The startling discovery was presented on the BBC's nature series, Wonders of the Celtic Deep. Experts on the show tracked a pod of some 240 dolphins to learn more about the beautiful creatures in their natural habitat. It came as a surprise to them to find the bottlenose dolphins living in Cardigan Bay, on the west coast of Wales, "spoke" to each other at frequencies never before heard anywhere in the world.
In essence, the Welsh dolphins appear to have developed a localised dialect of sorts and their whistles are unusually fast.
Dame Sian Phillips, who narrates the series, said: "Bottlenose dolphins are highly sociable, the group are in constant communication.
"Each dolphin has its unique signature whistle and the Cardigan Bay dolphins may have their very own dialect.
"Their whistles are at a higher frequency than those recorded anywhere else in the world."
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Scientists had previously discovered the dolphins of Cardigan Bay are very unique, thanks to their voices.
In 2007, the creatures were studied by marine scientist Ronan Hickey of the University of Wales in Bangor, alongside experts from the Shannon Dolphin Foundation in Ireland.
The study recorded and analysed nearly 1,900 dolphin whistles in the Irish Sea to conclude the Welsh dolphins were truly unique.
Dolphins communicate by using a series of whistles and clicks, as well as barks and groans.
At the time of the research, Dr Simon Berrow of the Shannon Dolphin and Wildlife Foundation said: "Whistles are important to dolphin communities and individuals for recognition purposes.
"Calves are through to learn whistles of their mothers, and therefore that could mean whistles are evolving.
"We would like to do more research because this was a one-off analysis.
"But we've found there's a difference in their repertoire."
And dolphins are not the only animals to develop a regional twang in their vocalisations.
Scientists have previously found cow moos vary from region to region.
According to a 2006 study, researchers at the University of London examined cows in the West Country, after farmers claimed to have spotted a notable timbre in their voices.
One farmer in Glastonbury said at the time: "I spend a lot of time with my ones and they definitely moo with a Somerset drawl.
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"I've spoken to other farmers in the West Country group and they have noticed a similar development in their own herds.
"It works the same with dogs - the closer a farmer's bond is with his animals, the easier it is for them to pick up his accent."
This was then confirmed by Professor John Wells, according to whom the exact same phenomenon has been observed in birds - and not just parrots.
The expert explained: "You find distinct chirping accents in the same species around the country.
"In small populations such as herds, you would encounter identifiable dialectical variations which are most affected by the immediate peer group."
Scientists have also found sperm whales in the Caribbean have a distinct way of communicating when compared to other whales of the same species.
A team of international researchers studied the giant beasts and published their report in 2016.
They identified 21 unique codas - sequenced clicks - not seen in other parts of the Atlantic.
The researchers wrote: "Individual differences in vocalizations are ubiquitous among animals, but the degree of stereotypy we document in one socially learned coda type (1+1+3) among an entire population of sperm whales, and its stability across at least 30 years, is rare.
"This provides a remarkable example of cultural transmission maintaining high levels of conformity in behaviour across large numbers of individuals that are not continuously associated."