Ambient infrasound noise in urban environments

Abstract

Associated with the emerging use of infrasound at tactical ranges (less than 50 km in complicated terrain), there is an increased need to deploy infrasound arrays in urban environments near sources of interest in order to record small signals. Initial urban deployment research demonstrated successful monitoring of a single source within 1 km utilizing rooftop infrasound arrays. In order to understand the applicability of this technique for a broader range of sources, the impact of the urban array design on noise reduction and detection of signals of interest must be assessed. These source signals, recorded within an urban scenario, are embedded in a complicated ambient noise environment with multiple coherent clutter sources and an overall decrease in the signal-to-noise ratio. Understanding these ambient acoustic field characteristics requires deconvolving observed coherent signals from time-varying atmospheric effects for different levels of urbanization. This paper presents an initial approach to instrumenting the urban environment with consideration of wind filter effects and data analysis to estimate total ambient acoustic field for a subset of urban zones. This work then provides a definition of urbanization that can be related to the infrasound wavefield. Permission to publish was granted by the Director, Geotechnical and Structures Laboratory.