A novel approach to localization of environmental noise sources: Sub-windowing for time domain beamforming

Abstract

This article brings a breakthrough in understanding the computation of direction of arrival (DOA) of sound waves and represents an important step in the further introduction of spatial domain into environmental noise and acoustics measurements in general. Instead of improving the accuracy of beamforming, it makes more sense to increase the number of DOA calculations in the time domain and to use the statistical properties of environmental noise to localise the noise sources. We know from experience that two noise sources never have the same frequency characteristics, operating times, and spatial locations. This is the foundation on which the presented research stands and is validated with experiments. The high frequency sampling of 192 kHz allows a subwindow approach to time domain beamforming and the subdivision of microphone signals into time intervals of less than one millisecond. This allows statistical analysis of the immission directivity during the typically used time constant of 125 ms. The calculation of DOA in the subwindows shortens the time needed to evaluate the contribution of each noise source to the total sound pressure level. This leads to more data points (immission vectors) and lower statistical error in environmental noise measurements. In this paper, we propose associating the temporal dominant direction with the temporal sound pressure level within the subwindow and integrating the results to determine the immission directivity. Numerical simulations, experiments and practical application of the sub-windowing differential beamforming algorithm (SubW-DBA) method provided promising results.