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Comment by lebuffon | Hacker News Reader

It's more involved than just left/right delay. We localize sound in the vertical direction and front and back as well.

This is accomplished by the delays created between direct into the ear sound and reflections off the outer ear folds.

These reflections create "comb" filters in the audio spectrum which we learn to associate with direction. Its remarkable.

A test to prove this was so was to fill the outer ear with plasticine and perform localization tests on subjects. They could not localize sound in that condition.

The early work as I recall was at the Heinrich Herz institute in the mid 1970s.

I am suspicious that part of what this article is reporting is due to phase cancellation effects causing similar filtration that people can hear as timbre change rather than actually detecting the time delay.

(Source: My recording engineering final paper)

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Now I really want some plasticine / modeling clay to attach to parts of my pinnae and experiment with my ability to localize sounds.

Have video games already emulated the spectral effects of sound direction for players using headphones, or even speaker systems with known spatial distribution? I can imagine modulating the sound coming from an in-game object to match its perceived source direction to its location relative to the player.

The problem is that each person's pinnae have a unique geometry, which makes the notches of the comb filter lie at different frequencies for everyone. As far as I know, there's no good way to determine this other than a direct measurement, which requires specialist equipment.

Creative (Soundblaster) now have a phone app that you can take a picture of your ear and it uses a machine learnt model to produce a somewhat better head related transform function based on it. It is an improvement on SBX and CMSS before it but its not perfect either.

Video games, VR, and other headphone systems do use generalized HRTFs for directional audio.

Edit: I'm currently working on a series of videos to explain sound direction and perception. Some of the code I wrote for my demos is or will be on GitHub.

I recently purchased a system from Dr Jeffery Thompson for sound healing. It creates custom binaural beats based on the body's stress response as monitored by heart rate variability). The system includes a pair of sophisticated 3D microphones that go over the ear with the pickups being located as close to the ear canal as possible. This allows them to record the sound as close as possible to what the ear hears. We use them to record the client singing their tone. It then gets disguised and wrapped back into the binaural beat so you are essentially singing to yourself. I'm eager to go out and record some natural sounds in 3D for use as background.

Link? I’m trying to picture the apparatus you’re describing but it’s not making sense. Are there headphones involved or is it just a wearable microphone?

Some of them do, yes. For example CS:GO has an HRTF model that does this. It has variability though because each one's ear is slightly different, so these models are general and may work better or worse for different people.

I think this is called HRTF. The bad news is there are many of them and only a few work for each person.

This often results in being unable to tell front/back apart, frontal sounds perceived as coming from above, etc.

Some games have it, with good headphones and when it's implemented well it's great otherwise couldn't tell if it was on or off.

Even a "brand" for it THX Spatial Audio

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