Most peculiar, on my other computer all I got from cabbage was a blank screen. I thought he had joined the "less is more" crowd. I long on a different machine and find it's even better than that. He actually provides some interesting information.
On Wed, Apr 20, 2011 at 2:21 PM, <[email protected]> wrote: > Howard wrote: "I don't want to cut the bell on my N series 8D because > the > bell rings > forever. I suspect cutting it would destroy that. I remember one day > up in Boonsboro Walter Lawson was telling me how their bells ring > better than others. He whacked my N series 8D's bell with his finger, > and it probably still hasn't quit ringing. He was visibly shaken, and > immediately stopped telling me about that aspect of his bells' > superiority!" > > Dave W wrote > I have always had enormous respect for Walter and his work, but this is > one thing I could never understand. What does a ringing bell flare > mean? > What does the old "thunk test" prove? You could whack a steel mixing > bowl > and it work ring for a week. But would that bowl make a good horn > bell? And, > all other things being relatively equal, what would it tell you about a > flare that rung and rung versus one that seemed dead when you whacked > it? You > don't whack a horn to get the sound out. You vibrate the air column. > If a bell just kept ringing and ringing, would that not actually > interfere > with attacks, or with notes speaking, when playing runs? And if not, > why > not? > > I'm sure that a certain amount of "ringing" is probably good for a bell > flare to have, but isn't possible to have too much of a good thing? I > still haven't puzzled this out, and I sure would appreciate some > enlightenment. No one I've talked with about this can give me a > satisfactory > explanation, and I'd love to have one. > ************ > Cabbage says: > > Lawson did some studies of how horns sound with annealed and unannealed > flares. (These were published in the Journal of the Acoustical Society > of America some while ago.) An annealed flare is one which rings for a > while when you strike it; unannealed flares generally will not. > > The article indicates that the tone quality for the two kinds of bells > was most > different at high dynamic levels. The difference was a slight one: in > the annealed > flares, some of the higher frequency harmonics were enhanced by 3 dB or > so. The effect was > different for yellow brass bells compared to nickel silver bells. > > If the flexibility of the wall material matters, then there are two > influences it could have. The first is that the walls could flex > enough to produce > audible sound. The second is that the walls could flex enough to > change the > profile of the air column. > > I am aware of a study of metal organ pipes which demonstrated the > following: if an organ pipe oscillates strongly enough to make audible > sound from > the surface, it will also change its profile enough to shift in > frequency. > This is not desirable, so organ manufacturers make organ pipes stiff > enough to > prevent it. > > How does this relate to the horn? Here is some background. When sound > goes from your lips toward the bell, most of it reflects back to the > lips. > The low frequency parts tend to reflect in the narrow throat of the > bell; the > higher frequency parts of the sound reflect further out in the wider > part of > the bell. This means that the bell interacts most strongly with the > high > frequency harmonics in the sound. > > Some more background: as you play louder, the sound level of the > harmonics > increases. However, the increase of the higher frequency harmonics is > much greater than the increase of the low frequency harmonics. (If you > record a horn played quietly and play the recording with the volume > knob up, > it doesn't sound like a loud horn.) So the relative spectrum shifts, > enhancing > the higher frequency harmonics. > > Most of the tubing of your horn is too thick and has too small a radius > to oscillate very much. The situation is different for the bell: it is > much easier > to bend the bell than (say) the surface of the leadpipe. > > So what happens when you play loudly? The higher frequency parts of the > sound become more significant. Those are the parts of the sound that > interact with the bell. As they interact with the bell, the bell can > oscillate > and produce sound of its own. I speculate that this sound from the > bell can be audible and therefore contribute to the spectrum. Unlike > the > organ pipe, however, the frequency of the horn will not change, since > the playing frequency depends on how the low frequency parts of the > sound interact with > the narrow throat of the bell, which is not vibrating enough to change > the > profile of the instrument. > > Lawson studied the spectra of the sound produced by horns with annealed > and unannealed flares. But he did not determine how big the > oscillations > of the flares were, or whether those oscillations might produce audible > sound. > > Some while ago, I participated in a blind test of a horn played with > annealed > and unnanealed flares. (The flares had to be changed in a different > room: > it is easy to tell by the clanking noises whether someone is putting an > annealed or unnanealed flare on a horn.) I was able to distinguish the > two kinds of bells. The difference was slight, but apparent at loud > dynamic levels, when the tone quality of the annealed flares was a > little > less blatty. (I apologize for using such obscure scientific > terminology.) > > Still, I think the ringing of the bell is quite a minor aspect of a > horns sound. > If you play a loud note, then stop abruptly, do you hear the bell > ringing afterwards? > Probably not. > > Gotta go, > Cabbage > > > > _______________________________________________ > post: [email protected] > unsubscribe or set options at > https://pegasus.memphis.edu/cgi-bin/mailman/options/horn/bgross%40airmail.net > _______________________________________________ post: [email protected] unsubscribe or set options at https://pegasus.memphis.edu/cgi-bin/mailman/options/horn/archive%40jab.org
