In-situ measurements of traffic noise on several roads in Algeria

This study presents an experimental methodology to investigate the correlation between tire rolling noise and pavement surface characteristics, specifically roughness and texture. Measurements were conducted using the two primary methods employed to assess the influence of road surfaces on traffic noise: the Pass-By Method and a Close Proximity-like (CPX-like) method. The latter utilizes a tire different from the ISO reference tire and a microphone placed in a potentially semi-reverberant cavity. Initially, noise level predictions from the Federal Highway and RLS 90 models were compared with Pass-By Method measurements near urban areas, rather than with L_A,eq values, as is commonly done. The validation process demonstrated that the Federal Highway model provides more accurate results in this environment. Subsequently, extensive traffic flow measurements were carried out on a broad road network in Algeria, supplying input data for the prediction model and enabling noise level forecasting. Findings indicate that, during both day and night periods, noise levels frequently exceed the thresholds set by national regulations, particularly on rough pavements. The CPX-like method, implemented with non-standard equipment, was then employed to measure tire-road noise during vehicle rolling, following system calibration using a Brüel & Kjær (BK) 2270 sound level meter as a reference. The experimental procedure assessed noise signals generated by tires across various road sections, examining both smooth and rough pavement surfaces. The adherence and Longitudinal Friction Coefficient (LFC) varied across sections due to differing traffic loads, including light and heavy vehicles. Additionally, a test section paved with semi-granular bituminous concrete (SGBC 0/14) was analyzed, revealing that the particle size distribution of aggregates plays a role in noise reduction. Experimental results suggest that further adjustments to this formulation could lower instantaneous tire-road noise levels. Comprehensive roughness, texture, and friction measurements across multiple road sections confirmed that the CPX-like method’s sound level readings correlate with surface roughness, particularly the Mean Profile Diameter (MPD) and LFC. A decrease in MPD was associated with a 2 dB reduction in noise level, while an LFC of 0.25 led to an increase of 2.5 dB.