Abstract
Thin layer wearing course is commonly used as a noise-reducing pavement in some European countries. The noise-reducing performance is realized because of small surface texture and higher sound absorption properties. In this paper, the investigation focuses on the sound absorption properties of this type of road surface. Laboratory measurements were carried out to observe the sound absorption curves of the thin layer surfacing course. Both slab specimens produced in the lab and cores drilled from practical road sections were involved in the tests. It was found that surfaces with an air voids content less than 12 % show a smaller sound absorption coefficient, whereas surfaces with air voids content higher than 17 % have promising sound absorption properties. Acoustical models were also developed to describe the sound absorption of the thin layer wearing course. The modeling curves fit the test results better when connected air voids were taken into account. The models are considered applicable for examining the sound absorption coefficient with given mixture compositions, and they can also be used for evaluating the tire-road noise for a thin layer wearing course.
