Prediction of Pavement Materials' Impedance Using Ultrasonic Pulse Velocity

ABSTRACT There are many factors that influence tire/pavement noise such as road friction and acoustic absorption as well as pavement texture. Highway noise is addressed through several models such as Traffic Noise Model (TNM) developed by the Federal Highway Administration (FHWA) of the United States. The TNM computer program is capable of predicting highway noise, but currently does not take into account the pavement type, or specifically allow the input of pavement material properties. The objective of this study was to develop a mathematical model to calculate the acoustic absorption (impedance) of pavement materials. The model developed was based on mix volumetrics for the specific pavement type. Knowing the volume of each component in the pavement mixture, dampening properties such as the Ultrasonic Pulse Time (UPT) for acoustic wave transmission and the Effective Flow Resistivity (EFR) through the material can be obtained. The scope of work included the evaluation of the dampening properties of different pavement materials obtained through laboratory testing; and validating the results using a predictive model. The Ultrasonic Pulse Velocity (UPV) testing method was adopted to assess the dampening properties of pavement materials. The experimental program included the evaluation of 31 laboratory pavement specimens and 49 field cores obtained from national and international pavement sections. A total of twenty three different pavement types were evaluated. Correlations between predicted and laboratory measured UPT was excellent. The UPT results were used to calculate the EFR, which is the direct main input into the TNM. Correlations between tire/pavement noise levels and laboratory calculated EFR for each of the field mixtures were excellent and rational in that lower the EFR, lower was the tire/pavement noise level for a pavement material. Since the EFR is used as a main input into the FHWA Traffic Noise Model (FHWA TNM), the model and test data collected in this research will prove to be a potential enhancement to a wider use of different pavement types into the Ground Zones module of the TNM.