Quiet pavement is designed specifically to reduce highway noise. Many factors play a role in the generation of sound due to tire-pavement interaction. These include: 1) tire size, design, condition (new versus worn) and loading; 2) vehicle type, size, condition (new versus old) and speed; 3) traffic volumes; 4) pavement porosity; and 5) pavement surface texture. Assuming all other factors are constant, the traffic noise levels will vary with variation in pavement surface characteristics such as porosity or texture. Therefore, to minimize tire-pavement noise, the type of pavement surface and/or the associated texturization are of paramount importance. Tire-pavement noise has become an increasingly important consideration for highway agencies as the public consistently demands that highway traffic noise be mitigated. Although sound walls provide a means for addressing highway noise, improved pavement structures and surfaces may provide a competitive alternative for noise mitigation. While the approaches may differ slightly from agency to agency, the general practices observed include using both quieter pavements and noise barriers, as well as implementing policies that set noise level thresholds and seek noise reductions from both vehicles and tires. Overall, the European approach was found to be more comprehensive than U.S. practices, addressing nearly every aspect of noise reduction. As part of the effort in evaluating different methods for reducing noise level on freeways, MTO initiated a project by building five trial sections to examine the effect of various asphalt mixes in reducing the tire-pavement noise level. These include two types of open friction course, stone mastic asphalt, open graded rubberized asphalt concrete, and a control section. Immediately after construction, pavement noise measurements were performed using the ON-Board Sound Intensity (OBSI) method for measuring the noise level at the tire/pavement interface using a sound intensity probe. All five test sections were measured simultaneously, by driving the vehicle across the test area. Three different speeds, 60 km/h, 80 km/h, and 100 km/h were used. Multiple passes were undertaken to obtain at least 2 valid measurements per test section. This paper will present results of the investigation analyzing the effects of different mix types in reducing the noise level generated as a result of interaction between tire and pavement surface.
