Doctor Who Knock Knock binaural sound 3D Peter Capaldi
BBC has released an enhanced version of the Doctor Who episode “Knock Knock” with binaural sound that simulates 5.1 surround sound via stereo headphones. It puts the audience in the middle of the action as the Doctor (Peter Capaldi) and Bill (Pearl Mackie) explore a seemingly haunted house. Not to worry, those creaking floorboards and walls are just filled with man-eating wood lice controlled by the Landlord (David Suchet). The eerie atmosphere was perfect fit for the sound effect says Doctor Who producer Nikki Wilson.

“The reason why this episode lent itself so brilliantly to the binaural mix is because of it being a kind of horror, playing with the horror genre and the trope of that,” Wilson explained on BBC’s Click. “And a lot of what makes things scary, I think, is what you don’t see. And building up the atmosphere to that moment of scare is really what the audience are looking for.”

Binaural sound was first used by the Théâtrophone to bring opera to the masses via stereophonic telephone lines in 1881. The century old technology is finally catching on says BBC Audio Supervisor Catherine Robinson.

“The reason why binaural is really taking off now is because we’re in the age of the smartphone and the tablet and people are consuming their media with headphones,” Robinson said.

Doctor Who Knock Knock binaural sound - Doctor (Peter Capaldi), Felicity (Alice Hewkin), Harry (Colin Ryan)

Sound idea

Binaural sound uses stereo headphones but it doesn’t simply shift back and forth explains the BBC Research & Development team.

“If you have a certain sound somewhere in the room, then obviously it’s picked up by two ears, but it’s slightly different when it comes to these two ears,” Lead Technologist Frank Melchior told Radio Times. “The sound maybe arrives earlier in one ear than it does in the other ear. And this difference is between the two signals.”

The audio tracks are recorded in monaural, or mono, then a binaural algorithm is added in post production. The end result is a combination of three different processes.

“One element is you have a certain difference in timing, so a delay,” Melchior summarized. “Then you have a certain difference in level, so gain, essentially. And then you have a very complex equaliser on top of this, which models the outer ear and all the things that happen to the ear canal and so on.”

The binaural version is only available through the BBC iPlayer. If you are outside the UK, the easiest method is to add the Chrome extension Beebs – Access BBC iPlayer. Be sure to delete any BBC cookies then wait 5 minutes before visiting the BBC website. Of course, you should only use this method if you are a UK citizen, who is currently out of country.

Doctor Who “Knock Knock” enhanced version: