Acoustic system for Low Flying Aircraft detection

Low Flying Aircraft (LFA) have been used in illicit activities across borders as they are difficult to detect by radars. Stevens Institute of Technology has developed and built an Acoustic Air Detection (AAD) system that can detect, track and classify small aircrafts, helicopters and ultralights. The AAD consists of several nodes, where each node has five microphone clusters. Initial signal processing is conducted at each node, where the cross-correlation of signals between various microphone pairs is used for finding the acoustic signal direction of arrival. Limited acoustic signature and bearing information from each node is sent via a microwave link to a central processing station, where triangulation of the directions of arrival from two or more nodes allows for target localization. Special developed software separates acoustic signals of various Targets of Opportunity (TOO) from other manmade and natural sounds. A network of four AAD nodes was operated in a mountainous area for more than 10 months and during this time (which included changing seasons with high winds, rain and snow), the AAD system performed without interruption.