Fluctuating noise with low organ notes on CD

[Petrus]

I recorded some Messiaen organ music played on a mid-size church organ with 32 foot bourdon in pedal. That would give a 16 Hz low note at best.

Recording was done at 24/96 with Sound Devices 722 and Sennheiser 8020 mics. Resampled down to 16/44.1 with 0.5 bit triangular dither with noise shaping using Audition 1.5. CD was made with CD Architect 5.2.

In places where the organ plays fairly quiet low notes with 16 and 32 flue ranks there is a strange fluctuating noise (starting around a few kHz and up) which appears from somewhere, separate from the blower noise and such. The modulating frequency is about 2-3 Hz and syncronizes in a way with the low note. It is possible that the same fluctuating noise is there in really loud sections, but is masked by the higher levels. The original recording is clean played from the recorder or DAW, the downsampled file is clean played either from recorder or DAW or from CD Architect timeline. It is there only on a burned CD-R.

I played the disks on 2 CD-players and one DVD player, all had the same fluctuating noise. What's going on?

[jordanstoner]

Pull the file off the CD and try a null test with the 44.1 stereo version from the DAW.

If it does not null completely, then you should try burning another disc, possibly from another burner and another app if possible.

[Petrus]

I looked at the files with Audition frequency analyzer. Original continuous concert file is fine. So are the separate files of each part of the composition. Both 2496 and downsampled and dithered 1644 versions.

But: when I recombine the files into one continuous file with Audition mixer and export this, the left channel gets extra fluctuating noise when low sustained notes are present. And only then.

I tried exporting 2496 WAV, same thing, AIFF, the same.

There is something wrong with the mixer export feature in Audition 1.5

As I need one second crossfades between tracks (need continuous backgroud hiss from organ blowers, but have to cut away 5-10 secs of extra pause and note change/registration changes) I try to do this in CD Arhitecht. There I can crossfade tracks quite easily, actually easier than in Auditon.

5 minutes later:

This new CD turned out perfect. Audition mixer is the culprit. I did not hear the noise played from DAW or CD Architect because the PC soundcard is quite noisy compared to CD or SD722 but the frequency analyzer showed something was wrong.

Is this a known bug in Audition?

[Thomas W. Bethe]

I have done a lot of organ recordings in my life but never run into the problems you are having. Could it be that there is a small offset in one channel? Could it be a phase problem in the recording? Could the 32 foot pipe box have a tremulant on it? Just some ideas....

[Petrus]

It did sound a bit like tremulant (by first thought). But it appears only when the lowest notes play, not before or after (and there is no tremulant on pedal). In the analyzer window the noise floor jumps up and down on one channel only about 25 dB in rythm with pedal beat frequency around 2 Hz.

And this was not heard in the church, it is not on the original file, the cut track files, ONLY on the file exported from Audition mixer.

Wrote a question to Adobe Audition 1.5 support forum, hope somebody still reads them.

Mics were 20 cm apart on Jecklin disk.

[Thomas W. Bethe]

Originally Posted by Petrus

It did sound a bit like tremulant (by first thought). But it appears only when the lowest notes play, not before or after (and there is no tremulant on pedal). In the analyzer window the noise floor jumps up and down on one channel only about 25 dB in rythm with pedal beat frequency around 2 Hz.

And this was not heard in the church, it is not on the original file, the cut track files, ONLY on the file exported from Audition mixer.

Wrote a question to Adobe Audition 1.5 support forum, hope somebody still reads them.

Mics were 20 cm apart on Jecklin disk.

I am thinking a problem with a small time offset that is only coming to light when you work in Audition. I have given up on Audition because we had so many problems with it and as of version 2.0 it will no longer work with our RME sound cards and the tech support people we very nice but NO help at all.