Sound check / normalization problem with matched versus uploaded tracks

Question

I am finding that matched tracks are playing MUCH louder than uploaded tracks on my iPod.  Before I started the match process, my library was normalized to an 89 dB reference level, which USED to be the audio engineering standard for recordings.  The AAC tracks that Apple has matched my tracks with seem to be as much as 10 dB above this -- the difference is painful.  To make matters worse, iTunes Match usually only matches portions of albums, so some of the tracks (the uploaded ones) are playing back at a reference of 89dB while the matched tracks are playing back at whatever Apple uses (my guess is @98-100 dB).  My understanding of the MP3 file format is that there is no benefit to ripping to a 100 dB level. It is not like the old days of analogue tape where you could improve the signal-to-noise-ratio by recording slightly 'hot.' In an MP3 file, there is normalization information stored in the file header. I do not know about AAC files.
I have turned 'sound check' on on my iPod, but it doesn't seem to make a difference.  Has anyone found a way to fix this issue short of renormalizing the entire library and then re-uploading verything to the Match service?  Needless to say, the original process of getting everything I owned to 89 dB was tedious in the first place and I don't want to have to redo that.  If I do need to redo everyhting, does anyone know what reference level Apple uses for its matched files?   

Answer 1

@ roebeet.  Thanks for telling me that 'Sound Check' does not work in iOS 5.  That is what I had found, but it's good to know it's not just me.  I talked to an Apple tech support guy and he seemed to know nothing about this.  He had me hard reset my iPod and then wrote it up.  He was quite nice about it, and suggested I send a recomendation email to Apple.
I downloaded a half dozen of Apple's matched AAC tracks from the iCloud and ran a volume check on them, and they seem to be using levels in the upper 90 dB range, so my guess that their tracks were a full 10 dB louder than my 89 dB tracks was confirmed.  What I've done to solve this is to remove all my uploaded MP3 tracks from the iCloud and from iTunes, renormalize them to 98 dB instead of 89 dB, then reimport them into iTunes and then reupload them to the iCloud.  It seems to be working so far.
You are right about some of Apple's stuff being clipped.  You don't need Audacity, either: digital clipping sounds so very very ugly.  The Apple 256 kbs AAC version of 'Babe I'm Gonna Leave You' from Led Zepplin I is clipped.  There is no excuse for this.  It makes me wonder how to alter a file so that it won't be matched: my MP3 version of the song is fine.
Thanks again for your help.