TECHNIQUES FOR THE MEASUREMENT OF ACOUSTIC IMPEDANCE OF ASPHALT
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.
- Prepared for Environmental Protection Agency, Washington, DC. Office of Noise Abatement and Control.
National Engineering Laboratory (NBS)Acoustical Engineering Division
Washington, DC USA
Environmental Protection AgencyOffice of Noise Abatement and Control, 1921 Jeff Davis Hwy
Arlington, VA USA 20460
- Mansbach, P A
- Holmer, C I
- Publication Date: 1978-10
- Pagination: 94 p.
- TRT Terms: Accuracy; Acoustic impedance; Acoustic measuring instruments; Acoustics; Asphalt pavements; Costs; Flexible pavements; Measuring instruments; Noise; Sound level meters; Temperature gradients; Transportation; Wind
- Uncontrolled Terms: Comparative analysis; Transportation noise
- Old TRIS Terms: Acoustic measurement; Sound analyzers
- Subject Areas: Pavements; Transportation (General);
- Accession Number: 00190825
- Record Type: Publication
- Source Agency: National Technical Information Service
- Report/Paper Numbers: NBSIR-78-1541 Final Rpt.
- Files: TRIS
- Created Date: Mar 28 1979 12:00AM