1 point
*
“The SOFAR channel (short for sound fixing and ranging channel) … is a horizontal layer of water in the ocean at which depth the speed of sound is at its minimum” …
“The SOFAR channel acts as a waveguide for sound, and low frequency sound waves within the channel may travel thousands of miles before dissipating.” …
https://en.m.wikipedia.org/wiki/SOFAR_channel
2 points