Linden Lab plans next week to launch limited beta tests of voice chat in its Second Life virtual world.

The voice chat will be designed to simulate real-life speaking, with voices getting fainter as the speakers' avatars get more distant. Residents will be able to perceive the direction that voices are coming from.

"You'll be able to walk into a group of people and, if all those people are in conversation, you'll hear voices emanating from their locations relative to you," said Joe Miller, VP of platform and technology development for Linden Lab.

The technical implementation of that is complex, he said. It's not like ordinary streaming audio -- which is already available in Second Life -- where every listener hears the exact same audio. With the new voice feature, "every avatar receives a custom audio stream relative to their position relative to the speakers," Miller said.

Avatars will get more animated as the speakers' voices get louder. The avatars' nametags, which normally float above the avatars' heads, will change to reflect who's speaking. As with just about everything in Second Life, the animations and nametag-changes will be fully customizable -- residents will be able to write scripts to change their own avatars' behavior, and get scripts from others.

Linden Lab expects voice to be particularly useful for academic institutions holding lectures in Second Life, corporations using it for training, and friends just chatting with each other, Linden Lab said.

The limited beta program will be used on a test grid for 1,000 users. Formal launch will be around May, when voice will be enabled throughout Second Life. Users will need to have a headset connected to their PC, and will be able to speak to each other on voice-enabled areas of Second Life as soon as they log in, without having to modify the client software.

Linden Lab will allow voice to be switched off on privately owned areas of Second Life, and residents will be able to opt out of voice, continuing to use text chat and instant messaging.

The voice capabilities will be integrated into in-world instant messaging -- so residents can communicate with each other even if their avatars are in distant regions of the world -- and in group instant-messaging.

Linden Lab is providing the voice capabilities in partnership with Vivox. The technology uses a codec called Siren14, which provides high degrees of compression without lost quality. The codec accurately reproduces sounds in the 5 MHz to 14 MHz range, much broader than most codecs, which will make it ideal for reproducing music, Miller said. Listening to live music is a popular activity in Second Life.

Until now, Second Life residents looking to add voice to their experience have had to rely on third-party applications, such as Skype. Or they picked up the regular phone and called.