Effect of sound source movement on radiated noise level

Abstract

Change in sound pressure level and A-weighted sound pressure level (Noise level) of radiated sound due to sound sources moving at the same constant velocity along a straight track is discussed in this paper. When sound sources move, frequency and amplitude modulation is observed in the radiated sound field. When the modulation is considered, calculated overall sound pressure level of the sources becomes larger than the calculated levels when it is not considered. The difference between maximum sound pressure level and the equivalent sound pressure level while the source is passing-by, with or without considering the modulation, increases monotonically with respect to source velocity. Source frequency characteristic depends on noise generation mechanism or structure of the sound source. Difference between calculated noise levels, with and without considering the modulation, increases as dominant source frequency decreases due to A-weighting below 1 kHz.