Development of a portable system for acoustical reconstruction of tunnel and cave geometries.

Abstract

Noninvasive remote determination of the geometry of caves, tunnels, and piping complexes has value for both military and commercial activities. Troops that must enter caves, tunnels, or urban storm sewer piping systems, for example, would be greatly aided by first knowing the distance to the next turn, opening, branch, or closure. A system employing a sound source and a pair of acoustic sensors was developed to do this, based on the medical techniques of acoustic laryngometry and rhinometry, and has been demonstrated both in laboratory and in full‐scale field situations. Acoustical reflectometry techniques are first used to compute an area versus distance profile of the passageway under interrogation. Other procedures are then used to classify and characterize the various types of “junctions” that could give rise to the observed changes in area (branching versus a simple area expansion, etc.). Results obtained using a prototype field system in full‐scale tests indicate that small arms fire can be used in ...