Measuring the transmission velocity of sonic pulses through a given material is commonly referred to as a sonic test.

In these tests, a wave is induced by the impact of an instrumented hammer, and its reception is recorded through an accelerometer (speeds or accelerations may also be recorded).

Knowing the distance travelled by the wave (measured on site) and the travel time of the wave (by the difference between the moment of impact and the moment of reception), we can determine the propagation speed of the sonic wave.

This speed is related to the greater or lesser compactness of the material traversed by the wave, and in particular its stiffness. 

These tests allow us to, for example, estimate the greater or lesser compactness of a material – to detect defects or cavities in elements and evaluate their uniformity – in a non-destructive way.