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/archive%40jab.org
