[access-uk] Re: CDEX and normalising
- From: "Andy Collins" <andy@xxxxxxxxxxxxxxxxxxx>
- To: <access-uk@xxxxxxxxxxxxx>
- Date: Mon, 10 Mar 2008 15:30:57 -0000
Tristram, I was hoping for a more thorough explanation than this :] I wish I
could get my head round some of this stuff the way some of you guys can.
Thanks for the explanation, I always try to achieve the best sound
[subjective I know] but because I have some high frequency deafness, I can't
trust my ears to know what others hear that I do not! -
Andy
----- Original Message -----
From: "Tristram Llewellyn" <tristram.llewellyn@xxxxxxxxxxxxxxxxxxx>
To: <access-uk@xxxxxxxxxxxxx>
Sent: Monday, March 10, 2008 2:45 PM
Subject: [access-uk] Re: CDEX and normalising
| 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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