The mechanical impedance is a measure of the ability of a structure to resist motion when subjected to a given force. It has been considered related with tyre-road noise level of road surface. However, this parameter is seldom used to characterize mixtures in asphalt mixture design. In this study, the relationship between the mechanical impedance and the pavement stiffness is investigated based on laboratory and in-situ measurements. Mechanical impedance is tested by an impedance hammer device, while the stiffness is measured by the indirect tension test (ITT) method. Different types of road surfaces are taken into account, including thin layer noise reducing surfacing, dense surface and poro-elastic road surface. The influences of mixture compositions on mechanical impedance and stiffness are discussed. Statistical relationship between the stiffness and the mechanical impedance is developed based on the measurement results. Advices for noise reducing road surface design by considering mechanical impedance are given according to the research findings.@en

Noise produced from the tyre-road surface interface is one of the most important contributions to the overall traffic noise and there is an increasing requirement for predicting the tyre-road noise levels prior to road construction in the Netherlands. In practice, a model with a simple structure as well as a high accuracy is applicable in road engineering. Also, material properties are preferred to be used as input variables of the prediction model, which will facilitate the pavement design. Based on these considerations, models are developed for evaluating the tyre-road noise from the asphalt mixture compositions and road surface characteristics. They are statistical models developed from the measurements on thin layer surfacings in the Netherlands. Different regression methods, model types and input variable combinations are taken into account. The selection of the model is due to the fitness of the prediction and validation by using measurement data from in service road sections. Two models, which evaluate the tyre-road noise level from the surface characteristics and from material properties, respectively, are finally selected. By using these models, only a small number of input variables are required and reliable predictions can be provided. The models achieved in this study can be used for predicting the tyre-road noise generation in road engineering and investigating the influence of surface characteristics and material properties on tyre- road noise levels.@en