Cell phones get surround sound

British company adds the convincing illusion of three-dimensional sound for mobile-phone listeners.

Are those tinny ring tones making you jumpy? How about a new kind of phone that can make it sound like you're literally in the middle of a soothing forest stream?

A new line of multimedia phones has hit the streets in Japan over the past few weeks that incorporates three-dimensional sound technology from British start-up Sonaptic. As yet, the content for it is slim--a fishing game, a handful of sound and video clips--but the technology promises a substantial advance for mobile-phone audio.

The company's developers previously created the 3D audio technology for the Xbox, and they are now aiming to create a similarly compelling experience even with the constraints of a little mobile phone, they say.

"If you're going to hold a phone in your hand, the screen is going to be small, no matter what you do," said David Monteith, Sonaptic's managing director. "It's hard for it to have much impact, but you can make it much more immersive if you have better audio."

The company is aiming to capture a corner of a cell phone multimedia market that is expanding rapidly, particularly in Europe and Asia, where fast data networks are more advanced than in the United States. Companies are in the midst of launching video streaming and music download services, and have watched revenue from mobile games climb steadily for several years.

The Sonaptic technology is based on the science of "psychoacoustics," which essentially studies precisely how sound waves interact with the ear in order to create sound effects.

Traditional stereo is created by blending audio between two speakers, creating the illusion that a sound source is located between the speakers. Home theater systems with 5.1 or 7.1 sound perform similar tricks, mixing audio between each of the speakers to create surround sound.

The Sonaptic technique, as with other related technologies, is drawn from a study of exactly how the ear and brain perceive where a sound is coming from the shape and strengths of sound waves. The company's algorithms then subtly change sound waves so that they are interpreted by the brain as coming from different positions.

In practice, what this means is that a cell phone with two little speakers can create the illusion of sound around a listener. In a CNET News.com test of the new Japanese phones, the illusion was maintained fairly well, even when the phone was moved around

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