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Why can sonar noise travel hundreds of miles through seawater?

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Can bubble curtains protect harbor porpoises from noise pollution? — noise pollution Learn about the impact of underwater noise on marine animals, notably harbour porpoises.

Sonar noise can travel hundreds of miles through seawater primarily due to a phenomenon known as the SOFAR (sound fixing and ranging) channel.1

Located at depths of approximately 1,000 meters, this zone is characterized by a minimum sound speed resulting from the specific combination of pressure, temperature, and salinity at that depth. When a sound is generated by a point source within this channel, the sound waves become trapped by refraction. Instead of dispersing in three dimensions, the sound is channeled horizontally, which significantly reduces energy loss and allows the signal to propagate over vast distances.12

This efficient transmission of sound is a critical concern in noise pollution, as the long-range reach of naval sonar devices can interfere with the communication and echolocation abilities of marine animals, such as whales and dolphins, and has been associated with mass strandings.13