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Comment by mjlm | Hacker News Reader

Localization of sound is primarily based on the time difference between the ears. Localization is also pretty precise, to within a few degrees under good conditions.

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Nit: time difference, phase difference, amplitude difference, and head related transfer function (HRTF) all are involved. Different methods for different frequency localisation.

There's this excellent (German?) for website that lets you play around and understand these via demos. I’ll see if I can find it.

Edit: found it, it’s https://www.audiocheck.net/audiotests_stereophonicsound.php

I think for stereo sound, media like music, TV, movies and video games use loudness difference instead of time difference to indicate location.

At least video games use way more complex models for that, AFAIK. It might be tricky to apply to mixes of recorded media, so loudness is commonly used there.

Unreal Engine, the only engine I'm more familiar with, implements VBAP which is just amplitude panning when played through loudspeakers for panning of 3D moving sources. It also allows Ambisonics recordings for ambient sound which is then decoded into 7.1.

For headphone based spatialization (binaral synthesis) usually virtual Ambisonics fed into HRTF convolution is used, which is not amplitude based, specially height is encoded using spectral filtering.

So loudspeakrs -> mostly amplitude based, headphones not amplitude based.

Which makes sense, there is only so much you can do with loudspeakers to affect the perceived location, you don't really know where the loudspeakers and the listener are located relative to each other.

Actually, the farther way the speakers are from the angles specified in the 7.1 format (see https://www.dolby.com/about/support/guide/speaker-setup-guid...) worse will be the localization accuracy. And if the the person is not sitting centered relative to the loudspeakers, but closer to one of the loudspeakers localization can completely collapse, and it will sound like the sound only comes from the closest loudspeaker.

In the case of gamers, they are usually centered relative to the loudspeakers, and usually the loudspeakers tend to be placed symmetrical to the computer screen, so the problem is not so bad.

For cinema viewers sitting in the cinema the problem is much worse, most of the audience is off center... That is why 7.1 has a center loudspeakers, the dialogue is sent directly there to make sure that at least the dialogue comes the right direction.

In music, simple panning works okay, but never exceeds the stereo base of a speaker arrangement. For truly immersive listener experience, audio engineers always employ timing differences and separate spectral treaments of stereo channels, HRTF being the cutting edge of that.

I believe Atmos as used in cinema rooms, is as far as I know amplitude based (VBAP probably), and it is impressive and immersive. Immersion depends more on the number and placement of loudspeakers. Some systems do use Ambisonics, which can encode time differences as well, at least from microphone recordings.

HRTF as used in binaural synthesis is for headphones only, not relevant here.

Tihs is true, but a high density of loudspeakers allows the use of Wave Field Synthesis which recreates a full physical sound field, where all 3 cues can be used.

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