Investigations of Effects of Porous Pavement on Traffic Noise and Traffic Noise Prediction

The U.S. Department of Transportation's FHWA Traffic Noise Model (TNM) is currently missing the effect of sound-absorbing pavements on predicted noise levels, in regard to both a reduction in source level and a reduction of sound through propagation. In TNM, a single effective flow resistivity value representing acoustically hard ground is used in sound propagation and ground reflection algorithms. With acoustically hard ground, most of the sound from vehicles is reflected. For porous pavements (those with more than 15% interconnected air voids), sound incident on the pavement is partially absorbed and thus potentially reduces the noise level for receivers along the roadway relative to that for a non porous surface. Results of investigations indicate that the sound absorption produced by porous pavements will have an effect on both measured and predicted traffic noise levels. The work shows that more accurate TNM-predicted sound levels can be achieved by properly accounting for the sound absorption of pavement, the effect of sound-absorbing pavement is not insubstantial, and predictions can be made as to the effect of sound-absorbing pavement by using modeling or measurement techniques, or both.