I can sort of understand records mimicing the sound of instruments, but voices are so unique, how did we ever figure out the exact carving of a piece of vinyl that when you drag a needle across it, you’ll get the same sound as x or y person’s voice exactly?
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Just to expand a little…As stated by others, the sound makes the carving. Sound is caused by motioning waves of air. These pressure changes would (originally) move a needle in turn causing the indents into the medium, wax or vinyl.
The original recording devices were a rudimentary microphone and cylinder creator rolled into one. You sang into the end of a giant gramophone which funnelled down into a small thin out-pipe (to amplify the air pressure) next to the needle that would push the grooves into the material. Eventually the process was recreated electronically, but the principle is the same. Grooves move the needle, the needle creates the impulse, the speaker turns the impulse into an identical pattern of air waves.
Additional:
Microphones and your ears work similarly in that the air motion vibrates a piece of film/skin that gets translated into electrical impulses as opposed to punching dents into vinyl.
Playback (as described above) is the opposite.
You can actually see this when you look at the woofer (the larger circle) of your speakers when playing something bassy. Because it is creating longer waves of air, the woofer movement is more noticeable to the naked eye.
Sound is vibrations, vibrations move stuff, like a needle or your eardrums. A vibrating needle moving over a rotating vinyl disk will create indentations, or scratches in the disk, thus recording the sound, be it instruments, voices or anything else that creates vibrations.
The sound is what carves the vinyl.
When recording, in the original technology, the sound vibrates a needle, which is dragged along the spinning disc to carve the grooves. When the record is put on a player, it spins and the needle is dragged across it. The needle is pushed along the ridges of the record, causing it to vibrate in exactly the same way as the one that carved it. That vibration goes up the needle as a sound, gets amplified, and there’s your recorded sound.
Sure, in theory, one could map exactly how a particular sound would cause the needle to move, and thus what exact shape of ridges would create that sound when it’s played, but it’s so complex to do something like that, it’d be easier to literally invent digital sound design and make the sound ypu want happen that way. Simpler to just tryst physics to take care of it for you. It’s just a matter of running the same physical process in reverse.
Side fact: it’s actually kind of a big deal in physics that most of the laws of physics run exactly the same backwards as they do forwards. There are a few specific things that don’t go like that, and that makes them really important in thermodynamics, relativity, quantum mechanics, etc.
The grooves aren’t carved by hand to produce that sound. They are directly carved *by* the sound they will eventually reproduce.
If you sing into a piece of paper you’ll notice it starts vibrating. Attach a needle to the piece of paper, place the needle onto a easy to scratch material and you have a way of recording your voice.
Obviously you’re gonna need something more sensitive to get anything near high quality audio, but that’s the principle behind it.
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