Absorption, reflection and scattering of the incident sound beam equal which phenomenon?

• A. Attenuation
• B. Refraction
• C. Diffraction
• D. Doppler

Answer: (A)

Attenuation is the loss of the ultrasound beam’s energy as it travels through tissue. Absorption converts some of that energy into heat, reducing the beam’s amplitude. Scattering and reflection divert energy away from the forward direction—scattering sends it in many directions, and reflection sends it back toward the transducer or into other tissues. When these energy losses accumulate along the path, the transmitted signal diminishes, which is exactly what attenuation describes.

Refraction is the bending of the beam at interfaces due to a change in sound speed, not a net loss of energy. Diffraction is the bending of waves around obstacles or through openings. Doppler involves a frequency shift caused by motion, not attenuation.