Re: Yo! Can any Audiophile Geniuses Help Me out?

["Annie Hollinshead" <pagesangel@xxxxxxxxxxxxxx>]

My husband, who just happens to be an audio genius, says, "On music
signals the spectrum normally falls with increasing frequency so the
apparent fall off above 18k might just be a quirk of the coloured
display.  Without a more accurate graph you can't be sure.  If there
really is nothing above 18k, then the signal has probably been banned
limited by some previous processing.  This could just be an anti-alias
or anti-image filter used to band limit the signal to less than half
the sample rate to ensure correct operation  of a digital audio
system.  However, this would more normally be set at 20k.  Another
possibility is that the signal has been through some other processing
perhaps lossy encoding (mp3, aac, etc) and the encoder has chosen to
throw away the HF.

There are lots of other possibilities.  Without some idea of the
origin of the signal it is difficult to narrow it down.  By the way,
the loss of content above 18k is not very important because the
frequency discrimination of the ear at that frequency is very poor.
However, the processing that caused the removal of the content might
be quite audible."

And there you have it.  Nice to have a guy around that can answer
that!  Whew!  :)

On Wed, Dec 3, 2008 at 9:28 PM, Nathan Hevensone <nhevensone@xxxxxxxxx> wrote:
> What does it mean when a spectral analysis cuts off perfectly just above 18k?
>
> Like this:
> http://i382.photobucket.com/albums/oo263/losslessbootlegs101/specnib.jpg
>
>