Occupational noise exposure of operators of heavy trucks.

Over 400 measurements were taken across Canada to assess the noise exposure of truck operators. The exposure of the driver was evaluated using both 3-dB (Leq) and 5-dB (L5dB) exchange rates. Driving with windows closed and radio not operating resulted in the lowest exposure. The drivers' Leq ranged from 78 to 89 dBA, with a mean of 82.7 dBA; operating the radio increased the mean by 2.8 dB; driving with the driver's side window open increased the mean exposure by 1.3 dB; and driving with the window open and operating the radio resulted in an increase of 3.9 dB. Trucks with cabs mounted over the engine appear to be quieter than standard trucks by about 2.6 dB. Operations on four-lane highways are 1.6 dB noisier than on two-lane highways, most likely as a result of higher speeds on the former. Long haul (city-to-city) operations on hilly terrain appear to be quieter than on flat terrain by about 2.2 dB, again probably indicating the strong effect of speed. Regression analysis was used to obtain relationships between a number of variables such as Leq and L5dB, etc. These measurements indicate that the exposure of a driver is almost certain to exceed the current threshold limit value for noise (85 dBA for 8 hours with a 3-dB exchange rate) when driving with the radio on and the driver's side window open. Comparable numbers in terms of L5dB are also reported.