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How can you generate positional audio with a soundcard or some program for normal headphones? Virtual surround headphones have only one driver per ear, so they must process the information somehow to make it seem like it is coming from more than two speakers right? How are they able to do this?

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  • Do some search on binaural processing and HRTF, that's a way to produce surround sound on headphones.
    – audionuma
    Apr 18, 2016 at 20:17
  • I updated the question a bit to make it more clear what is being asked. As Olie pointed out, the term "surround sound" generally refers to using multiple speakers placed around the listener to simulate positional audio. What it seemed you are asking is how to produce positional audio from only two speakers worn on your ears.
    – AJ Henderson
    Apr 21, 2016 at 15:19

2 Answers 2

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There have been several commercial announcements and even a few released products which claim to offer "surround sound" via headphones. And there are several amateur, home-brew projects to do this as well. For example:

https://pcloadletter.co.uk/2011/04/05/5-1-channel-audio-through-headphones/

and

http://www.head-fi.org/t/447089/5-1-headphone-experience-foobar-configuration-for-all-stereo-music-files

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This is possible because of the way in which our brain actually processes positional information from audio. Each of our ears hears the pressure waves that impact it. They are not at all directional by themselves and just get raw pressure data. This information is processed by our brain to determine position based on patterns we develop based on the way sound is altered as it moves through and around our ears and head as well as the time delay in when it reaches each ear.

While filling a space with positional audio requires using multiple speakers (surround sound), it is possible to use headphones for virtual surround sound. The reason for this is actually fairly simple. When you are dealing with speakers located away from your head, the physiology of how your head impacts the sound gives each speaker source it's own positional data that would interfere with any artificially added positional data. That positional data is also going to vary based on where in the room you are in relation to the speaker, so it can't be corrected for (at least not for multiple people or listening positions).

With headphones however, we are piping sound directly in to the ear and don't have to worry about the normal physiological shaping of the sound. This allows us to add our own shaping to the sound to replicate the changes to the sound that would occur if our head was located in the actual positional sound field with actual audio sources.

In theory, this can actually be accomplished even more accurately than surround sound as surround sound still has a limited number of sources used for approximation. In practice however, it isn't that simple. There are a lot of variables to take in to account and the individual listener's head shape and ear shape and hearing characteristics all matter for a proper simulation. Some systems will actually take in to account some of these measures, however most consumer oriented approaches just use an "average" result that produces substantially sub-par results in many individuals.

As audionuma mentioned, binaural processing and HRTF (Head Related Transfer Function) are the two big types of processing being worked on now. It's an ongoing field of research and will continue to improve as hardware is better able to measure and adjust for it. There is some generally available tech, such as the upcoming Ossic X, that attempts to take some of these measures into account, but even it doesn't take all the measures that are used to make ideal signal processing in a lab setting.

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