Re: Complete cancellation of sound.
Herbert, Your point is well taken, I now concede to the cheese maker from NYC. Michael Thames www.ThamesClassicalGuitars.com - Original Message - From: Herbert Ward [EMAIL PROTECTED] To: lute@cs.dartmouth.edu Sent: Tuesday, April 05, 2005 9:24 AM Subject: Complete cancellation of sound. One might, a priori, suspect that two strings of a course would occasionally vibrate 180 degrees out of phase, cancel each other, and produce no sound. I wonder why this never happens in the real world. I understand that such cancellation is the basis of beats (eg, as used by piano tuners). But such beats are usually subtle, and never produce any- thing like complete silence. With two singers, one might formulate a hypothesis based on the different timbres and the different room positions. But such a hypothesis would not cover the case of strings in a course pair. To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
Re: Complete cancellation of sound.
The strings would have to be 180 degrees out of phase, but the waveforms even between two strings at the same is unlikely to ever be identical--different amplitudes for various harmonics, even not counting that one string might easily be plucked slightly harder than the other. But that's the facile answer. I was going to say that if you had a little demon suspended between the two strings the beats would come closer to complete cancellation of sound, and observers farther away wouldn't experience the cancellation, but no, we're not hearing the string's vibrations. My Soloette has strings, but is nearly inaudible. I suspect that a better place to look is the top plate. It's not the strings that we hear, but the vibration of the plate (influenced by the resonating cavity). I suppose that two strings could vibrate in such a way that the vibrations transmitted to the top plate would be cancelled, but it strikes me as intuitively highly improbable because of the asymmetries involved: if the two strings vibrated such that the vibrations cancelled on the left side of the plate, I don't think it's likely they'd cancel on the right side. The two strings would attach/sit on different places wrt the bracing. If I wanted to speculate even more, I'd wonder if there's any coupling between the strings that would disfavor having them stay 180 out of phase. But my coffee hasn't had its desired effect today. Tim B. At 10:24 AM 4/5/2005, you wrote: One might, a priori, suspect that two strings of a course would occasionally vibrate 180 degrees out of phase, cancel each other, and produce no sound. I wonder why this never happens in the real world. I understand that such cancellation is the basis of beats (eg, as used by piano tuners). But such beats are usually subtle, and never produce any- thing like complete silence. With two singers, one might formulate a hypothesis based on the different timbres and the different room positions. But such a hypothesis would not cover the case of strings in a course pair. To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
Re: Complete cancellation of sound.
i don't have the science to even attempt this but on the same principle, i once thought that a hand help loudspeaker (voice gun) could be attached to a multiple sound producing oscilator of some sort, aimed at any offending (LOUD!) noise and neutralize it at source. sort of a getto-buster instead of blaster. there's got to be a nobel in there somewhere ... - bill --- Herbert Ward [EMAIL PROTECTED] wrote: One might, a priori, suspect that two strings of a course would occasionally vibrate 180 degrees out of phase, cancel each other, and produce no sound. I wonder why this never happens in the real world. I understand that such cancellation is the basis of beats (eg, as used by piano tuners). But such beats are usually subtle, and never produce any- thing like complete silence. With two singers, one might formulate a hypothesis based on the different timbres and the different room positions. But such a hypothesis would not cover the case of strings in a course pair. To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html Send instant messages to your online friends http://uk.messenger.yahoo.com
Re: Complete cancellation of sound.
... different amplitudes for various harmonics ... Different phases too. If I wanted to speculate even more, I'd wonder if there's any coupling between the strings that would disfavor having them stay 180 out of phase. Interesting and plausible idea. ... But that's the facile answer. I suspect the correct answer relates to an interaction between (and superposition of) the three effects you mention. To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
Re: Complete cancellation of sound.
i don't have the science to even attempt this but on the same principle, i once thought that a hand help loudspeaker (voice gun) could be attached to a multiple sound producing oscilator of some sort, aimed at any offending (LOUD!) noise and neutralize it at source. There'd be so much asymmetric echoing and directionality that it wouldn't work. For example, red + blue = purple. But if a red light is on the north wall and a blue light is on the south wall, the total effect is easily distinguishable from light purple from its source(s). sort of a getto-buster instead of blaster. There is a commercial device which scans through the off codes for dozens of TV remotes, and will turn off many waiting room TVs surreptitiously. The brand name is TV be gone, TV-B-gone or somthing like that. I read retail is around $80. To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
