Record labels are making music artificially louder so that your iPod can compete with traffic noise and background chatter. Purists such as Bob Dylan and The White Stripes are not happy. But do real people care, asks Brian Boyd

Why is music so LOUD these days?

It's nothing to do with your age. Music really has got louder over the past few years, and it's all because of how we now listen to people. Thanks to the MP3 revolution, much music is now listened to on the go, so it has to compete with the noise of traffic. Music also has to be louder to make an impact against rival competitions such as computer games.

WHAT?

It has been scientifically proven that music has gotten louder. Studio engineers are using digital technology to compress sound waves at the "mastering" stage of the record - the last part of the recording process. It's done at the behest of the label that owns the musical recording in question.

It's all very white coat stuff. But, essentially, sound compression works by reducing the peaks and troughs in music. There simply aren't many quiet passages in modern rock music. The dynamic range has been lost.

Remember those TV test tones they used to have and how annoying the sound was after a few minutes? That was because the tone had been super-compressed to eliminate any variation. Apply that thinking to modern music and you will understand the basics of how sound compression works.

When did music start getting loud?

There have been various studies in recent years in which audiologists have taken recently made albums and compared them with albums recorded before MP3s became common.

The studies all found that today's albums are compressed and are therefore not just louder but also suffer from what's known as "one-level distortion" - meaning whole layers of sound texture have been removed to ensure a uniformly loud sound.

Who started it?

Most people date sound compression from the 1999 release of the Red Hot Chili Peppers' Californication. This album was branded as "unlistenable" by recording studio experts on its release due to the extent of the sound compression on it. There is an online petition calling for Californication to be remastered so it can be "de-sound compressed". You'll find the petition at www.hydrogenaudio.org/forums/ lofiversion/index.php/t39305.html.

More recently, albums by Arctic Monkeys and Lily Allen have been sound compressed to sound louder. When asked to comment on why they were using sound compression, the Monkeys' label, Domino, said the sound compression was done to make the music more "impactful".

And what do the oldies think?

Bob Dylan told Rolling Stonemagazine last year: "You listen to these modern records, they're atrocious, they have sound all over them. There's no definition of nothing, no vocal, no nothing, just like - static."

And the knob-twiddlers?

Peter Mew, the senior mastering engineer at Abbey Road studios, has confirmed that labels are "competing in an arms race to make their album sound the 'loudest'. The quieter parts are becoming louder and the loudest parts are just becoming a buzz."

Mew, a leading anti-sound compression campaigner, also argues that sound-compressed music can induce fatigue in the listener simply because it's so relentless. On this point he is backed by the British Society of Audiology, which also found post-MP3 albums to be "more fatiguing".

Anyone else annoyed about it?

Angelo Montrone, a dissenting record company executive, has written an open letter to the industry detailing his concerns about sound compression.

"The mistaken belief that a super-loud record will sound better and magically turn a song into a hit has caused most major- label releases in the past few years to be an aural assault on the listener," he wrote. "This phenomenon is tantamount to a dessert chef deciding that since the frosting is the most exciting part, the cake should be all frosting.

"Prior to the mid-1990s, there was always some level of compression, done tastefully and left to the mastering engineer's discretion. This allowed some dynamic range. Things got loud, then soft again; the music could build, retreat and build bigger the next time."

But do the listeners really care?

So far the most vocal opponents of sound compression are professional studio recording technicians. Their ears are finely tuned and they know all about sound nuances and dynamics. Sound-compressed music makes them wince. There is a sort of analogy here with how cordon bleu chefs view the use of a microwave.

The average listener, though, simply doesn't have the auditory knowledge to distinguish sound-compressed music from non-compressed music. And because music is now increasingly listened to on MP3 players and has to compete with street noise, nobody seems to care much that it's louder.

Also, the younger generation coming up are experiencing sound-compressed music only. Give them an artfully arranged analogue (pre-digital) recording from the 1960s and they'll wonder why the music "disappears" every few moments. It hasn't disappeared at all - it's just a quiet bit.

The vinyl analysis

For the moment, sound compression seems to be an issue for purists and discerning listeners only, though newer bands such as The White Stripes go out of their way to record on analogue rather than digital. Analogue sound is much "warmer" than digital and it can't be compressed.

The larger problem concerns the general deterioration of music sound quality over the years. The transfer from vinyl to CD was the first big loss in sound quality (simply because of the shift from analogue to digital). There is arguably a bigger loss in quality when you transfer from CD to MP3, which is the auditory price you pay for being able to store hundreds of songs on a device the size of a matchbox.

So who will win?

There will be a reduction in sound compression only when consumers complain about sound quality. Of course, there will always be consumers who wouldn't countenance listening to music unless it's on thick vinyl and has been recorded and mixed on antique wood analogue devices (and preferably in candlelight, no doubt).

And then there are the rest of us, who have to listen to our latest downloads in rush-hour traffic. So just how far consumers are prepared to let sonic quality slide for reasons of convenience remains to be seen.