Several propagation phenomena which cause variability in standard procedures for noise testing of vehicles are discussed. Attenuation due to interference between direct and ground-reflected waves is considered, as well as the effect of atmospheric turbulence along the propagation path of the noise. The resulting inhomogeneity may be due to natural phenomena or may be induced by the wake of a vehicle. The effects of refraction by the thermal boundary layer close to the ground are analyzed. Acoustic mirages (and shadow zones) are mentioned. It is pointed out that the mirage effect throws considerable doubt on existing measurements of tire noise, where the noise source is presumably very close to the ground.

  • Supplemental Notes:
    • Also published in HS-029 192 (SAE-SP-456), "Vehicle Noise Regulation and Reduction," Warrendale, Pennsylvania, 1980 pp 13-9. Presented at SAE Congress and Exposition, Detroit, 25-29 February 1980.
  • Corporate Authors:

    Society of Automotive Engineers (SAE)

    400 Commonwealth Drive
    Warrendale, PA  United States  15096
  • Authors:
    • Piercy, J E
    • Embleton, TFW
  • Publication Date: 1980

Media Info

  • Features: References;
  • Pagination: 7 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00386640
  • Record Type: Publication
  • Source Agency: National Highway Traffic Safety Administration
  • Report/Paper Numbers: SAE 800276, HS-029 194
  • Files: HSL, USDOT
  • Created Date: Jun 28 1984 12:00AM