ASSESSING OUTDOOR SOUND ATTENUATION WITH SWEEPS IN A TIME-VARYING ATMOSPHERE

Abstract

Measuring outdoor sound attenuation is essential for various purposes, including studying outdoor sound propagation, evaluating noise prediction schemes, estimating attenuation when the simulation is not an option, or assessing the in-situ performance of noise abatement measures. A very successful technique that has superseded maximum length sequences (MLS) in room and building acoustics, sine sweeps have also been used outdoors. However, the outdoor environment is notoriously timevarying. There are claims that sine sweeps are less vulnerable to time variance, but no evidence for this. The purpose of this paper is to test these claims. The effect of time variance was investigated numerically in the theoretical case of a homogeneous flat ground and a time-varying non-homogeneous atmosphere. The impact of time variance on excess attenuation spectra is discussed in the corresponding time-invariant scenario. The results also indicate that sine sweeps perform better than MLS in the context of time variance.