Acoustic Modality in Passive Detection Technology

Utilising the acoustic modality for passive detection and localisation of low-flying aircraft and gunshots is vital for border security and situational awareness. This paper presents a comprehensive experimental approach for detecting and estimating the direction of arrival of a single acoustic source using a single vector sensor and two different algorithms: acoustic intensity and velocity covariance. The study includes a thorough comparison of both algorithms for the direction of arrival estimation of a stationary continuous sound source, a hovering drone, and a propeller-driven two-seater manned aircraft flying at low altitudes in various environments. The research findings, which show that both algorithms provide similar estimates for the direction of arrival of the acoustic target in the frequency and time domains, provide a solid foundation for further exploration. Additionally, the results of an array of scalar sensors towards the direction of arrival estimation, using the cross-correlation method at the lab level, are also presented to complement the acoustic vector sensor. A system built around acoustic vectors and scalar sensors can serve as a passive surveillance and target detection system, providing a comprehensive solution for defence and acoustics.