In an effort to reduce ambient noise in our symphony hall I've been asked to go in and measure the ambient noise levels of different fans, motors, vents, dimmers, etc at the audience listening position. The idea is that if we can identify items in the building that are disturbing the audience we can find a way to reduce the offending noise.
My current plan is to calibrate my mic to 94db with a calibrator and take a screenshot of an RTA/Spectrograph splitscreen for each fan or whatever as one of our engineers turns each one on. This will give me a graphic picture of both the sonic signature of the item under test, as well as a db reading as to how loud it really is at the listening position, great for passing on to the symphony board and the engineers along with a report.
Ideally I'd like to save a Spectrum trace for each one, and subtract it from a measurement of the room in its quietest state, essentially removing the room's ambient signature from the picture. Is there a way to do this? Is there any way to filter the results to ignore the room ambient?