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June 2014 l 29


broadcastnews In parallel with this,


researchers have also been using Ambisonics for 3D sound. Ambisonics was devised during the early 1970s by recording engineer and mathematician Michael Gerzon, with recordings made through a specially designed SoundField microphone to produce an accurate audio picture comprising absolute sound pressure level and the three pressure gradients: left/right, front/back and up/down. But BBC R&D decided that binaural was more effective for the height element in 3D sound, and produced a number of test recordings, including a radio drama production of The Wizard of Oz (which gave the sensation of objects being thrown about by the tornado that takes Dorothy to the fantasy land) and a recording of Elbow in concert.


During a demonstration of this work in 2011 a BBC R&D spokesman said much of the


work had focused on “how to personalise characteristics [for] accurate localisation” of the sound to suit each individual listener. To make this possible, a head-tracking device is now part of the process, and special apps that can be attached to devices such as Bluetooth receivers – so the wearer is able to receive all the spatial audio information, even if they are moving about while wearing the headphones – are under development. To make this work, the dummy head has been replaced by software to process six-channel surround-sound recordings, preserving head- related transfer functions (HRTFs) – the variations in sound frequency caused by the ear, head and shoulders. Recent BBC productions made using 3D sound include the Nine Lessons and Carols concert and radio drama Private Peaceful, although these were based on standard surround signals converted into binaural.


MediaCityUK in Salford Quays, Manchester, UK – home of the BBC’s R&D department


The reappearance of this old technology has not been well received in some sections of the technical press. As well as observing that the “sexing up” of binaural as 3D sound would not make up for existing “imperfections” in the format, one commentator pointed out that sounds could be potentially disconcerting and


even dangerous for someone listening while out walking or riding a bicycle.


Despite such negative reactions, the BBC is confident 3D sound/binaural will have a new lease of life. “There are lots of potential applications for binaural sound and when done really well it’s very convincing,” comments Chris Pike, senior


scientist with BBC R&D. To appeal to a younger audience, and playing on recent trends, engineers have been working to integrate sound recorded on smartphones and tablets into broadcasts of concerts and other live events.  www.ambisonic.net www.bbc.co.uk/rd www.binaural.com





Photo: University of Salford Press Office


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