Automotive Noise from a Motorway: Part II, Analysis

Modeling for automotive traffic radio noise is presented. A model is basic for single running vehicles with ignition-system radio emissions on a roadway. An equivalent source for the impulsive noise, continuously distributed over the distance traversed by a vehicle, with the same source density, is assumed to be acting only for the differential time length which is required for a vehicle to run through the differential distance. Based upon this model, the impulse amplitude distributions at the input to a narrowband receiver are derived mathematically, when a vehicle runs through a definite distance at a constant speed. Applications of the derived formula for the distribution are discussed in detail for the cases: 1) when the traversed distance varies, 2) when the emitting characteristic of impulses of the ignition system varies, and 3) when many vehicles with various emitting characteristics of impulses run on the roadway for a time long enough to provide statistically stationary data for automotive traffic radio noise.