This buzzing, chirping sound is the pulsing chatter of the tiny transparent Danionella cerebrum as heard by the human ear. Researchers in Germany were intrigued by the noise coming from the fish tanks in their lab and decided to investigate the source. Using underwater microphones, they quickly deduced that this species was no small fry when it came to communication.
This is the slowed down sound booming out like a heartbeat. The fish uses its muscles to strike its own swim bladder to produce a short loud sonic pulse. In the waters close to the fish, it taps out 140 decibels, which is as loud as a gunshot.
Researchers believe this quirky communication behaviour evolved in the murky streams in Myanmar, where the fish lives. Other fish, including the Plainfin Midshipman, and the Black Drum are louder, but also much bigger creatures.