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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.

Pomona International Raceway, Pomona, California is the premier venue for drag racing sanctioned by the National Hot Rod Association. Community noise was studied for 9 years from 1984–1993. The project provided a unique long-term study of professional drag racing noise at 14 locations in a built-up community adjacent to the starting line. The object was to establish a basis for documenting the effects of noise mitigation’s planned for a renovated facility. The study revealed startling diurnal variations in noise, year to year variations, and the wide variety of emission characteristics of racing types. The simultaneous community and trackside locations permitted accurate correlation of events and established the basis for predictive models. The large data base permitted creation of a benchmark location by which the construction mitigation measures could be verified in a statistically valid manner. The study also revealed that the data spread is so wide that only multiple event sampling will provide an accurate picture of the community noise levels.