<[EMAIL PROTECTED]> writes: > I've just spoken to my physicist friend, and he explained it like this. > When you have a beer bottle and blow into it, the pitch changes according > to how much beer ( air volume) is in the bottle.
Your physicist friend is right. And so am I. The resonance depends on both the volume of air and the area of the opening. (The resonant frequency is proportional to the square root of the area divided by the volume.) But unless you intend your guitars to function as variable volume beer reservoirs as well as instruments, the proper experimental procedure is, alas, to refrain from drinking the beer during the experiment and vary the opening. (I might add that nothing in Every Girl And Boy's Big Book of Experimental Physics prevents you from sampling the contents of the other five bottles of fine beverage in that six pack you bought just for this purpose.) >I just looked this up in my book here Which book ? Where ? > One needs a fixed solid air cavity with an opening. As one increases > the size of the opening it lowers the air space resonance, period!that is > science. Bob actually has it ass backwards! I'm not sure what to say to this other than to inquire about which controlled substances you may have ingested recently. A beer bottle is certainly a "fixed, solid air cavity with an opening" and as you close the opening the frequency of the air resonance goes down. Science doesn't operate by shouting or by writing "period!" at the end of a diatribe. It operates by experiment. Michael did you even bother to tear yourself away from your computer and actually try this? Lutenetters! Help Michael out here. Try this at home and report back. Take a wine or beer bottle. Fill it 2/3 full with water. (The change in pitch for a given change in area is bigger when the volume is smaller - patially filling it with water makes the effect easier to see (hear) but if you think this makes the results suspect leave the bottle empty). Blow across the bottle, note the pitch. Now cover half the opening with a finger. Try it again (it may take a bit of practice to get the note). Did the pitch go up or down? > I actually don't really get what Bob is talking about because he is not > using science and I have a hard time following him. May I suggest that this might be due to an insufficient background in basic science and a slightly overwrought emotional attachment to a dearly held, but incorrect idea? Seriously, I taught college physics for a number of years and as most professors will tell you, every once in a while you get the undergraduate equivalent of a "flat earther". A student will appear for office hours and be so frustrated and attached to their way of doing things, that they cannot see it when you point out where they have gone astray. At some point it becomes a waste of time for both of you. My way of dealing with it was to tell the the student "this is something you have to go home and think about quietly by yourself for awhile." Michael, I make the same suggestion to you. Take a break. Go to Lambert's. Have a nice dinner. Then take the wine bottle home and try the experiment. Get a copy of the _The Fundamentals of Musical Acoustics_ (Arthur Benade). Give it to your physicist friend along with _all_ the correspondence from this thread (not just your side of the story). Let him read the relevant chapters of the book and have him explain it to you. If the Taos library doesn't have the book this link: http://www.phys.unsw.edu.au/~jw/Helmholtz.html has a nice explanation of Helmholtz resonators as well as links to other pages on acoustics. > This really is not up for debate it is pure science, no matter how Bob > trys to sell it! I'm not selling anything. Regrettably I get no commissions from the Physicist's Union. If I did I would be trying the experiment with a higher class of beverage bottle. .......Bob ____________________________________________________________ ____________________________________________________________ Replies: (remove the "ZZZZ") Ekko Jennings: [EMAIL PROTECTED] Bob Clair: [EMAIL PROTECTED]
