Field evaluation of tire-road noise using a new close proximity method

A new close proximity (NCPX) method has been proposed and applied for the tire-road noise characterization of highway traffic. The implementation of NCPX is based on a set of surface microphones that is attached to a vehicle to directly measure the tire noise. To consider a combined effect of vehicle and road factors, a comprehensive field test has been performed with seven vehicle types at nine pavement sections of the test road. Testing parameters also include a vehicle speed ranging from 50 to 120 km/h, and two driving modes are applied at each speed: coasting and steady. It is found that asphalt pavements are quieter than all concrete pavements irrespective of testing conditions. Among concrete pavements, an 18-mm longitudinally-tined surface exhibits the quietest noise level, while a random transversely-tined surface is ineffective in minimizing the tire noise. Finally, the effect of a heavy axle load on the tire/noise generation is discussed.