Bellow kitty: Merlin with his owner Tracy Westwood, who says she often has to turn up the TV

IT starts with a warble, a little like a creature calling out in the jungle.

Then it turns to a rumble, like a train approaching from afar, or the sound of someone revving a single-cylinder motorbike in the distance.

Is it a bird? Is it a plane? Er… no. It’s Merlin, the world’s loudest moggy.

With a growl that can drown out the noise of a dishwasher, he has just secured a Guinness World Record for the domestic cat with the highest decibel-rated purr.

It officially peaked at an impressive 67.8dB – about the same as the sound of a shower or two people holding a conversation. But no-one ever talked quite like this.

‘Sometimes on the telephone I do get people asking me what that noise is in the background,’ said Merlin’s owner Tracy Westwood. ‘I tell them it’s the cat – but I don’t know if they believe me.’

His formidable purr emerged soon after Mrs Westwood brought Merlin home from a rescue centre near her home in Torquay, Devon, 13 years ago. Even as a kitten, he could make more of a racket than a full-grown cat. The only living soul in the mother-of-two’s house that couldn’t hear Merlin was her oldest dog. (It was deaf).

Two years ago Mrs Westwood read about Smokey, a cat that held the loudest-purr record since 2011 with a 67.68dB rating. She instinctively knew Merlin could out-purr him.

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Mrs Westwood, pictured with her daughter Alice and Merlin, got the black and white cat from a rescue centre 13 years ago

‘Occasionally when he’s really loud I have to repeat myself,’ said Mrs Westwood. ‘When you’re watching films you have to turn the telly up or put him out of the room. I can hear him when I’m drying my hair.’

Recordings taken with a smartphone app clocked the black and white cat at peaks of between 98dB and 100dB, which, if accurate, would have ranked him alongside Maria Sharapova, one of tennis’s champion grunters; and only 10dB below the noise of a pneumatic drill.

So it was time to call in the experts. A sound engineer and an adjudicator from Guinness World Records duly arrived at the Channel 5 studio in which Merlin was making a bid for stardom as part of a TV show called Cats Make You Laugh Out Loud 2, being screened tonight (weds).

Using high-tech equipment, and holding a microphone 1m away and 1m above the ground, they registered Merlin’s purr at 67.8dB. The first two readings fell disappointingly below Smokey’s world record. But his title was snatched after Merlin was fortified with a bowl of tuna cat food. ‘It was amazing to see just how loud his purr was in person,’ a Guinness World Records spokesman said. ‘It was indeed a new record.’

Domestic cats normally purr at a comparatively puny 25dB. Pet behaviour expert Professor Peter Neville, who features in the show, said: ‘No-one is really sure why cats purr.’ He said they normally did so while relaxed and happy.

In which case Merlin must be one very contented cat. Yet although he is now the new purring champion, his voice is but a whisper in the animal kingdom. The inch-long pistol shrimp, which rapidly snaps its claw to stun prey with underwater sound waves, produces 218dB.

Merlin has secured a Guinness World Record for the domestic cat with the highest decibel rated purr. His growl peaked at 67.8db - the average cats is 25db