Developing procedures for evaluating and reducing operator's noise levels is a common challenge for all machine manufacturers. Although individual approaches will vary with each individual, industry, or equipment type, the end result is a method to evaluate and develop the control of noise.One such approach used on large farm tractors with cabs is described in this paper. It describes the application of general sound control theory and some of the benefits obtained. Each modification made on the product has its own unique procedure for analysis. This paper does not assume these procedures will solve other noise problems, but they can be used as a guide.