Pavement sound absorption measurements in the U.S.

In the U.S., the topic of pavement sound absorption in regard to tire-pavement noise has shown increased interest and research over the last several years. Four types of pavement sound absorption measurements with various applications are discussed: 1) In-situ measurement of effective flow resistivity (EFR), applying a modified version of ANSI S1.18-1999 - obtaining EFR values for pavements allows for direct input to the FHWA Traffic Noise Model to more precisely represent pavement sound absorption in the propagation algorithms. 2) Laboratory measurement of near-grazing incidence sound propagation properties over porous pavement, as compared to a perfectly reflecting surface - the results provide a descriptor of sound propagation at shallow angles of incidence, which cannot be predicted from absorption data alone. 3) Developing method to simulate the propagation of tire noise over pavement surfaces - the average sound intensity for a compact loudspeaker is measured along with resultant sound pressure levels at two distances, and the difference in levels is reported. 4) In-situ measurement of pavement sound absorption using an impedance tube mounted on pavement, part of ISO 13472-2 - method is used in the qualification of pass-by test tracks mandated by ISO 10844 and can be used in other applications where sound absorption is less than ∼15%.