Impact-acoustic testing is a method of free vibrations, based on excitation of freely attenuated elastic vibrations in a test object or part of it and an analysis of these vibrations parameters.
The advantages of impact method over other low-frequency methods are the ability to test products made of materials with small Young's modules and high damping coefficients of elastic vibrations (rubber, foam, etc.) and detection of flaws at a greater depth (up to 30 mm in plastics).