Abstract:

The Del Mar Fairgrounds, San Diego, hosted the IMSA Grand Prix for 6 years from 1987--1993. The project provides a unique long-term study of professional road racing noise in a unique setting, a narrow valley just east of the coastline and within an environmentally sensitive lagoon. Sponsors were required to perform community noise monitoring at selected locations in the adjacent hills and lagoon. Both human and bird responses were examined. The monitoring documented the hour by hour variations in the maximum and average noise levels at up to 12 separate locations. The results indicated the thresholds which would trigger community response, the sensitivity of the response to diurnal and short-term wind shift, the effect of the inversion layer, the effects on bird patterns, and the statistical distribution of vehicle noise levels for the IMSA class vehicle. Basic findings revealed community response was triggered when levels exceeded 70 dBA Lavg. Downwind levels tended to increase at 1 dBA/mph over 5 mph. When the track was within an inversion, levels increased 10 dBA. The mean vehicle level at 15 m was 105 dBA with a 4-dBA standard deviation.