On the addition of two incoherent unsteady noise records of different statistical structures

The present study is a follow-up of two previous studies of the second author in an attempt to understand the importance of the statistical structures of noise records in affecting that of the resultant noise records formed from their addition. The present results show that the difference in the shapes of the cumulative distributions of the combining noise records plays a dominant role in the process. It is also found that the commonly adopted logarithmic addition tends more to underestimate the L10 instead of overestimating it as in the two previous studies regardless of the statistical structures of the noise records. The distributions of maximum over-estimation of the noise climate, the L10 and the L90 appear to be independent of the statistical structures and show insignificant diurnal variations.