This is a feature that has been noted in other alogs, such as 68679, but there is a recurring transient noise source from approximately 20-40 Hz. It appears as a broad peak or bumpy structure, usually starting at 20 Hz. The peaks appear to be spaced about 4 Hz apart. This structure has been visible in the past, but it appeared very frequently in DARM tonight. The broadness and prominence of the peaks vary; sometimes they are much sharper, and have more harmonics. I have been loosely keeping a list of times when it appears, and I attempted to run a bruco on one of those times but it didn't indicate any additional coherence from 20-40 Hz than normal.

I'm tagging DetChar and PEM to hopefully follow up more on this!