The Use of Binaural Audio
The term binaural audio is being used (and misused) a lot lately. Over the years, binaural has been applied to different aspects the audio industry. In this blog posting, there will be a definitions section and a discussion on the implications for virtual reality.
Recap from the last blog posting: headphones bypass the part of our auditory system that helps you localize sound, 3D sound can be broken into three elements: Sound source, Environment, and You, and Sonic VR is creating headphone solutions that put You back into the sound.
An Overview of Binaural Audio
Binaural, by itself, simply refers to two ears.
Yep, it’s that simple.
Binaural headphone has a speaker at each ear.
All headphones used for entertainment play sound at both ears. In this sense, almost all headphones are “binaural.” Some companies advertise this as a feature.
This is in contrast with some communication headsets, like those worn in customer call centers or by NFL coaches, which may only have a speaker at one ear.
Binaural recording are done with microphones in the ears of the listener or dummy head.
Binaural recordings are different from regular recordings because they are done at the listener’s location instead of at the sound source.
This is in contrast to most professionally recordings, which are done at, or with respect to, the sound source, then mixed and produced by an audio engineer. Recording at the source has better signal-to-noise, allows for better sound quality, and has greater flexibility in mixing.
Recording at the listener does capture more spatial information, but is specific to the head and ears that were used in the recording. This is important to know.
If you are listening to a binaural recording done with another’s head or with a dummy head, the sound quality and location accuracy to suffer. In fact, what is in-front of one listener can sound behind for another. Most of the time, the effect of binaural recording is a slightly spatial sound, but with very poor balance.
Binaural recordings are best played back through a simple set of headphones or earphones that have no spatial processing. They are not designed for loudspeaker playback. Binaural recording + loudspeakers = weird. Binaural recording + surround sound headphone = weird.
Binaural (rendering) takes source recordings and plays them back with spatial processing for a listener with two ears.
The problem is that the “listener” in these algorithms is a generic humanoid head, at best.
This has existed for a number of years with surround sound headphone technologies. It is being rebranded binaural audio, as of late.
For headphones, this adds some spatial information. However, as with binaural recordings, if the head and ears are not the same as for the listener, it doesn’t really work. The perceived locations and sound quality are off.
Binaural Audio And Virtual Reality
The fundamental shift with VR is from the third person perspective to the first person perspective. We all have extensive experience with the first person perspective, and our brains have expectations for sensory information. For audio, generic application of binaural processing or listening to binaural recordings with the wrong microphone locations will always fall short of reality.
There is a place for both types of audio: the high quality source recordings produced and mixed by professionals, and live recordings taken near the “listener,” like a binaural recording, but neither can be rendered by generic algorithms.
Stay tuned for next week when we discuss how to record and mix audio content for accurate spacial audio.
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