By Paul Casciato

LONDON (Reuters) - Trampolinists whistle, tennis players grunt and Chinese women's superheavyweight weightlifting champion Zhou Lulu screams "Fung shong!"

Those are just a few of the noises athletes competing for medals at the London 2012 Olympics make in an effort to run, jump, lift, hit and shine at the top of the sporting world.

A packed crowd in London's ExCel arena roared as Zhou approached the platform to set a new world record on Sunday, screaming back at her as she shrieked in preparation.

Later, a demure and bespectacled Zhou smiled as she told reporters that far from a war cry, she was actually saying "Relax".

"So I can lift the weight, relaxing," she said.

At the trampoline, many of the athletes emit a short sharp whistle while sailing high in the air to execute the twists and somersaults which score them points with the judges.

Mental Performance Consultant Andy Barton told Reuters that some noises may be involuntary, but others such as the whistling may help athletes to stay in the performance zone, be part of a mental routine or are a trigger for movement.

"Noises are fantastic triggers," Barton said, adding that making noises may help some athletes remind their bodies of the next move to be executed.

"Some people are quite auditory and they feed off external sounds."

Barton said that athletes who have highly developed auditory senses can use external noise for their advantage.

"I was working with a showjumper the other day and she talks to herself, talking herself around the course."

He said Olympic silver medalist tennis player Maria Sharapova's grunting may be part of a routine, which may be why the Russian shot down questions about whether she might stop after complaints about her noises on the tennis circuit this year.

"Certainly not now as I have been doing it since I was four years old," Sharapova told reporters during Wimbledon in June. "It's definitely tough and impossible to do when you've played this sport for over 20 years."

Fencers shout and scream, stomp and argue, whipping off their masks to prance after a successful point, intensely aware that this is psychological warfare as much as it is physical.

It is common for both fencers to turn on the referee, shouting exuberantly in the hope of swaying a point their way even though there is now slow-motion replay to separate the great actors from the true winners.

In hockey, some of the Asian women's teams - China and South Korea - pretty much jabber throughout the whole game.

While most teams talk, shout and communicate with each other to direct players around the pitch, these sides literally just go on with no end, some have suggested to disrupt their opponents so they cannot hear each other's directions.

Barton said that there are bad external sounds which can put auditory athletes off their game, but one sound helping host nation Britain at the London Games has been the cheers of the home crowd, pointing to the deafening roar for six-time gold medal cycling champion Chris Hoy in his last race on Tuesday.

"That noise just drove him around that last bend."

(Additional reporting by William James, Kylie MacLellan, Annika Breidhardt, Tom Pilcher, Daniel Bases)