Which term is used to describe the long-range propagation of sound in the ocean due to refraction in the SOFAR channel?

• A. Sofar Layer
• B. Surface Zone
• C. Sofar
• D. Shadow Zone

Answer: (C)

The long-range propagation of sound in the ocean via refraction in the near-minimum speed layer is described by the term Sofar. In the ocean, sound speed decreases with depth to a low point and then increases again with depth due to pressure. This creates a natural waveguide: sound rays bend toward the slower-speed region and become trapped around that depth, allowing acoustic energy to travel great distances with little attenuation. That trapping effect is what people refer to when they say Sofar propagation. The Sofar layer is the actual depth band where the speed minimum lies, not the propagation mode itself, while surface-zone and shadow-zone terms describe different features of sound in the ocean.