how is digital sound created?

"In Space no one can hear you scream" - advertising blurb for the film Alien.

Digital devices generate the sound internally or sample the sound externally. Those electronic "frequencies" are converted to analog waveforms which can be amplified to drive a transducer (speaker) which moves the air.

The example you learned in school with the ruler on the desk was always flawed.

The sound isn’t from the contact of the thumb on the guitar string but the string vibrating back and forth. The question is how is that string energy recorded and brought back to life.

For that Wikipedia is your friend:

https://en.wikipedia.org/wiki/Sound_recording_and_reproduction

If stuff isn’t interacting with something to create a sound how are sounds created from nothing? I.e in the digital world? Music on an iPod or a beep from a computer? I have always wondered what the noise’s are and that come from computers when they are ’thinking’ or working - wtf’s going on there?

A good question and not often anyone asks so no big surprise no one knows. Heck I had to look it up a bit myself just to make sure and get it right.

With analog the electrical signal literally is an analog of the original sound. Air compresses a microphone membrane, which moves a magnet generating an electric current in a wire. This exact process is reversed at the other end. Digital is the same, only different, because instead of being an analog of the whole entire vibration digital breaks this down into discrete samples of the wave form.

What happens when playing this back is a string of bits corresponds to a particular voltage level. A whole bunch of them describes a stair-step of changing voltages. Exactly how this works is diagrammed out here: https://sciencing.com/analog-digital-converter-work-4968312.html

This gets very mathy very fast, which is why nobody talks about it, people being mathlexic and all. Best way to think of it, each bit or word represents the voltage taken at a certain point on the signal wave form. Playing it back the bits are reversed to generate a voltage based on the bits. This all happens very fast and the result is something some people call music.

Crappy cell phone and computer DACs have more of the stair-step distortion. Really good expensive DACs have a lot more quality parts and do a lot more processing trying to smooth the signal out by interpolating values in between the stair steps. It never works but like I said works good enough for some people to call it music.

Look up the Nyquist Theorem!