[LAU] Rolling off high frequencies when mastering?

[Rob]

On Wednesday 21 April 2010 02:47 pm, micromoog wrote:
> > It is easy to understand that this correlation between phase and
> > correct amplitude also affects frequencies below half the
> > sampling-rate. Might be as
> > low as quarter of the sampling-rate, which in case of the CD is 11kHz.
> This is a pretty bold claim, and contradicts Nyquist and other
>  literature. Do you have a citation for the claim that frequencies "as
>  low as a quarter of the sampling-rate" are damaged by sampling?

While I consider this to be an academic discussion since I have high 
frequency hearing loss, it does seem to me that with a sample rate of 
44.1KHz, a 22.04KHz sine wave is indistinguishable from a 22.04KHz square 
wave despite being below the Nyquist frequency, and an 11025Hz sine wave is 
indistinguishable from an 11025Hz triangle wave.  I just fired up Audacity 
and generated a tone to verify this.

It seems like a pretty esoteric thing to care about, but if one does care 
about frequencies above 11KHz, I guess he really might need to consider 
sample rates higher than 44KHz.  The Nyquist frequency is the threshold 
above which tones can't be represented at all, not the threshold below 
which tones are represented with any kind of fidelity.  

Rob