What Is Binaural Audio? A Complete Guide
Thanks to the rise of Virtual Reality and an increase in popularity of headphones, the century old format binaural audio is making a comeback like you wouldn’t believe. In the past 5 months, we’ve seen 4 major sound companies launch binaural recording headphones, the BBC release the first television episode (Dr. Who) in binaural, a feature film recorded entirely in binaural premier at Sundance Film Festival and musicians like Perfume Genius and Blake Mills release albums recored in binaural.
So what is Binaural Audio and how did it come about?
Binaural or Binaural 3D audio is audio captured identically to the way we hear the world. When audio is captured with a binaural microphone like the Hooke Verse (www.hookeaudio.com), it is capturing the exact location of every sound source and where it is in relation to the recordist upon capture. When you listen back to binaural audio recording on any 2 channel system (so any pair of speakers, any pair of headphones) you will feel like you are there in the moment, hearing it identically to the way the recordist did when they were capturing it. Hear for yourself (recommended with headphones on):
How Does Binaural Audio Work?
Binaural audio must be recorded with a binaural microphone. A binaural microphone consists of two omni directional microphones wherein one mic is positioned very precisely within each ear. When a microphone is placed within the pinnae of each ear, a recordist is capable of recording audio identically to the way they hear it.
Binaural Audio is NOT Stereo Audio
Binaural sound is not to be confused with conventional stereo sound. Stereo audio allows for localization to the left and right upon playback. With binaural, a listener can localize sound sources in front of them, behind them, above and below. Stereo does not factor in the natural ear spacing or “head shadow” of the head and ears. These things happen naturally as a person listens, generating their own ITDs (Interaural Time Differences) and ILDs (Interaural Level Differences). Stereo recording is not capable of capturing these ITDs and ILDs.
The History of Binaural Audio
It all started in 1881 when Clement Ader invented the first binaural audio system. Ader, who’d established the telephone network in Paris the year prior, installed an array of paired microphones at the edge of the stage of the Opera Garnier and transmitted the audio via two phone lines — one for each ear — to listeners located two miles away.
In 1940, Disney kicked off a sound revolution with Fantasia — the first commercial film released in stereo. “Fantasound” required a multi-speaker system for playback; problem was, movie theaters weren’t equipped for that yet. Fantasia got shown at thirteen custom-renovated venues across the U.S.. Installation of the equipment proved costly, making a wide release impossible. But, over the next three decades, stereo systems for both commercial and in-home use gradually became more affordable. Stereo overtook mono as the new standard, sidelining further experiments with binaural audio — at least for for the time being.
In the 1970s, home stereos and albums rose in popularity. More customers than ever were plugging gigantic headphones into the headphone jack, lying on the floor and listening to Pink Floyd or Zeppelin until the sun rose. With headphone popularity came a binaural popularity. German company Neumann unveiled the KU-80 — the first commercial head-based binaural recording system — at the 1972 International Radio and Television Exhibition in Berlin. Similar dummy heads developed by Sony, JVC, and Sennheiser soon followed, providing creators with the tool they needed to invent new ways of hearing. In 1978, Lou Reed employed a dummy head designed by German sound engineer Manfred Schunk to make Street Hassle — the first commercial pop album recorded in binaural audio — then followed that up with two more binaural albums, 1978’s Live: Take No Prisoners and 1979’s The Bells. (Read our roundup of The Best Albums Recorded in Binaural Audio.)
The problem was, these binaural microphones costed thousands of dollars, required a pretty steep learning curve and a bunch of other special equipment. They were really only reserved for professional use. And the companies weren’t interested in making a consumer option.
In the years to follow, we’d watch convenience rise over quality. Low quality (and mainly mono) digital music dominated our eardrums and advancements in bluetooth speakers took sound out of our ears and onto the coffee table via jamboxes. However, with the recent advancements in bluetooth headphone quality, the bluetooth codec, virtual reality and major companies like Samsung and Apple making a push towards Bluetooth, binaural audio and audio quality is back at the forefront of all things sound.
How does wind noise affect binaural recording?
Wind effects binaural recording the same way it effects standard microphones. Wind noise occurs during outdoor use when wind hits the microphone diaphragm directly. The stronger the directivity of a microphone, the more prone it is to pop and wind noise. An omnidirectional microphone is barely susceptible, whereas hypercardioid or figure-of-eight microphones are very sensitive to pop and wind effects. Pop and wind noise can be muffled effectively by a foam wind shield (pop shield).
Most binaural recording systems utilize omnidirectional microphones, which must be protected against wind noise despite their low susceptibility.
What file format is binaural sound recorded in?
A binaural recording is identical to a stereo audio file. Which means it’s a two track audio file. The two common types of audio are files are mono (one channel) and stereo (two channel). Ever heard a piece of music where you can detect specific instruments in different ears? That’s stereo. Ever heard a piece of music where every instrument is playing out of both ears? That’s mono, you can’t sense any directionality.
Either of these file types can be saved in whatever format you choose (.wav .mp3 .aiff etc.), which means a binaural recording too can be saved in whichever format you choose.
Can I play binaural sound on other speakers / headphones?
Once recorded, the binaural effect can be reproduced using any regular set of headphones or a dipole stereo. It does not work with mono playback, nor does it really work with loudspeakers as the acoustics of this arrangement distort the channel separation via natural crosstalk (an approximation can be obtained if the listening environment is carefully designed by employing expensive crosstalk cancellation equipment.) See Edgar Choueiri’s brilliant BACCH System.
If Binaural Sound is recorded wirelessly, is there latency?
That heavily depends on the transmission device one is using. Most bluetooth audio codecs experience a latency time of around 150ms. This is a problem as humans will begin to detect sound arriving later than an image at around 80ms. However, there are a few Bluetooth chips on the market that use a high quality Bluetooth audio codec which transmits at around 40ms.
When did binaural first start pairing with video?
If you’ve been fortunate enough to experience binaural sound, you’ve probably only experienced it on the listening end. It’s difficult to pair binaural sound with video because both formats must precisely reflect the perspective of the recordist in order to function properly. If you were to wear a pair of binaural mics and record with a video camera that is positioned 6 feet above your head, the resulting media would be inaccurate. We need to make sure we are capturing video the way we see it with our eyes in order for binaural recording + video to work together.