What term describes the weakening of sound as it propagates through a medium?

• A. Attenuation
• B. Amplitude
• C. Area
• D. Bandwidth

Answer: (A)

Attenuation is the loss of sound intensity as it travels through a medium. As the ultrasound beam moves, energy is absorbed by the tissue (often turning into heat), scattered out of the beam, and reflected at interfaces, all of which reduce the forward-propagating energy and cause the signal to weaken with depth. This weakening is quantified as attenuation (often in dB/cm/MHz) and tends to increase with frequency, which is why higher-frequency ultrasound has better resolution but less penetration. Amplitude refers to the instantaneous peak displacement of the wave and does not capture the cumulative distance-related loss, while area and bandwidth describe other properties not directly about propagation loss.