Sony is packing its new Walkman digital music players with noise-cancelling and other audio-enhancing technology in its latest attempt to challenge the iPod.

"The strongest point is audio quality," said Hiroshi Yoshioka, corporate senior vice president of Sony and head of its Walkman division.

Front and centre of Sony's marketing will be built-in noise cancelling. The system is tuned to cancel out background noise in the 100Hz to 1kHz range like that often present on trains, aircraft or cars.

To do that, the system uses a microphone to detect the noise to be cancelled out. On the new Walkmans, that microphone is in the headphones, which means listeners must use the supplied headphones for the noise cancelling to work. In a demonstration on Thursday the headphones did a good job of cancelling out simulated train noise.

The noise cancelling is something that really has to be demonstrated to be understood, Sony said, so it is planning to offer such demonstrations in shops across Japan.

Two other features, both of which are headphone independent, include "clear stereo," a system that better separates the left and right channels and stops audio bleed between channels, and "clear base," which improves the bass response.

The players have a battery life of 50 hours, and can display album art on a small colour OLED (organic light-emitting diode) display panel. Listeners can search through their music by song name, album name or artist name.

The players are compatible with MP3, Windows Media, AAC, ATRAC, ATRAC Advanced Lossless and Linear PCM audio files. However, they won't play Windows Media or AAC tracks encoded with digital rights management: that limits downloads of DRM-protected tracks to stores using Sony's ATRAC system.

The new players, which will appear in Japan later this month and in other markets later this year, draw on Sony's history of audio engineering and Sony is aiming the devices at music fans. As part of this plan it will promote them through sponsorship of a series of events linked with Japanese cable TV music channels.

The S700-series, which come with noise cancelling and an FM radio, will come in versions with 4GB, 2GB or 1GB of storage. They will cost ¥29,000, ¥23,000 and ¥18,000 respectively.

In comparison the 4GB version of Apple Computer Inc's iPod Nano costs ¥23,800 in Japan and the 8GB version is ¥29,800.

Sony will also sell two models without noise cancelling or an FM tuner.

In related news, Sony Ericsson last night revealed it sold 19.8 million phones in its most recent quarter, including music-enabled mobiles.