Do I have to straighten you guys out again? Okay, listen up class.
If Sample Rate can be thought of as the horizontal resolution of the sign wave, then bit-depth can be thought of as the vertical resolution of the wave. Though, bit-depth does work slightly different than sample rate.
It defines the scale that is used to measure amplitude. More specifically it defines how many increments are on the vertical scale. NOT how many measurements are taken per second, but how many marks are on the ruler that we use.
Here’s an example.
If you used a scale with only 3 measuring marks on it, then the volume of each note recorded could only be set to one of those 3 values. The playback would have to make every note one of the following volumes; Loud, Medium, or Soft. (You only get three, so pick one.) However, if you increased the number to say 30, then there would be more positions to describe where the volume fell. The notes can be plotted to any of 30 different volumes. Again, it relates to the dot-to-dot story I told earlier.
8-bits, (poor), gives us a possible 256 marks on the ruler. 16-bit gives us 65,536 marks, (CD quality), and 24-bit gives us approximately 16.7 million marks.
Amplitude should be kept at high resolutions just as frequency should while recording and processing. Because when we process digital audio for effects, dynamics, EQ, or anything, the signal is subjected to intense mathematical formulas. We will no doubt lose some audio quality through the rounding of decimals. Higher rates are kept more accurate, lower rates are not. Once all processing is done, then we lower the rates back to industry standards.
So, always record as high as your hardware will allow.