Transmission of Noise Into Passenger Compartments

The paper examines the mathematical hypothesis which forms the basis of calculation of noise-levels in passenger compartments. Without such means of theoretical evaluation, determination of noise-levels can only be accomplished by measurements of actual model prototypes.

The equation on which this calculation of noise-levels is based was formulated from measurements of passenger compartment noise and related variables. The quantities which define the noise-level include the noise-emitting surfaces, the emission factor, the transmission function which describes the coupling connection between noise source and the body, the noise-damping characteristic of the wall separating the engine and passenger compartments, and the absorption capacity of the passenger compartment. Further investigations are required for improved methods of determining some of these variables.

The equation is shown to be essentially correct for calculation of total noise levels. Certain implications of the equation are reviewed.