why dithering is good for you...

http://en.wikipedia.org/wiki/Dither

The final version of audio that goes onto a compact disc contains only 16 bits per sample, but throughout the production process a greater number of bits are typically used to represent the sample. In the end, the digital data must be resampled to 16 bits for pressing onto a CD and distributing.

There are multiple ways in which one can resample the data to 16 bits. They can, for example, simply lop off the excess bits — called truncation. They can also round the excess bits to the nearest value. Each of these methods, however, results in predictable and determinable errors in the result.

Rather than predictably rounding up or down in a repeating pattern, what if we rounded up or down in a random pattern? If we came up with a way to randomly toggle our results between 4 and 5 so that 80% of the time it ended up on 5 then we would average 4.8 over the long run but would have random, unrepeating error in the result. This is done through dither.

We calculate a series of random numbers between 0 and .9 (ex: .6, .4, .5, .3, .7, etc.) and we add these random numbers to the results of our equation. Two times out of ten the result will truncate back to 4 (if 0 or .1 are added to 4.8) and the rest of the times it will truncate to 5, but each given situation has a random 20% chance of rounding to 4 or 80% chance of rounding to 5. Over the long haul this will result in results that average to 4.8 and a quantization error that is random — or noise.

This "noise" result is less offensive to the ear than the determinable distortion that would result otherwise.