The Deep Ocean Noises We Still Can't Identify

The SOFAR (Sound Fixing And Ranging) Channel, also called the Deep Sound Channel, exists at 200-1000 meters depth where sound travels minimal speeds but maximum distances. Scientists discovered this during 1960s experiments when Australian explosives were heard in Bermuda 20,000 km away.

NOAA scientists discovered Upsweep in 1991 when monitoring Pacific Ocean hydrophone arrays previously used for Soviet submarine detection. The sound remains unidentified after 30+ years of continuous recording.

The US Navy deployed SOSUS (Sound Surveillance System), a classified network of passive sonar devices throughout Atlantic and Pacific Oceans during the Cold War to detect Soviet submarines.

The ocean contains 26 marine mammal species, approximately 35,000 fish species, and nearly 250,000 marine invertebrates. Many are soniferous (sound-producing), creating a complex acoustic environment scientists are still cataloging.

Nicknamed “52,” this whale has vocalized at 52 Hertz since 1989, far higher than typical blue or fin whale frequencies (15-25 Hertz). Scientists dubbed it “the loneliest whale” believing its unusual pitch prevents species interaction.