The quarter-inch long water boatman can reach volumes of almost 100 decibels – as loud as a crack of thunder – by rubbing its penis on its stomach.
The process, called stridulation, is done to attract a mate.
Researchers in Glasow used specialist underwater microphones to record the insect and found that the average water boatman reached 78.9 decibels - about the sound of a passing train.
Engineering expert Dr James Windmill from the University of Strathclyde, who led the study, said: “We were very surprised. When we identified without any doubt the sound source, we spent a lot of time making absolutely sure that our recordings of the sounds were calibrated correctly.”
Luckily for anyone living near a river most of the sound is made underwater and 99 per cent of the volume is lost.
The song of a blue whale can hit 188 dB but once size is factored in the tiny waterboatman is Mother Nature's biggest noise.
Dr Windmill said: "If you scale the sound level they produce against their body size, Micronecta scholtzi are the loudest animals on Earth."
He also confirmed that scientists were baffled at how the insect is able to produce such an din with a penis only 50 micrometres across - about the width of a human hair.