Audio CD oddity

TorgoX on 2003-08-21T22:44:15

Dear All,

So I got the new Annie Lennox CD, Bare, and I'm merrily listening to it, and quite enjoying it.

Then one day I leave it on as I'm doing something else, and I don't notice when the last track ends, and the CD keeps going. There's some seconds of silence, and then a faint odd noise, and then it's the end of the CD and so the player stops. But I say, wait, what was that odd noise? I scan back and listen again, and it's really there -- a faint odd noise.

So I figure I might as well put my audio superpowers to work. I rip that track via a direct-to-digital method, and I examine the end of that last track. And yes, it's a faint odd noise. It's not a natural noise, and it's not musical. It looks like some kind of odd encoded data. It's not really part of the sound of the last track -- the FON (as I'll call the Faint Odd Noise) occurs after the low-lever white-noise noise floor of the CD has dropped out.

That is, there's the song, then it fades to "nothing" (actually faint white noise), and then that stops and there's several seconds of REAL audio nothing, namely samplepoints of straight 0's -- and then there's the FON, which consists of some evenly spaced short peaks, each on a background of straight audio 0's. And then more pure-0 samplepoints, and the end of the CD.

Look

Here, I put all of it in here. The .zip contains a .wav of the data, so you can listen. The other files are dumps of the data in various formats.

What is this stuff?!


cruft

jjohn on 2003-08-21T23:14:06

It's just cruft. There's no secret messages about Annie killing Dave Stewart or anything. That audio artifact could have been made in the CD-mastering stage. That's where the final mix of the album (that is, how Annie, her producer and engineers think the album should sound) is "enhanced" by record-label people with massive compression to make the album AS FUCKING LOUD AS POSSIBLE for car stereos and other noise polluters. It's very unlikely, but still possible, that the FON occurred after tracking the album in the studio. I doubt that any professional audio engineer would have shipped a DAT or whatever with that crap on it.

That fuzzy noise sounds a lot like bad grounding of some effect processor (like a compressor, although I can't be that specific). Obviously, it shouldn't have made it on to the CD. On closer listen, the FON sounds suspiciously digital. This suggests that the perhaps the conversion program that changes the mastering format to whatever format CDs use (which, recall, is a 16-bit, 44.1 khz wav file), had some issues with the noise floor. Math is hard, you know.