Aspects of rumble strip noise at distant ranges

One aspect of rumble strips that limits the use of these devices is noise intrusion for residents nearby the roadway. To investigate this issue as part of the NCHRP quieter rumble strip project, pass-by noise measurements on the rumble strips were made beyond the standard evaluation distance of 25 feet (7.5m). Distances varied from 48 feet (14.6m) to 381 feet (116m) more typical of distances for residences near the roadway. For this assessment, pass-by noise measurements and recordings on the rumble strips were made at distances using one test vehicle from the primary research. The measurements were for sinusoidal rumble strips with wavelengths of 13, 15, 16, and 17 inches (33.0, 38.1, 40.6, and 43.2cm). For comparison, measurements were also made for more standard, discrete grind rumble strips. For all strips, the frequency of the repetition rate was apparent as the vehicle approached the microphone location and to a lesser amount after the vehicle passed the microphone. It was also demonstrated that the overall A-weighted level fell-off at a higher rate than the level at the repetition rate. The 80 Hz tone from the sinusoidal strips was observed to be barely audible, unlike the 100 Hz tone for the conventional strips.