Abstract
The spherical acoustic radiation model had been employed for a prediction of sound propagation from open ends of exhaust pipes based on a presumption that sound pressure expands in a spherical form. But it was revealed by sound intensity measurements that sound pressure did not necessarily propagate spherically depending on engine operating and silencing conditions. Therefore, a new sound propagation model utilizing a finite difference method was developed. By using this calculation method, (1) a prediction of sound propagation was able to calculate even in a case that a spherical acoustic radiation was not formed and (2) an envelope form of the sound pressure waveform dependent on time can be predicted with satisfactory precision.