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Immersive audio for Planet B

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Caleb Knightley | 10:31 UK time, Thursday, 29 October 2009

Planet B is a science fiction series on BBC 7, the second series starts on the 29th November. You can read more about series two of Planet B on the Radio 4 blog.

Before you read on, you should put your headphones on and listen to this...

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With any luck you should have just had an interesting if not mildly disturbing sonic experience. And - by the way we don't really have your brain on a database; it was all just a sonic illusion..... As with all great Sci Fi special FX techniques it was done using a technique that was created a very long time ago and then re hashed in the 70s. The technique is called Binaural and has more or less been around since the dawn of broadcasting, when the French used it to broadcast operas though the telephone network to paying customers. It was originally patented in 1931 by Alan Blumlein as part of his pioneering research into Stereo for EMI.

Now if your not really interested in recording techniques you can stop reading now, as the rest of this blog will be as painful as sitting next to the really boring guy at a dinner party who talks about how the ABS in your car works...for hours. For those of you who are interested, you can read this and laugh at me, saying 'no, no, no - you so called BBC so called expert, you clearly have done it all wrong!'

Anyway, Binaural is a stereo recording and playback technique that tries to recreate sound in a three dimensional way. Surround sound for headphones. For true modern binaural recordings a 'dummy head' should be used with microphones placed inside replica ears, but there are a few variations on that theme. The basic idea is that two omni-directional microphones are placed a heads-width apart and are separated by a head-like object. So when listened to on headphones the sound appears as it would if you where really there. The drawback is that it only works on headphones and is in no way compatible with summed mono, i.e. the single speaker DAB radio in your kitchen. Also, as it is still just an illusion that tricks your brain, people can experience dummy head binaural in different ways. A common complaint being that all the sound seems to be coming from behind the listener.

A clever person has already written this wikipedia page on Binaural if you are interested in finding out more. And there's more on Dummy Head recording here. And a clear demonstration by a very nice chap on YouTube here. And there are other binaural shorts on You Tube including a virtual haircut which is fun;

BBC Radio Drama did an excellent play using binaural called The Revenge in the 70s with no dialogue. It's totally gripping and well worth a listen if you can find it. There are also many music recordings using binaural including some tracks on Pearl Jam's 'Binaural' album.

For the Planet B Immersive trail you just heard we actually used three different types of stereo. Those being 2 track Mono, L and R stereo and Quasi Binaural stereo.

The Quasi Binaural elements were captured in a few different ways. For the opening scene the voice of planet B says 'Thank you for choosing to upload your brain' while the probe moves around your head - we used two different techniques. For the vocal element I recorded the actress in a standard voiceover way with a Mono cardioid large diaphragm condenser mic; in this case a Neumann U87. This was then played back through speakers in the studio's live area positioned at opposite poles around a Jecklin Disk microphone array. (The disk was chosen over the dummy head for its better compatibility with data compression techniques).

The probe effect in the first scene was achieved by playing back the probe sound FX through a Fostex self powered speaker which was moved around the mic array manually. In the end it took three very quiet people to move the speaker, and my Phillips Shaver for extra intensity.

For the three scenes Spy world, Jurassic Adventure and Operation Extreme Glory, all the vocal elements were recorded using the Jecklin Disk, including the background voices in Spy World and the screaming soldiers in Extreme Glory.

The final binaural elements are the brain removal sequence. We again used the three person Fostex speaker dance for the sawing of the skull. The disk was then replaced by a melon and a coconut. These were operated upon with various implements and much fun was had by those of us listening on headphones to the squishing and scraping.

The rest of the sound design was done in L and R Stereo, and panned Mono using some spatial plugin's. It was all recorded, designed and mixed within the excellent Pro Tools HD. The in-studio SFX playback was done using Spot On play out software. We monitored using Sennheiser HD25-1s and Beyerdynamic DT250s. The recording console was a Studer Vista 6.

For me it was an interesting experiment in sound, combining different stereo techniques to create a unique listening experience. But really it was all down to the BBC Radio Drama Development team in coming up with such an excellent idea, and a brilliantly imaginative script!

Caleb Knightley is a Senior Studio Manager and Sound Designer for BBC Radio Drama.



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