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The rise in smartphone usage and the increased availability of mobile data connections brought about a rise in the number of people listening to audio through their headphones over the past few years.
Most of the sound we listen to is in a stereophonic format and has been balanced for loud speakers, artificially split in to two identical channels. When listening to this centralised stereo sound through headphones, we are given the impression that the audio is coming from inside our head.
In contrast, binaural sound technology aims to create a richer listening experience. By manipulating audio recordings in post production, the smallest of sounds in each ear can be altered, creating an immersive experience for the listener where they can hear sounds in all directions around them, as if they were present at the time of recording.
"When you've heard binaural sound which has been balanced for use on headphones to avoid that effect of everything being right in the middle of the head, you realise how much better it is," said audio innovator Rupert Brun.You can pinpoint exactly which direction the sound is coming from in all three dimensionsRupert Brun, audio innovator
"If it has been done really well, you can pinpoint exactly which direction the sound is coming from in all three dimensions. For example, if you are listening to audio that has been recorded in the middle of a wood on a windy day, the sound of the wind blowing through the trees will be all around you."
Binaural sound is not a new concept. In fact, in 1881, those that lived in Paris with two telephone lines could listen to the opera binaurally by holding one receiver against each ear, each one replicating what an audience member would have heard out of their left and right ears at the event.
Traditionally, binaural sound is recorded by physically placing a microphone in each ear of a person or model. As long as the listener has the same head density and head shape as the person who recorded the audio, as the head and ear structure affect the way sound waves are picked up by the microphones, the sound would make for a truly immersive experience.
Difficulties arose over the years when producers came to edit the material, so the adoption of this technique was held back.
"When content is recorded in a binaural fashion, it is hard to edit and manipulate in post production," Brun said.
"You see, if you play binaural sound on stereo speakers it won't work particularly well."
Now, with advanced editing suites, producers are able to render traditional surround sound into binaural sound, which is enabling them to simply adapt the audio recorded on a single microphone in to a binaural immersive experience for headphone users, an approach known as 'headphone surround sound'.
"If you are used to producing stereo sound, you'll need to get a sound card that has more outputs on it and some surround sound speakers at your editing work station.
"Produce the content as surround sound in a conventional way, and then at the end when you have finished it, you've got your surround sound version that you can fold down to make a stereo if you want normal stereo distribution, or you can use a plug-in to create a binaural version," said Brun.
Brun is yet to find a free binaural plug-in that is any good, although he recommends noisemakers, which costs €80. "You can make your programme just as you normally would and then do the binaural editing at the end, providing you have some sort of surround sound element in the content," he said.There is still a lot to be explored within virtual reality, and sound is going to be playing a huge role within thatHenrik Oppermann, Visualise
He also explained that browsers are becoming so powerful that they can render surround sound to binaural for us automatically, such as when the BBC broadcast its drama Under Milk Wood. He said this advance in technology to create binaural sound was "quite stunning".
Head tracking
Binaural audio is still within its infancy, and the concept still has some challenges to overcome, most notably 'head tracking'. This concept relates to the movement of our head in relation to the sound we are hearing.
For example, Brun notes that if a headphone user is listening to a binaural recording with an orchestra in front of them, for example, for a truly immersive experience the listener should be able to hear the music louder in their left ear when looking to the right and vice versa.
"It is possible to measure the movements of your head and change the rendering so that the band stay in the same place – when you do that you get an absolutely, totally convincing realistic representation of being at the concert," said Brun.
"Your mobile phone has enough processing power to render surround sound as binaural audio if you've got a decent phone and it has got motion sensors."
But, as Brun notes, unless you are going to walk around with your phone attached to your head whilst listening to your binaural audio, you're not going to be able to take advantage of its motion sensor.
Henrik Oppermann, head of sound at virtual reality specialists Visualise, believes binaural sound is "absolutely necessary" to use within virtual reality, because it "makes up part of the natural experience".
"It is especially very important for storytelling, because sound plays a huge role in that," Oppermann said. "We create a sound sphere around you, and within that sound sphere, there is the binaural translation so you will be able to hear if something is below, above, behind or in front of you."
"It is becoming a regular expectation of the headset user that there is going to be a binaural sound field, but there is still a lot to be explored within virtual reality, and sound is going to be playing a huge role within that," he said.
As virtual reality mixes more and more with journalism, we may be seeing binaural sound used regularly within virtual reality news documentaries experiences, such as Hong Kong Unrest, but Brun notes that journalists may find binaural sound useful when immersing viewers in creative first-person radio packages.
Watch Rupert Brun speak about binaural sound at the Next Radio conference:
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