Attenuation in ultrasonic testing arises primarily from which combination?

• A. Reflection and refraction
• B. Absorption and scattering
• C. Diffraction and reflection
• D. Dispersion and reflection

Answer: (C)

Attenuation in ultrasonic testing is the decrease in signal strength as the wave travels through a material. This happens because energy is removed from the forward beam through two main interactions: diffraction and reflection. Diffraction causes the wave to spread and bend around obstacles, redistributing energy away from the straight path, while reflection at boundaries, flaws, and interfaces redirects energy back toward the transducer or into other directions. This combination reduces the amount of energy continuing along the original path, which is what the received signal reflects. Absorption and scattering also contribute, especially at higher frequencies, but the described pair explains how energy leaves the forward beam through geometric spreading and boundary interactions.