[access-uk] Re: CDEX and normalising
- From: "Tristram Llewellyn" <tristram.llewellyn@xxxxxxxxxxxxxxxxxxx>
- To: <access-uk@xxxxxxxxxxxxx>
- Date: Mon, 10 Mar 2008 14:45:39 -0000
The term "normalisation" when used in its proper sense has nothing to do
with making music tracks apparantly have the same volume level. I am
not sure how CDEX implements the feature you speak of, I haven't used it
for a few years now.
The process of normalisation is used in order to optomise the apparant
level of audio to the maximum extent allowed by whatever bit depth 16 or
24bits of the digital audio path. What normalisation generally does is
look for the loudest parts of audio material and arrange things so that
those land at the top or near to the top of the 16bit audio range
without causing digital clipping. There are two types of normalisation
and one thus described is peak level normalisation which is perhaps the
most common. Normalisation is desirable because it helps maximise the
maximum dynamic range possible whilst reducing to a minium quantisation
errors at low level.
However the problem may be that you can normalise two tracks so they
peak at the same level but the apparant volume still seems to be
different because of the differences in the material which mean that the
average level of the sound of one of the tracks is higher. It is most
likely that the one with the higher average level will be determined by
the human listener as the loudest. This can also be made to happen
artificially during TV ad breaks and you find yourself wanting to turn
down the sound. In order to catch our attention commercials heavy heavy
audio compression applied to the sound to reduce the size of audio peaks
and turning up the makeup gain for the lower level signal so that the
average level becomes higher whilst the differences between the highest
level of sound and lowest is less, result, something that sounds louder
and more exciting.
In such cases as yours would would either need the help of software or
use your own ears to compare two or more audio programs and even out the
difference beween them as an average level because most likely the
normalisation process will not help. Also if you are sourcing from
commercial CDs this process will have already taken place. A breed of
individual in the audio industry known as a mastering engineer will be
making sure that all the tracks of an album sound like they fit together
and make sure the levels appear to the human listener to be roughly the
same. There are all sorts of other things they do to given an abum its
sound if that is the kind of project they are working on. I know iTunes
certainly a facility called sound check which evens out levels between
tracks in your music library but I don't it does it particularly well
come to think of it.
To add further fuel to the fire the human ear is not completely linear
therefore what a machine or software "hears" (I used the term advisedly
here) may not be what a human perceives. The vast majority of all the
acoustic energy in most pop music certainly is contained in the lower
end of the spectrum, thus a regeah track may sound about the same level
as something mush less bassy but the former still has more acoustic
energy in it whilst still sounding quieter and register a higher audio
level (as measured).
Hope this helps.
Regards.
Tristram Llewellyn
tristram.llewellyn@xxxxxxxxxxxxxxxxxxx
Technical Support
Sight and Sound Technology
-----Original Message-----
From: access-uk@xxxxxxxxxxxxx [mailto:access-uk@xxxxxxxxxxxxx] On Behalf
Of Andy Collins
Sent: Monday, March 10, 2008 11:15 AM
To: access-uk@xxxxxxxxxxxxx
Subject: [access-uk] CDEX and normalising
Hi all
Within CDEX settings, are tabs for normalisation, will this just make
all
tracks have the same volume, in other words, when ripping tracks, does
it
equalise the volume so that some tracks are not louder or quieter than
others? Am I right in thinking it doesn't affect the sound quality?
Thanks -
Andy
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