AKA: Echo test, Pulse test, hammer test, Pulse-Echo Method (PEM), Pile Integrity Test (PIT), Impulse Response, etc.

The Sonic Pile Testing is covered in ASTM Sonic standard D5882

In the Sonic test, the top of the pile is tapped with a lightweight plastic hammer and the reflected wave are recorded by a suitable computerized equipment. From the resulting signal, or reflectogram, one can determine both length and continuity of the pile.

In its most basic form, the sonic test measures the time between the hammer trigger, and the reflected wave, to indicate the pile's length. this is very similar to the famous Newton's cradle "executive toy".

An interactive simulation of the method is available here - (no setup required)

Although a powerful tool, the Sonic method also has limitations, such as:

A synthetic pile and the reflectogram