Acoustic and seismic signals of heavy military vehicles for co-operative verification

To analyze the potential of ground sensors for co-operative verification, the Bochum Verification Project has measured sound and soil vibration produced by military vehicles. Both signals contain contributions from the engine which usually dominate in the acoustic channel. With tracked vehicles, the track produces additional components which dominate the seismic signal at close to medium range and render it more than ten-fold stronger than that of wheeled vehicles. The acoustic amplitude decreases roughly with the inverse distance, while keeping the signal shape. The seismic amplitude decreases faster, but shows local variations; the seismic signal shape varies strongly with position. Acoustic and seismic spectra consist mostly of harmonic line series, caused by the engine and, if present, the track. Acoustic and seismic sensors can detect heavy vehicles passively, independent of weather and daylight, at more than 100 m range. More complex tasks, such as vehicle-type recognition or trajectory determination, require further research.