Acoustic Leak Detection

Pinpointing a leak on a pressurised line by listening to the sound it makes escaping. Ground microphones, listening sticks, and correlators are used to narrow the loss to a point on the surface so the repair excavation can be sized to the break.

A pressurised leak radiates sound into the pipe wall and into the surrounding soil. On metallic pipe that sound carries a long way, which is what makes correlation between two contact points practical. Plastic pipe absorbs the higher frequencies that carry the signal, so acoustic range drops sharply and hydrophones that couple directly into the water column at hydrants and valves are used instead. Where the pipe damps sound too heavily, tracer gas is the usual fallback because it does not depend on pipe material at all.