Rene Herman wrote:
André Pouliot wrote:
Sorry to tell you but using 16 bit 44,1KHz sampling most person can
tell the difference you are already at twice the nyquist frequency
for what the ear can listen.
No, the Nyquist frequency is the highest frequency that can be fully
reconstructed from data sampled at a given rate, and is half that rate.
With a rate of 44100 therefore, 22050 is that highest frequency and this
is not very far above the the highest frequency a good, young, human ear
can hear. 44100 is about minimum for good quality, full spectrum audio
therefore.
In any case, sampling at 96 or 192K is not done to now be able to encode
48 or 96K signals, but due to the preconditions of Nyquist's theorem.
Nyquist only holds (the signal is only losslesly reconstructable) when
the signal is very strictly limited to half the sampling frequency. In
the analog domain though, there is no such thing as an infinitely steep
filter meaning you still can get aliasing efects from higher frequencies
that were present in the pre-adc signal.
The higher the sampling rate, the easier for a filter to filter out
frequencies that would alias into the audible band therefore. 96/192 is
not audiophile humbug or anything.
Regarding input:
Yes the higher the sample rate as a multiple of the maximum frequency of
interest the lower the required slope of the analog filter. The problem
is that the bit stream still contains unwanted high frequency noise that
needs to be removed from the final digital output at a lower sample
rate. But, perhaps it is better to have only one high order filter in
the system to be applied before the final output recording or to do this
in software. The down side is that you have a lot more data to deal with.
I also note that if you are going to have more bit depth that this is
going to require a steeper filter cutoff slope.
--
JRT
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