Volume leval on some albums seem to be adjusted down? (not ''soundcheck'' issue)

Hi, I'm having an issue with iTunes that is baffling me to say the least. I've noticed that under the ''file'' tab in ''get info'' it's showing that the volume decibel leval has been lowered in varying amounts from track to track. Showing as lowered anywhere from 1 - around 12 dB. Some albums remain totally unaffected by this and doesn't show anything next to ''volume'' like I said, only certain albums have all the tracks volume adjusted down. It doesn't matter what method I used to import my music, wether be it directly from itunes, or ripped from a cd. It seems to be totally random album to album.

I've searched and searched the net and can't see this issue coming up anywhere else and can't find any answers. I have the latest version of itunes and I have soundcheck disabled as i've always had. I've also checked all other settings and can't find anything. Anybody have an idea as to why this is happening? Many thanks in advance.