Maximum Fast time-weighted levels - When can a transient be seen as a Dirac impulse?

Abstract

It is common practice to use maximum FAST time-weighted sound pressure levels to assess transient impact noise, as these levels correlate well with human perception of impact noise. Maximum FAST time-weighted levels are known to be dependent on the reverberation time of the receiving room. In previous studies, an analytical correction term was developed using a Dirac impulse. The correction term is used to calculate the maximum FAST time-weighted levels from peak sound pressure levels. Peak levels are independent of the reverberation time of the room. Applying the correction term makes it possible to compare measurement results from different rooms. The correction term has been validated in several studies for the standard rubber impact ball. In this paper, the influence of the source signal (Dirac impulse) on the correction term is studied. Analytical and numerical models are employed to investigate the consequences of stretching the impulse in time and of changing its shape. The results are compared with empirical solutions developed in other studies.