Synthetic Aperture Acoustic Imaging for Roadside Detection of Solid Objects

A synthetic aperture acoustic system was developed to detect roadside threats including IEDs and landmines. The technique uses audio-band sound broadcast from a compact trailer-mounted system to image the roadside perpendicular to the travel path. The area adjacent to the travel path is insonified and the microphone records the reflected acoustic signal. The travel of the transceiver creates a synthetic aperture that allows imaging of the scene. During the earlier phase of the project, a compact system was deployed, and experiments with pulse diversification was undertaken as well as a study of the effects of travel speed and path errors. Data was collected at Fort AP Hill, and at the Night Vision Laboratory. The processed data were and further analyzed for characteristics and features amenable for discrimination. Additional design specification for a vehicle based SAA system was developed in conjunction Night Vision staff. Work related to measuring acoustic properties of both natural and anthropogenic materials relevant to outdoor imaging was executed. This work required the development of hardware such as vertical impedance tubes for both low 200-2000Hz and mid frequency 500-8000Hz ranges. The report presents and discusses results for several case studies of SAA imaging and acoustic material property characterization.