Question about how analog audio recording works


Hello!

My wife and I are high and having a discussion about how sound is recorded on records. I have an, I think, more than average understand of how sound and recording/playback works so I was trying to explain how grooves on the record represent sound waves.

What we don't understand is how polyphony is physically represented. So I can see how a single sine can easily be represented on a record. But when you're talking several sounds at once, some on the same pitch some now, dozens of timbres happening all at once, how do we differentiate those sounds on a physical medium like vinyl, or how do we represent it digitally? Is it literally nothing more than 1s and 0s? That'd be sick

Anyway, I hope this makes sense. Thanks!

maynovent

Showing 1 response by zonkler

I’ll bite.

In any analog medium, waves are superimposed on each other.

For example, in water you could have small high frequency waves and large low frequency waves and what you would see would be big waves with multiple little waves on top of them.

For sound waves it is basically the same. Imagine a line with a bunch of small wiggles in it. Now imagine the whole line being bent (with those small wiggles still intact) into a much more gradual, large wave. Now you have the visual equivalent of two tones — a low tone represented by the broader up and down and a high tone represented by the smaller wiggles superimposed on the broad up and down.

If you looked closely at the groove of a record you would see this same thing. A mono record is easier to see it since it is a one dimensional wiggle. You would see a broad gradual wave in the groove, with a smaller, more closely spaced wiggle in it. The cartridge translates this to an electrical signal, which gets boosted in stages before it gets translated into driver motion, passes through the air as compression waves, and then translated back into motion at our ear drum. We then perceive this as two separate tones because we have hairs in our ears that are tuned to different frequencies, and those nerves send differentiated signals to our brain, which does some amazing magic to process those signals into the perception of hearing a two tone sound.