Noise exposure and convertible cars.

OBJECTIVE To investigate whether drivers of convertible cars are exposed to excessive noise levels. STUDY DESIGN Prospective. SETTING Data were collected along a main United Kingdom highway. SUBJECTS AND METHODS Seven cars were included within the study, encompassing a range in cost, power, and comfort. A calibrated, integrating noise meter was used to measure average noise levels (Leq dB) and peak levels (Lmax dB) encountered in the region of the driver's roadside ear with the convertible roof lowered. Readings were recorded at speeds of 50, 60, and 70 mph with the windows lowered and also at 70 mph with the windows raised. RESULTS Noise levels for all testing conditions had a range for Leq of 82 dB to 92 dB, whereas the maximum Lmax level noted for articulated lorries was 99 dB. CONCLUSION A minimal trend toward increasing noise levels with speed was noted for the speeds tested. A statistically significant difference in noise reduction was found by raising the car windows. Although average levels were noted to be above the 85 dB criterion level legislated by some organizations, the length and frequency of most car journeys with the convertible roof lowered is unlikely to significantly increase the noise exposure risk of most individuals. Future studies may be able to evaluate whether a temporary threshold shift phenomenon may occur.