22. What "sample rate" and "bit depth" should I use when I am working with digital audio?
Always use the highest bit-depth and sample rate for best results, but be aware that higher bit depth and sample rates mean much larger files. Also, you will want to check what your sound card is capable of recording at. Higher quality and newer sound cards will support higher sample/bit rates. In RealBand, you can choose your audio file format in the Options | Preferences | Audio dialog. Versions 8 and higher support up to 24-bit, 96 KHz. Versions 7 and earlier only supported up to 16-bit, 44.1 KHz.
Bit depth: The more 'bits', the better the dynamic range (i.e. difference between quietest and loudest signal- or the number of 'discrete positions' of the amplitude.)
Sample Rate: The sample rate is measured in Hertz (Hz) which is the scientific way of saying "per second". 44.1K Hz means that there are 44,100 samples in one second of music.
The Nyquist Theory, states that the highest reproducible 'frequency' is exactly half of the sample-rate. In otherwords, if you record at the 44.1K rate, the highest audible 'frequency' you would be able to 'hear' upon playback would be 22K. (assuming your speakers were even capable of responding to 22k- i.e. very good tweeters) Since our hearing usually tops out at about 16K, this isn't much of an issue (sound processing issues aside). However, if/when you record at 22K (sample rate), the resulting highest frequency reproducible would be only 11K, which is similar to FM-radio fidelity.
There are many different opinions on how much of a difference recording at higher sampling rates and bit depths makes. In general though, you will get better results if you start with a very high-quality file and sample down from there if desired.
For more information, see our introduction to digital audio