Noise Levels of trucks, both interior and exterior, have been studied extensively in the last few years. However, most of these noise studies have been performed under carefully controlled conditions. This paper presents the results of two studies which were concerned with the noise level experienced by the truck driver during actual operation. The first study's purpose was to determine the noise level of actual operation while the second study compared actual operational noise to the noise level that was produced during three standard test methods. The three standard test methods were SAE Recommended Practice J336, high idle and constant 50 mph operation.