Musings, rantings, ravings, and ramblings. This blog is mostly for my own archival use, but I figured it would be more fun to make such things open for others to comment on and mock. The title has two meanings: TIL is short for 'today I learned,' as most people who see this well know already. The whole title taken as a whole also happens to be my update schedule. I won't try and do something every day, I would fail. I would not limit myself to one post a day, should I feel. I think that settles things for now, on with the show.
Today I learned the amount of PVC needed to be considered 'fearsome'.
The audio frequencies of 20hz or lower has been demonstrated to cause fear responses in people:
http://en.wikipedia.org/wiki/Infrasound
This handy calculator can give the lengths of resonators needed to produce given frequencies:
http://hyperphysics.phy-astr.gsu.edu/hbase/waves/opecol.html#c1
Take those together, an open-air column 10.1 meters (33 feet, 1.5 inches) long will nicely create a 17 Hz note. Now, that's a bit inconvenient if one wants to make one out of 10 foot PVC sections. With that in mind, a 30 foot open-air column will produce 18.8 Hz, also confirmed to induce uneasiness. This leaves us with the need to actually get a pressure wave going.
Wikipedia has the answer, as well as many other places. I like Wikipedia though, very succinct.
http://en.wikipedia.org/wiki/Flue_pipe
You may have noticed this is a bit stream of consciousness. That's probably going to be par, here. Building the pipe will be no problem, after a bit of experimentation. Incedentally, a bit of help there:
http://www.sci-experiments.com/organ_pipes/Organ_Pipes.html
We're still left with the problem of air flow. Others have tread this road before. Others more inclined or able to track down the numbers. Others, dare I say, perfectly willing to share their research.
http://www.rwgiangiulio.com/math/flowrate.htm
http://www.rwgiangiulio.com/math/wst.htm
This also gives some clues on the construction of the flue in the first place. Back to airflow: Before doing any math, looks to be on the order of 5 to 10 cfm. I can't find anything on human cfm for playing an instrument and I'm ready to call it a night.
