US Patent 7281878 Road surface sound reduction system

A method for reducing tire to road noise generated by vehicles on a road surface comprises generating a pseudorandom unique line pattern, providing said pattern as transverse grooves disposed in the road surface, said grooves being randomized according said line pattern as to one or more of position, frequency, and depth so as to spread the noise spectrum thereby reducing the amplitude or volume of noise generated at any single frequency and are capable of dramatic reductions in noise generated by high speed traffic on roadways. It can be implemented by conventional construction practice at little or no additional cost and eliminates the need for costly structures such as noise barrier fencing in residential areas.