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Comment by jakobegger | Hacker News Reader

I wonder how people play back those 3D recorded sounds?

If you want a 3D audio experience, it's possible to do that with just two microphones and a dummy head model [1]. Then you just play back the recording with earbuds. It's pretty fascinating that something so simple works, but you can only listen from the position where the recording was taken.

I guess if you record using one of those complicated mic arrays, it may be possible to simulate the effect of your pinnae in software, allowing you to move around in a virtual environment, and hear the 3D audio from different points?

[1]: https://en.m.wikipedia.org/wiki/Dummy_head_recording

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Yeah, you have to simulate the attenuation from different directions - HRTFs (head related transfer functions)[1] are used to do this. They're already supported by some games, and you have to use them for VR audio, since the user is in control of the camera position and angle.

[1] https://en.wikipedia.org/wiki/Head-related_transfer_function

Right, binaural is very good but it only works if you keep each ear in the same place. Ambisonics record the sound pressure from every direction so you can turn your head and still get directional sound. At least, assuming you have several speakers to recreate the sound field reasonably well. If you only have two speakers, the approximation will be kinda rough.

You could do it with headphones if you tracked the head motion and remapped the spatial signal through the HRTF in real time.

You set up a lot of speakers and a decent computer. Two decent computers if your room isn't ideal.

>Music Research Centre's Arthur Sykes Rymer Auditorium is equiped with a sixteen speaker Ambisonic rig. This rig cosists of four high speakers, eight horizontal speakers and four speakers below the audience in the air conditioning plenum duct, which was designed to allow for this. The rig is driven by a Firewire audio interface (Focusrite Saffire Pro) which can be accessed from computers positioned in the performance area via Firewire. This rig can do up to third order horizontal with first order height.

https://www.york.ac.uk/inst/mustech/3d_audio/ambisyrk.htm

Here's some more York uni ambisonics stuff - https://www.york.ac.uk/inst/mustech/3d_audio/ambis2.htm

The minimum number of speakers for a horizontal ambisonic setup is 4 but you need at least 6 to localize sound in a full sphere: https://en.wikipedia.org/wiki/Ambisonic_reproduction_systems...

I'm not sure if massive speaker array systems like BEAST (http://www.beast.bham.ac.uk/about/) use ambisonic diffusion techniques, I think part of the appeal of ambisonics is the relatively small number of speakers you need for full sphere spatialization.

(It's also interesting to see this subject pop up here. Maybe because Zoom is offering a consumer option now? I've heard good things about the octomic: http://www.core-sound.com/OctoMic/1.php )

Pink Floyd's (or, perhaps more correctly "Roger Waters'") "The Final Cut" made extensive use of the binaural recording technique (or, perhaps, more correctly "holophonics").

The best example on that album was the missile going through the "air" towards impact. A good demo of the technology.

"Pros And Cons Of Hitchhiking" is probably a better example, if not nearly as musically satisfying.

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