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Alternately, some MP3 players support so-called lossless compression formats, alternatives to MP3 files that use more disc space, but do not discard any of the original audio data. Apple has its own lossless format, which listeners can create by ripping their CDs using its iTunes software, and which can then played on the iPod. Windows Media offers a lossless format but it’s not widely supported in devices. An alternative open source Windows format called FLAC, in which some artists including Metallica and Gillian Welch have begun distributing music, is supported by some iRiver and Cowon MP3 players.

Many device makers are also studying ways to manipulate the audio signal itself, in order to mimic the sounds of larger stereos, surround-sound speakers, or even live performances.

A number of companies, including iRiver, Samsung, and SanDisk, use technology from SRS Labs, which draws on psychoacoustic principles–essentially the physics of the way the ear collects sound waves, and the brain perceives them–to modify the audio.

In some cases, these features add the perception of deeper bass than small headphones can actually produce, by introducing subtle mid-range harmonics that might be produced by those lower bass tones. An analogous signal-processing trick is used to create the perception of speakers set farther apart than ordinary earphones.

In its latest generations of players, Samsung has added its own proprietary version of this signal-processing technology, called the Digital Natural Sound Engine Portable, which simulates surround sound through stereo headphones. For its part, Apple has eschewed this type of tool in its iPods, sticking with more traditional graphic equalizer settings and a “Sound Check” feature that equalizes the playback volume of songs recorded at different levels.

However, even these minimal signal-tweaking tools remain controversial for some audiophiles, who are often suspicious of any tampering with the original recording.

“I leave that stuff off,” Blackwood said. “I’m still a bit of a purist when it comes to playback, only wanting to tweak the audio to compensate for my surroundings.”

All of these subtleties ultimately depend on the quality of the speakers producing the sound, however. Most of the earbuds distributed with MP3 players are passable at best, with little ability to replicate deep bass tones, and only average clarity in accurately reproducing subtle sounds such as cymbal brushes or acoustic instruments.

Sony’s introduction of noise-canceling technology into the device itself, with a microphone in the MP3 player that senses and counteracts ambient noise, raises the stakes considerably. Rival executives say they’re watching to see how consumers react to this development, but no one has yet promised to follow suit.

“It’s a way in which device vendors can differentiate themselves, and we expect to see similar strategies, if not identical ones, over time,” said IDC analyst Susan Kevorkian. “But frankly, an important issue to consider is consumers’ perception of good enough. For many, even if music sounds sub-par … the perception is that it just isn’t that bad.”

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