"Anahata" wrote in message

Chris Hornbeck wrote:

The interesting bit lies
in the dither: information storage is actually increased
by adding noise

Prompted by the universal rule that you can't get
something for nothing, I have to doubt this.

Your doubts are well-founded. In fact, application of dither slightly
reduces information storage capacity. But, you don't give up something to
get nothing. Instead, you obtain a more listenable product and a more
generally useful product because quantization error is randomized (which you
say near the end of your post).

I think the
answer is that dither gets you more resolution at low
frequencies but less at high frequencies.

Not true in general, but certainly true in useful special cases.

Dither is often weighted or shaped to concentrate its energy at frequencies
that are outside the range where the ear is most sensitive. Then, your
statement is almost perfectly correct - resolution is increased at lower
frequencies at the cost of reduced resolution at the highest frequencies.
Since the ear is not so sensitive at the highest frequencies, this loss of
high frequency resolution is a more than acceptable trade-off.

It just so happens that's acoustically desirable because
it changes the quantization noise from something
signal-related to a constant white noise that is aurally
less distracting at the same level.

100% right, except that this is no happenstance - it is exactly per design.
OK, so "It just so happens" is a figure of speech. ;-)