Despite the name, 8D audio doesn't involve eight dimensions. It is a post-production effect created using and equalization.
: To simulate a real-world environment, a specific amount of reverb is added, making the song sound like it's being played in a large stadium or a hollow hall rather than directly in your ears. The Experience of "Fuel" in 8D Metallica - Fuel (8D SOUND)
: Kirk Hammett’s wah-heavy soloing benefits from the spatial depth, often feeling like it is soaring "above" the listener. Why It’s Popular Despite the name, 8D audio doesn't involve eight dimensions