Main Project Report : Noise and Texture on PCC Pavements (2000)

This report represents the second phase of a project sponsored by the Wisconsin DOT and the FHWA researching the texture and noise characteristics of Portland cement concrete (PCC) pavements. The team of Marquette University and the HNTB Corporation measured noise, texture and friction of 57 test sites in Colorado, Iowa, Michigan, Minnesota, North Dakota and Wisconsin. During 1997, new test sections were constructed in Wisconsin, including random transverse, skewed and longitudinally tined PCC pavements. Interior and exterior noise was measured on all 57 sites using the Fast Fourier Transform method with a Larson-Davis two channel real time acoustical analyzer. Subjective testing of interior noise was measured on 21 selected sections with 24 subjects with good hearing in a closed acoustical environment. Texture on all test sites was measured with the Road Surface Analyzer (ROSAN). Sand patch tests, a measure of surface texture, were also performed on most of the 22 test sections in Wisconsin. Highway noise cannot be characterized by one single type of noise measurement. For this reason, conclusions were drawn using the data acquired from all of the different measurements. These include: exterior, interior, subjective, and prominent frequency noise analysis as well as texture characteristics. Some pavement textures exhibit a definite distinctive noise that is often described as “a whine”, and is exhibited as a prominent tone or discrete frequency also described as a “spike”. Generally, the longitudinal tined PCC and the Asphaltic concrete (AC) pavements exhibited the lowest exterior noise levels. The AC pavements and the longitudinally tined and random skewed PCC pavements and the European texture exhibit the lowest interior noise levels. ROSAN texture measurements were relied upon and proved invaluable in analyzing the reason why different textures exhibited different noise characteristics. The ROSAN mean profile depth (MPD) and estimated texture depth (ETD) correlated very closely with sand patch. There was good correlation between tining depth and width, using the ROSAN data, and some of the loudest transverse tined pavements had both greater depth and widths, but it could not be determined which was responsible for the greater noise. Spectral analysis of the ROSAN outputs was utilized to recommend the proper random pattern for transverse tining. The patterns were tested in 1999 and both subjective and objective analyses confirmed the lack of discrete frequencies. Conclusions include that tining depths vary tremendously among the pavements constructed, even within a single test section, uniform tined pavements exhibit a discrete frequency or whine and should be avoided, transverse tined pavements with the deepest and widest textures were often the noisiest, longitudinal and random skewed tining (1:6 skew) can be easily built, eliminate discrete frequencies while substantially reducing noise levels, and random transverse tining must be carefully designed to eliminate discrete frequencies, but may not substantially reduce overall noise levels. When comparing different pavement textures with the same mean texture depth (approximately 0.7 mm) to that of uniform 25 mm, transverse tined PCC pavements, a well randomized transverse will result in a 1 to 3 dBA exterior noise reduction, a random skew 4 dBA, a longitudinal tined 4 to 7 dBA and an opened textured AC pavement 5 dBA, based on this study. Interior noise reduction were approximately half of the exterior reductions. Recommendations include improving the quality control over tine spacing depth and width, future research on wet pavement accidents and longitudinal tining and the relative affects of tining depth and width on tire pavement noise, and specific recommendation on when to use longitudinal, random skewed and random transverse tining. Long term monitoring of noise differences of these 57 test sections is recommended in order to determine if surface texture differences can be reflected in FHWA noise models.