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Phoning home quietly could net sound engineers £50,000

July 03, 2001

Telling the whole carriage which train you're on could be a thing of the past thanks to new 3D audio technology targeted for incorporation into the next generation of mobile phones. The engineers who may have saved travellers from each other's small talk are now in line for Britain's biggest engineering prize, the Royal Academy of Engineering MacRobert Award, for their audible innovation.

A team of engineers at Sensaura Ltd originally developed their 3D Positional Audio system to enhance classical music recordings. They realised that computers were a much bigger market and developed it as software that now runs on over 50 million PCs worldwide. It provides truly immersive "surround" sound for game-players and MP3 music listeners through conventional stereo speakers.

But the team soon realised that their virtual sound reproduction could also revolutionise mobile phone conversations. Sensaura technology can enable callers taking conference calls to "hear" different callers speaking from different positions around them - all via the same handset. The caller's voice can be made to sound as though it is coming from a metre or so in front of the listener, instead of the current, unnatural "in-the-ear" voice. The technology is also being developed to provide an improved form of digital noise-cancellation, creating a "bubble" of silence at the listener's ear into which their caller's voice can be virtualised, and consequently they will be less likely to shout when replying.

These advances are possible thanks to the Sensaura team's deep understanding of the way we hear sounds and how we determine which direction they come from. We can hear in three dimensions, although we only have two ears. "The secret lies in the way our head and ears are built," says Sensaura's Principal Scientist Dr Alastair Sibbald. "They act like a complex, directionally-dependent acoustic antenna." Incoming sound waves are diffracted around the head before they reach the eardrum so the brain receives a slightly different signal from each ear. There is also a time delay between the signals reaching each ear - our brains combine all this information to tell us where to look for the sound.

"Artificial heads" - with microphones for ears - are established as a way to model human hearing. Sound recordings made using these produce a 3D effect that includes the natural audio cues. "We have developed ways to synthesise these acoustic effects," says Dr Sibbald, "but the commercially available artificial heads were not precise enough, so we created our own pair of perfectly matched 'digital ears' to get the data we needed. It enables listeners to programme the sound output to their own head shape to get bespoke surround sound."

Sensaura™ 3D Positional Audio has already become a standard for PCs and is particularly in demand for games, where it provides a completely immersive audio world. Gamers can distinguish sounds from above and below as well as behind them. The system is now being applied to consoles themselves as well as PCs, with Sensaura technology to be used on the eagerly anticipated Microsoft Xbox™ video game system.

Dr Sibbald and his colleagues David Monteith (Managing Director of Sensaura), Richard Clemow, Peter Clare and Adam Philp will receive their MacRobert Award finalist certificate from HRH the Duke of Edinburgh on Monday 9 July at the Academy's AGM in London.
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Royal Academy of Engineering