In 8D audio, how is the audio able to sound like it’s behind or in front of you even though there are only left or right outputs?
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ELY5:
Our ears only have left and right *inputs.*
Our brains can tell where things come from because the shape of our head and our ears change how things sound before the waves hit our eardrum.
8D audio (and other similar effects) simply simulates what the shape of your head and ears do to the sound to make it sound like its coming from different directions.
In addition to typical stereo, your ears have a certain shape. When sound comes from various directions, it interacts in certain ways with those shapes and makes differences in the sound. You have been learning your whole life how to interpret these differences. These sound differences can be mimicked in the recording/playback to trick you into thinking it’s coming from a different direction.
I think you’re getting different answers because some people don’t know what 8D audio Is (I didn’t know about it until I saw this and looked up an example). The top comment is good, but it is answering a different question (it explains why we can detect if a sound is behind or in front of us in REAL LIFE scenarios, not with headphones in, like the “8D” audio).
With headphones on, as far as I’m aware, there’s no way you can detect if a sound is behind or in front of you, because you can’t turn your head (see the top comment for how this helps in real life).
Instead, it is more like an auditory illusion. Think of it like that optical illusion of the ballerina spinning: some people tend to see it spinning in one direction, others tend to see it spinning the other way. The same thing happens here. The sound is moving from side to side, but your brain wants to interpret it as moving in a circle, so sometimes it sounds like it’s in front of you, and other times behind you. But just like in the case with the ballerina, some people might think the sound is moving around you clockwise, and others might think it is going counter clockwise.
So while you might hear the sound as “in front” of you, someone else might hear it as “behind”
Edit: I should say this applies if you’re wearing “regular” headphones. If you have headphones that have speakers aimed at different parts of your ear, then it might be possible to simulate sounds being in front/behind, based on the spectral cues mentioned in the top comment by u/TorakMcLaren
Edit #2: I suppose an audio engineer could also simulate the spectral cues (ex. Add bass to sounds to make them sound behind you) but I don’t know how effective that would be, since the ability to turn your head is much more important for distinguishing where sounds come from.
In either case, these “8D” audios are almost certainly not doing the things I mentioned in my edits, so the explanation is probably just the auditory illusion
Very simple and maybe a bit inprecise ELI5-ish answer:
Sound changes on its way to your eardrums, as it hits obstacles etc on its way (head, ears, etc). Your brain then recognized how the sound has changed in order to determine where it came from.
By changing the sound beforehand, the directional “information” can be imitated, tricking your brain.
I studied acoustics at university, maybe i can help and hopefully not repeat anything that’s already been written
Many sounds you hear on a day to day basis, even in a musical sense, aren’t simple sine waves and tones, they’re a mix of many many different sounds that blend together to form a noise, this is usually called “resonant frequency”, which is why a guitar and a piano playing the same note at the same frequency sound different.
Things can affect this, like the wood used in the instrument that might absorb more frequencies or mute certain frequencies letting our brains figure out that we might be hearing similar sounds, but they’re slightly different. –
Its similar to when we hear sounds on certain sides of our bodies or from certain distances, the further away it is, the quieter and lower the sound is, or if we hear a noise on the left side of our body, from our right ear, it’s lost some of the volume or resonant frequencies because they weren’t long enough to “curve” or “stretch” around our heads to our ear. – Meaning it is possible for people who are deaf in 1 ear to determine the location of something based on the sound.
Using that same logic, if we study how audio sounds from 8 separate locations, we can edit audio that is being produced in a stereo left to right field to emulate how sound changes as it goes forwards, backwards, left and right, or up and down.
if you were to start from square 1 and try to edit all the minor frequencies and audio levels from each sound produced to make it seem like it’s coming from a certain angle or from a certain distance, it would take you an eternity – one project of mine was to recreate the sound of different instruments using only basic sine waves and manually drawing in the amplitude changes to emulate the attack and decay of sounds – it took forever and that was only a handful of notes.
or if you were to understand the logic behind it, and program a computer to adjust the audio of a sound within a 3D field to produce something in “8D”, then it would be quite easy.
I used to work on audio for surround sound in a 12.1 surround sound studio (4 speakers at 3 separate levels and 1 bass woofer) and it was relatively easy to create a 3 dimentional matrix and track audio through it to make it sound like it was moving around you when you played back. and this was 14 years ago. so today it wouldn’t be too difficult.
The term 8D is a marketing gimmick. It only uses left and right inputs because it is actually just stereo sound, and stereo only uses left and right.
Now, having said that, they can use digital sound mixing technology to manipulate the sound in ways that simply sticking two microphones in front of a band can’t. In a modern recording studio, every instrument and every singer is recorded separately. So, by adjusting the volume of each singer/instrument in the left and right channel, they can “position” each singer/instrument anywhere along the left/right dimension.
Now, here’s where the illusion starts. Imagine there is a singer in front of, and a bit to the left of you. Now, when she sings, you will hear her voice in your left ear a little bit before you hear it in your right ear. So far, this is what normal stereo does. Now, imagine that there is a wall to your left. What will you hear? You will hear the singer in your left ear, then the right, then you will hear the echo of the singer as the sound bounces off of the wall, first in your left ear, then your right.
Now imagine a violin player is standing beside the singer (to your right). The sound from the violin is going to hit your right ear first, then the left. In this case though, the sound bouncing off the wall is going to hit your left ear first, and then the right.
A computer can easily calculate all of those timings, working out the math of sound in order to place musicians anywhere. A computer can coordinate the sounds from multiple musicians (and computing the echos off multiple virtual walls) to make it seem like the band is circling around you. It’s basically the same ray tracing math that graphics cards do to compute an image and its reflections, except it’s done with sound instead of light.
However fancy it may be, it’s still just stereo, so all it needs is left and right.
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