Lab

Noise-cancelling headphones

Air conditioning, traffic and plane engines are just some of today's insidious sources of audio interruption. You can crank up the volume on your MP3 player, but it'll never drown out the decibels of modern life - and it could do permanent damage to your ears. Noise-cancelling headphones offer a more sensible and scientific solution.

Over the next few pages, we look at six of the best anti-noise units, at prices ranging from a relaxing £22 up to an ear-popping £225 for the most luxurious way of simulating silence.

The science bit

Rather than blocking out background noise physically, noise-cancelling units use the physical properties of sound waves to actively reduce the impact of the sound around you. In basic terms, microphones on the exterior are used to create an inverted waveform of the ambient noise - an 'anti-sound' wave which creates disruptive distortion to significantly reduce those troublesome frequencies.

It's not a simple process, which explains the relatively high prices of the products on test. Getting it right means processing the sound with no effective delay and at a high enough quality to make the two waves match accurately - something that simply wouldn't have been possible a few years ago. It's an imperfect science, and none of these units will give you the impression of walking into a totally silent room. But the best come close.

There's more to consider here: not only how the noise cancelling technology affects what you're listening to, but also how good the 'phones are to start with, working passively, and whether this is an option when you don't need to cut out noise or you've run out of battery. Then there are the ergonomics: the weight, the quality of the lead and how easily it tangles, not to mention how the units look when strapped to your head.

Comfort is important if you're going to be wearing your headphones for long periods, or perhaps even sleeping in them on a plane, so we've rated that highly. They also need to be durable and convenient to pack.

Price and priorities

While sheer quality is naturally rewarded in our scoring, all of these headphones are more than good enough for everyday use, and it would be a waste to throw good money after low-quality MP3 files. Top-end headphones will accentuate any flaws in the original audio or the compression applied to the music file. You only need to consider the best sets if you're in the habit of filling your MP3 player with huge top-quality audio files.