@lostinseattle -
I was told that the pro audio world folks are the only group interested in such data. There is virtually no business there, and it is very difficult to break into and be profitable.
That low frequency signal is below 100 Hz I presume.
I think that they have some tests that were done by a tech at Harmon that there is spectrum graph looking at frequency versus noise floor of an amp. There were some interesting results, I'm told.