Which term denotes the layer within the ocean where the sound channel exists and enables long-range propagation?

Which term denotes the layer within the ocean where the sound channel exists and enables long-range propagation?

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

Answer: (A)

The main idea is that the ocean’s sound speed changes with depth in a way that creates a natural acoustic duct. As depth increases, temperature and thus sound speed drop in the upper layers, but at greater depths the increasing pressure raises sound speed again. This creates a layer where the speed of sound is at a minimum, forming a guided path for sound waves—the SOFAR layer. Because sound travels slower at that depth, rays tend to bend toward this layer and stay trapped within it, allowing energy to travel long distances with relatively little loss. The term for this layer is the SOFAR layer (Sound Fixing And Ranging channel). The other options don’t describe this waveguide: the shadow zone is the regions outside the duct where sound energy is sparse, the surface zone is the warm upper layer with higher sound speed, and surface tension is unrelated to sound propagation in seawater.

The main idea is that the ocean’s sound speed changes with depth in a way that creates a natural acoustic duct. As depth increases, temperature and thus sound speed drop in the upper layers, but at greater depths the increasing pressure raises sound speed again. This creates a layer where the speed of sound is at a minimum, forming a guided path for sound waves—the SOFAR layer. Because sound travels slower at that depth, rays tend to bend toward this layer and stay trapped within it, allowing energy to travel long distances with relatively little loss. The term for this layer is the SOFAR layer (Sound Fixing And Ranging channel). The other options don’t describe this waveguide: the shadow zone is the regions outside the duct where sound energy is sparse, the surface zone is the warm upper layer with higher sound speed, and surface tension is unrelated to sound propagation in seawater.