This leads to one of the most frequent arguments in the digital audio industry over whether it is even worth it to use the extra drive space and effort to record high sample rates when a) humans cannot hear it, b) the most popular playback mediums of CD and mp3 cannot replicate it, c) most microphones cannot capture it, and d) most instruments cannot even produce frequencies that high. There are even good arguments that feeding speakers higher frequencies than they are designed to handle will cause more distortion than if the frequency were limited in the first place.
There are a couple good uses for high sample rates, including “oversampling” for digital peak limiting, but for the most part, the listener will not notice any difference, and you should not be concerned with the quality of recordings sampled at 44.1kHz. They should sound the same as anything higher.
Bit Depth: The bit depth refers to the number of steps between the loudest and softest signals that can be recorded. At CD resolution of 16 bits there are exactly 65,536 steps (2^16). This translates to a “noise floor” of 96dB* . This was the resolution introduced early on in digital commercial recordings. Since then the recording bit depth has graduated from 20 bits of the ADAT machines to modern 24 bit resolution. This may not seem like a huge leap, after all it is only half again as many bits at CD quality, but trust the math: 24bit resolution allows 16,777,216 steps between the noise floor and the loudest possible signal and a theoretical noise floor of 144dB**.
Theoretical because it is far lower than the analog capabilities of even the highest quality mastering converter. This is 256 times the resolution of “CD quality”, and what this means is that the engineer can record at much lower volumes to preserve the dynamics of the signal, negating the need for destructive dynamic processing at the input. This is a very good thing for us on the production end, but after the signal has been manipulated for proper listening levels, 16bits is more than adequate. If you are wondering where .mp3 and other compressed formats come in, that is a topic for another article. For now be assured that even the simplest modern conversion machines can achieve phenomenal results. The real difference in a $10, and a $5000 converter lies in the quality of design and construction, and the transparency of the analog components. A good professional converter will have a noise floor of 114 to ~130 dB. Analog tapes and records have noise floor around 40dB for reference.
*Noise floor refers to the lowest point below digital clipping that a bit depth can achive. 96dB means 96 decibles below the loudest possible sound. At this point no audio information can be recorded, and gain applied to the signal will be filled with noise as a placeholder.
**Also note that in digital, 6dB equates to a doubling of perceived volume.