Notice that at any given point in time we have a certain amplitude, plus there are infinite points of time. This signal can be captured via a microphone and stored in something like a
gramophone record. But we want to store them digitally right? We no longer have gramophones. Or in other words, we need this signal to be discrete rather than continues in order for us to store it in a computer. So we have to sample this signal at a frequency. This raises a few questions:
- At what frequency we should sample our continues signal (sample rate)
- How many bits we should use for storing each sample, or rather what is the amplitude range we are willing to cover (bit depth)
p.s: Bit-rate is basically sample rate multiplied by bit depth
For the first question, the answer lies in
Nyquist–Shannon sampling theorem. Which states that to reconstruct a signal via samples, we have to at least sample at double the frequency of the original signal. This makes a lot of sense if we just look at visualization:
