It has been noted that there are consistent differences between sideline sound levels measured on the two track types used for standardized motor vehicle passby testing, i.e. ISO and SAE surfaces. When the two-microphone transfer function method was first used in conjunction with a two-parameter ground model to characterize the acoustical properties of these asphalt surfaces it was found that there were significant acoustical differences between the ISO and SAE surfaces. However, it was also noted that environmental conditions, e.g. wind and temperature gradients, affected the estimates of surface properties obtained by using that method. In the present work, a ray tracing algorithm has been used to model the effects of environmental refraction on short range propagation over asphalt, and a physically-based single parameter ground model has been used to characterize the asphalt surfaces. It has been found that when the ray tracing procedure is used in conjunction with the two-microphone method, surface acoustical properties can be estimated under a wide variety of environmental conditions. The ray tracing and ground impedance models introduced here can also be used to predict the effects of varying surface properties and environmental conditions on passby measurements.


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    Title :

    Two-microphone measurements of the acoustical properties of SAE and ISO passby surfaces in the presence of wind and temperature gradients


    Additional title:

    Messung der akustischen Eigenschaften von vorüberfahrenden Fahrzeugen nach SAE und ISO bei Wind- und Temperaturgradienten, mit Hilfe von zwei Mikrophonen


    Contributors:


    Publication date :

    1997


    Size :

    15 Seiten, 23 Bilder, 3 Tabellen, 18 Quellen




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




    Two-Microphone Measurements of the Acoustical Properties of SAE and ISO Passby Surfaces in the Presence of Wind and Temperature Gradients

    Hartwig, T. J. / Bolton, J. S. / Society of Automotive Engineers | British Library Conference Proceedings | 1997




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