Berlin - Many a person has looked in vain for the noise disturbing them while working or gaming at a PC - could it be a lawnmower or an airplane? -only to discover that the noise is actually from the computer.

There's no doubt that the loud rattling of a ventilation fan can annoy. But it should only take a little work to silence an older one. And, as for newer ones, most are made to work silently, say experts.

One problem is that it's hard to tell when shopping whether a computer will be quiet or not.

Kirstin Wethekam, who heads the multimedia group at Stiftung Warentest, a German consumer products tester, says high performance computers for gamers are among the noisiest.

That's because these machines don't just have fans for the processor and the power pack, but also for the graphics card.

“Otherwise, the high frequency graphic chips on these cards would get boiling hot,” says Christian Herzog, a manager at Bitkom, a German technology industry association.

Nonetheless, the industry has taken steps to quiet the machines down in recent years. Herzog also notes that devices purchased online can usually be returned if there are complaints.

“That's why a lot of manufacturers make sure their fan is not an infernal noise device.”

Wethekam agrees that manufacturers have woken up to the problem. A recent test of notebooks and ultrabooks showed all devices scoring between good and satisfactory when it came to operating noise.

Many ultrabooks, which come with energy-saving processors, high-end housing and a graphic chip directly on the processor, are often somewhat quieter than standard notebooks, but also more expensive.

There are also some certificates that grade devices on noise emitted, though they are not used universally.

Herzog says a PC advertised as running quietly should emit no more than 45 decibels when idle.

If the goal is to quiet an existing machine, there are multiple options.

One easy approach is to install a new fan with larger blades, which pull the same amount of air into the computer, but with fewer rotations.

Herzog notes that an older trick, a device that would control the rotations, no longer makes sense, since most fans' speeds are regulated by the temperature of the processor or graphics chip, and not set for a certain number of spins per minute.

A computer can also be quieted by deactivating unnecessary components.

Windows' energy management function includes settings that stop the hard drive spinning for certain periods. Separate graphics cards are also usually easy to turn off with a simple switch.

Herzog also notes that some desktops include processors with passive cooling.

“It's a big metal block with vents. When combined with a good blast of air, the computer is as quiet as a tablet.”

Casemodders - people who like to personalize their computer's housings -get even more creative.

The trend is mostly about appearances, but many of their modifications can also make the computer quieter, explains Alexander Gliserin, who has judged casemodding contests.

Some enthusiasts have stolen the idea of water cooling from the car industry. But that's usually only necessary for “high-end computers, in the super performance category,” says Gliserin. - Sapa-dpa