^^ True, but the cosmetic change in the graph might lead one to a different conclusion if we're not careful (i.e. not thinking about the practical outcome).
Edited by sdrucker - 10/27/13 at 11:03am
Thanks, Sanjay - appreciated. And, of course, for your help and advice. That goes for all the other guys who have helped and encouraged me along the way too of course.
I use a Mac (for viewing and messing with the data files - Windows for taking measurements (don;t ask). Can you do a screen cap (CMD-Shift-4) and upload the image in your reply. I am not sure what you mean. I am on Mavericks OS-X. Also did java update yesterday.
This is what I am seeing:
Well, my understanding of waterfall graphs is tenuous at best, so I would welcome a collective effort to improve our overall understanding on how to generate and interpret these graphs.
OK, here are four waterfalls, all the same underlying measurement, with the vertical axis lower limit varied by 5dB, from 60db down to 45dB. Focus on the 40-50Hz range.
As the lower limit is varied, the 40-50Hz area changes considerably, from a non-issue to a serious issue.
So, what are the waterfalls telling us? AFAIK, the key is the noise floor. If the noise floor were 60dB (unrealistically high), then the first waterfall tells us that we won't hear the ringing in the 40-50Hz range beyond ~400ms. If the noise floor were 50dB (more reasonable), then the ringing in the 40-50Hz range is still ~10dB above the noise floor at 450ms, i.e. still clearly audible. If the noise floor is 45dB, then the ringing in the 40-50Hz range is still ~15dB above the noise floor, very audible (and pretty bad).
Someone please tell me if I am on track, or totally off course.
BTW, and update on my ceiling fan, and the reflections issue it has been causing.
I replaced the fan with a Big Ass Fan. Yes, you read that correctly. Here is the web site: http://www.bigassfans.com/
The model I purchased is the "Haiku". It differs from the previous fan in that it has three blades (the old fan had five blades). This means that there is a stationary position for the fan blades that causes no reflection at the MLP. And, as I demonstrated earlier, when the fan blades are rotating, REW ETC measures no reflections.
Not a perfect solution, but a step in the right direction. And I can say now that I have a Big Ass Fan (priceless!), and that when the fan blades are rotating, they make a sound like "Twerk, Twerk, Twerk...".