Assessment of Acoustical Measurement Methods and Standards on Rubber Asphalt Roads

Abstract

This paper focuses on the availability of reliable and widely recognized standards for measuring the tyre/pavement noise by determining the existence for a common or certified standard for measuring the asphalt rubber road noise and the possibilities of establishing a common standard or making enhancement to the current standard for accurately measuring the noise. A noise measurement study is conducted using one of many methodologies recognized internationally on both conventional and asphalt rubber road. The noise measurement study is based on the Statistical Pass-by method which is described in detail in the International Standards Organization ISO 11819-1. Certain modifications have been made in order to suit the local environmental condition during the measurement. The most significant modification from the ISO 11819-1 is the distance of the microphone location that is used in the noise measurement from the center of the test road. The ISO 11819-1 stated the microphone position as 7.5m distance from the test road. However, in North America, 15m distance is commonly used. The proportions between noise source dimensions and microphone distance are affected in such a way as to reduce the potential difference between LAmax (maximum sound pressure level) and LAE (Single-event sound exposure level) [2]. Simulations can be done to find out the influence of the microphone distance to the accuracy and reliability of the test measurement readouts besides the advantages and the disadvantages on using both microphone distances from the test road. To further prove the reliability of the study, the results are then analyzed and compared to the predicted noise level using the Traffic Noise Model (TNM) developed by the Federal Highway Administration (FHWA). The FHWA's TNM that computes highway traffic noise is constructed based on the large amount of vehicle noise-emissions database and has been made comparisons to at least five other different model results or real noise measurement study to verify the accuracy of the model.