Sound travels much faster in water than in air, but the distance it covers is significantly influenced by ocean temperature and pressure. These factors create a unique phenomenon that allows sound to propagate over vast distances.
Imagine a whale communicating with its pod deep in the ocean. The sound waves it produces spread outwards, but their journey isn’t straightforward. As sound waves travel deeper, decreasing temperature causes them to slow down and refract, or bend, downwards. This bending continues until the waves reach the thermocline, a layer characterized by rapid changes in temperature and pressure. The thermocline’s depth varies geographically.
Below the thermocline, the temperature stabilizes, but pressure continues to increase with depth. This increased pressure causes the speed of sound to increase, resulting in the sound waves refracting upwards.
This interplay between temperature and pressure creates what’s known as the “sound channel,” or SOFAR (Sound Fixing and Ranging) channel. The sound channel acts as a waveguide, trapping sound waves and allowing them to travel thousands of miles with minimal energy loss. The channeling effect is so pronounced that hydrophones, specialized underwater microphones, strategically placed within the sound channel can detect whale songs and even man-made noises from kilometers away. This makes the ocean a surprisingly noisy environment, and understanding how sound travels is crucial for studying marine life and monitoring ocean conditions.
