Tire noise from open grid bridge decks

Having identified that the contribution to the overall noise from the grid vibrations is insignificant, the attention is focused on the noise radiated from the vibrations of the tire. Field measurements of tire vibrations are rather difficult, therefore laboratory measurements and analytic modeling were used to understand the contribution from the tire vibrations. The laboratory measurements of both vibration and radiated noise compare well with the estimates from the analytic modeling. Using an estimate of the interaction force between the tire and the grid, from the field vibration data, it is shown that the estimated radiated noise level is comparable to the field measured noise level at the curb. This leads to the conclusion that the noise from the tire vibrations is the dominant source, and mitigation procedures must consider ways of reducing the excitation of the tire. This conclusion is verified by sound level measurements performed with the contribution from the grid vibrations removed. [Work sponsored by FDOT.]