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kind of acoustic attenuation speed is very small, for example, components made
by fine texture steel and other small components made by various materials.
However, if ultrasonic waves propagate long distance in material, highly
accumulated acoustic attenuation may be produced (even if material acoustic
attenuation is very small). This may lead to danger of underestimating natural flaw
size, so estimate the influence of attenuation in evaluation and take it under
consideration when necessary. If surface of tested objects is rough, a part of
incident sound energy will be lost due to beam scattering on object surface, this
affects detection. When scattering gets stronger, reflection echo gets lower,
leading to bigger errors in evaluation results. So it is very important for the echo
amplitude that the surface condition of the tested objects.