Topic: fluctuating noise in Audition 1.5 mixer export file

[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. One continuous take was split to tracks, extra pauses removed and then I recombined the tracks with Audition mixer window to one long file for CD (to have continuous ambience between tracks).

In places where the organ plays fairly quiet low notes with 16 and 32 flue ranks there is a strange fluctuating noise 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.

In Audition frequency analyzer window I can clearly see how the noise floor on left channel (only) shifts up about 20 dB when the low notes play. The level goes up and down in concert with the pedal beat frequences.

So it is the mixer which does this, but how and why? Only one channel, too?