Ultrasound testing (UT) is based on the property of ultrasound waves to propagate in homogeneous materials and be reflected by any discontinuities which may be encountered - materials of various acoustic properties (resistance), or non-homogeneity (defect) in the material.
The ultrasound waves propagate from the source of ultrasound through the material being tested.
If there is a defect in the material, behind it, depending on the defect, the waves will weaken or will not appear (reflected by defect).
