As interest in surround sound for television and radio grows, research into new and different techniques to expand the audio picture continues apace, writes Kevin Hilton.
BBC Research and Development is looking into Ambisonics as a way of dealing with format compatibility, while King’s College London recently opened a new audio laboratory to concentrate on reproducing the experience of human hearing.
The BBC’s Ambisonics and Periphony project is based at R&D’s North Lab in New Broadcasting House in Manchester. Team member Anthony Churnside (pictured, left, with Richard Furse of Blue Ripple Sound positioning loudspeakers), winner of the RTS Young Technologist of the Year 2010 Award, has set up a listening room in an old radio studio to house an Ambisonic array.
This comprises 14 speakers, arranged as a cube – a square above and a square below – and six in a hexagon at listener head height. Two additional loudspeakers have been placed in the horizontal plane to allow comparisons between Ambisonics and mono, stereo and 5.1.
Recordings played back through this are made on Soundfield microphones. Among material that has been processed for Ambisonics are recordings of the 2009 Last Night of the Proms, and a radio production of The Wonderful Wizard of Oz. This was recorded in a radio drama studio, with the actors performing into a Soundfield mic. The final mix was a combination of B format ambience and mono effects.
Ambisonics has also been recorded in conjunction with the North Lab’s tests of a prototype surround video system. Churnside says that a “major potential advantage” of Ambisonics over discrete surround formats is its lack of dependency on speaker position.
The audio lab at King’s College London was formally inaugurated during August. It is based around a large isolation booth, claimed to be the second largest anechoic chamber in the UK.
The facility is headed by Dr Zoran Cvetkovic, who joined King’s College as a Reader in Signal Processing in 2004. He was previously at Harvard University and the Centre for Information Sciences Research of AT&T’s Shannon Laboratory.
Cvetkovic’s work is focused on recreating an accurate “auditory perspective”, which he says calls for a “humongous number of microphones” to reproduce the sensation of human hearing.
The King’s research is also attempting to create an enveloping experience. Cvetkovic says Ambisonics can offer this but the sweet spot is very narrow. “We want the sweet spot to be as big as possible,” he says.
Cvetkovic and his team is not considering surround for pictures at the moment but he says the proposed system could “definitely” be able used with moving images.