It was a bizarre phenomenon that troubled researchers for decades – a mysterious under sea ‘quacking’ heard every winter and spring in the depths of the Southern Ocean.

But now experts believe they have finally established the origin of the noise. They say that the distinctive duck-like sound is produced by the undersea chatter of Antarctic minke whales.

According to Biology Letters, researchers attached microphones to two of the marine mammals and heard them making the strange sound.

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It was first detected by submarines in the 1960s and since then, the repetitive, low-frequency noise has been recorded many times in deep, uncharted waters around the Antarctic and western Australia.

At first, scientists believed the noise could have come from another submarine. Others posed theories involving ships and fish, but none have provided conclusive evidence until now.

Denise Risch, lead researcher for the US National Oceanic and Atmospheric Administration (Noaa), said: “Over the years there have been several suggestions... but no-one was able to really show this species was producing the sound until now.

“It was either the animal carrying the tag or a close-by animal of the same species producing the sound”.

Scientists don’t know why the minke whales produce the sound, but it is believed to be a form of communication between the mammals.

The team hope that the discovery of the sound’s origin will allow them to learn more about the whales, which have rarely been studied.

“Identifying their sounds will allow us to use passive acoustic monitoring to study this species,” Dr Risch said.

“That can give us the timing of their migration - the exact timing of when the animals appear in Antarctic waters and when they leave again - so we can learn about migratory patterns”.

Scientists have recently solved another acoustic mystery in the depths of the South ocean. A low frequency noise called ‘the bloop’ was found to have been caused by the sound of ice cracking.