During the development of a new type of road surface with very low tire/road noise emission, new vibro-acoustical characterization techniques for standstill conditions have been developed. First a method here called the COMPARATIVE RECIPROCITY has been used for determination of the road surface influence on sound absorption at leading and trailing contact edge (e.g. by abolishment of the horn effect and decreased radiation due to that). The reciprocal technique utilizes a miniature microphone only some millimeters from the leading or trailing contact edge. A loudspeaker positioned 2-3 meters from the contact is directed towards the contact patch. The difference between transfer functions for the standard dense reference surface and the highly compliant and sound absorbing poroelastic surface is determined. This will display a frequency dependent difference, which has been found to resemble the corresponding difference obtained by drive-by tests.
展开▼
