Hello all. I was hoping the community might be able to identify a sound for me. It is something present in many recordings of all sorts of things before, but there are too many factors to determine what it is except on a case-by-case basis. So I'm sure you've all heard it, obviously it's an excellent recording and an excellent show. But what I want to know about is this sound very close to the top of human hearing threshold, and it sounds almost like "air" or a "sound of silence", except it possesses an unpleasant pressure. I have taken some screen shots and will upload, so you can see what it looks like; it is the straight line at just below 16-KHz. If you listen to the concert, and follow the line causally, I think you will all be able to determine exactly which sound I mean. I am trying to remove this line/sound, but so far no avail without harmonic loss elsewhere; it would help a lot though if I knew what it was, as opposed to just trying to chop out something I didn't like. This line is present in many excellent vinyl rips, etc, i've seen The Line a million times, and loudness seems to be a common factor, but only in this Knebworth recording is is audibly conspicuous enough to bother me, and quite frankly it sort of ruins the show for me. One thing I find very curious is that the line is obviously present throughout the recording, but the sound goes away toward the end of the concert, like seven or eight songs before it ends. I have no idea why. There are times throughout the show that the sound dissipates momentarily, and sometimes it goes away in accordance to instruments being used, in a gating/ducking/replace-the-sound kind of way. this leads me to believe that it is a channel fader up on the board for something that is unutilized, so it's just an open empty channel. But like I said, there are quite simply too many factors, so I was hoping people could help me in this particular instance. Because it is a recording of a concert, it could be feedback, it could be quantization distortion, it could be the open channel, it could be phase, it could be the PAs and amps, like turned up so much you're just hearing them all being ON period... I'm pretty positive it has nothing to do with the tape, because like i said i've seen it in vinyl rips etc... but really in the end there are just too many factors. I don't expect anyone to necessarily know for a fact, unless like maybe if you were there yourself, or are yourself a musician who has lots of live-performance experience, but even if anyone wants to take a guess, please do; any and all input is appreciated. My question has no stupid answers, srsly even if you have zero knowledge of pro-audio it doesnt matter, just shout out whatever, you'll never know what magic words might help answer the question for me. thanks guys! i'm looking forward to your responses. peace for now. pics below. PS - i am including as a fifth picture a random vinyl rip spek as well, just so yall can see an example of The Line elsewhere than Knebworth. The vinyl rip is an excellent recording done on high-class gear, in fact that's where i've seen the image the most, which is why i think loudness can be a common factor; also, there is always like ONE rip out there that's better, and it never has the line, so that leads me to believe that at least in the case of vinyl ripping it's a gainstaging issue. anyhow thanks again, cheers.