adding noise is the principle of dithering/noiseshaping
you can use it to lower low volume noise in an otherwise normal leveled setting to bring out the lowlevel parts more clearly when renderng to a lower bitlevel (f.i. 32fp to 16bit).
test : make a low level (-90 dB f.i.) sinewave (js:generator and record output
render it to 16bit with and/or without dithering and import all four
normalize all of them
Before play reduce the overall volume
undithered unnoiseshaped will be the ugliest. Lots of artefacts, you "hear" the steps.
dithered noiseshaped will be the best result , at -90 all will be covered with noise of course, but the sinewave is much more pleasing
with dither and without noiseshaping will be second best, but the noise come out too much (of cause , it's not shaped)
without dither with noiseshaping will be nearly as "ugly" as the one without all at a little lower volume (if cause, the noise is shaped and more earpleasing)
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