniques for the Measurement of Acoustic Impedance of Asphalt.
Author Mansbach, Peter A. ; Holmer, Curtis I. ;
CORP Author National Engineering Lab. (NBS), Washington, DC. Acoustical Engineering Div. ;Environmental Protection Agency, Washington, DC. Office of Noise Abatement and Control.
Year Published 1978
Report Number NBSIR-78-1541; NBS-2004457;
Stock Number PB-287 936
Additional Subjects Flexible pavements ; Acoustic impedence ; Acoustic measuring instruments ; Sound analyzers ; Wind ; Temperature gradients ; Transportation noise ; Noise pollution ; Truck noise
Library Call Number Additional Info Location Last
NTIS  PB-287 936 Most EPA libraries have a fiche copy filed under the call number shown. Check with individual libraries about paper copy. NTIS 06/23/1988
Collation 94p
Five techniques were used in an attempt to measure the very high acoustic impedance of an asphalt surface. These techniques are: Impedance Tube, Pure-Tone Traverse, Pulse-Echo, Broad-Band Cross-Correlation, and Direct Accelerometer Measurement. These techniques are described and evaluated in some detail, and the results of the measurements are presented. Of the five techniques, the broad-band cross-correlation proved to be the most effective, and also is capable of even further improvement. The value of the specific acoustic admittance of the sealed asphalt surface obtained with this technique is .007. The effects of wind and temperature gradients on ray propagation are derived theoretically, as well as spherical wavefront corrections to plane-wave reflection. These refinements are necessary to realize the full potential of the broad-band measurement technique. Effects of the finite test surface impedance on source emission measurements are discussed. Measurement uncertainties of the order of 1-2 dB due to surface impedance are considered likely.