| Over 50 percent of the United States population is exposed to traffic noise at a disturbance level of 70 decibel, while 15 percent are subjected to noise levels even higher and are considered an actual nuisance. Porous portland cement concrete pavements reduce noise at the source and have been very successful in Europe. A method was developed to predict the aggregate and concrete porosity and that was verified by image analysis. A laboratory manufactured impedance tube was developed to test the acoustical performance of the samples. Relationships were determined between the porosity, sample depth, aggregate type and acoustical performance. Detailed instructions were provided for a transportation agency to repeat the procedures described. |
