Comparison between internal and external clappers

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Re: Comparison between internal and external clappers

Postby JohnGouwens on Tue Mar 12, 2013 6:02 pm

Thanks, Gideon. All this is certainly interesting. I get the impression that Terry may have some interest in pursuing some study of some of this later on. Joey Brink (a physics grad student from Yale who is also a carillonneur - spent last year at Mechelen) has now subscribed to this section of the forum. We may hear from him at some point also.

As a practical matter, I know what I hear before and after re-voicing a clapper, so I'm firm on what happens to what we hear. I'm interested in understanding what is really happening as well as possible. I'm certainly surprised that the mellower sound of a re-shaped clapper comes from a longer contact with the bell, particularly in light of the fact that I can cause a bell note to die away more quickly with a snappy "staccato" touch. I would love to see somebody do a study of how and why that happens!! My theory there has long been that the bell is somewhat damped in the staccato case by the increased vibration (and consequent shortening) of the down wires.

Now Gideon might have some interesting insights on this matter. In some carillons, he has replaced the down wires with a much heavier wire grade, and used rigid couplings between sections of wire, rather than connecting loops. All of that would certainly reduce the play that a staccato touch imposes. He has found that that change causes the trebles to ring longer (which aligns with my theory). I played a couple of those carillons last summer, but honestly couldn't say whether I could make that "staccato/legato" difference on them or not. (Dealing with not-so-familiar carillons in recital was keeping me busy!) So, Gideon, I ask you, can you still make that sort of difference by touch on carillons using the more rigid vertical connections?

It is therefore rather interesting - and surprising - that the longer contact of a just-voiced clapper makes the bell ring longer, but the longer contact of vibrating transmission parts makes the sound ring for a shorter period. There is some food for thought - and study - in all that. I am no physicist, so I'm content to offer plausible theories from the sidelines, watching with much interest what the more scientific among you can determine.
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Re: Comparison between internal and external clappers

Postby TerryMcGee on Wed Mar 13, 2013 4:01 am

JohnGouwens wrote:It is therefore rather interesting - and surprising - that the longer contact of a just-voiced clapper makes the bell ring longer, but the longer contact of vibrating transmission parts makes the sound ring for a shorter period. There is some food for thought - and study - in all that. I am no physicist, so I'm content to offer plausible theories from the sidelines, watching with much interest what the more scientific among you can determine.


I wonder if thinking along these lines might help?

When the nicely rounded clapper spends a longer time in contact with the bell, it is transferring most of its energy into the bell, under the optimum conditions for smooth and efficient transfer of energy. The bell responds with a full and rich mix of the best-tuned partials, with a long decay.

When a flattened clapper slams into the bell and rebounds quickly, less energy is transferred, and the short burst of imparted energy favours the higher partials which die away quickly.

When, however, something other than the clapper and bell's natural time constants force a longer contact or cause them to recontact, the bell is damped and some of the energy it had received is robbed back out, causing a shorter decay and possibly distorted sound.

Again, I'm encouraging thinking in three cases, long, short and interfered with, rather than just long and short.

If anyone is in the position of being able to supply a recording where they think "interference" might be at work, we could see if we can find evidence. It would be great to determine a "fingerprint" for this case, as we have fingerprints for the first two. Perhaps for a start we should test a recording of a bell with the clapper firstly adjusted well, and then adjusted just a bit too tightly to induce a little audible damping. Although no-one is likely to play with it set like that, it might alert us to the fingerprint we might then look for when searching for other possible interfering agents.

I'd imagine the decay analysis should be particularly helpful here, but it's very easy for me to run any of these tests. Collecting the sounds is harder for me as I live about 150 miles (200K) from the nearest carillon!

Terry
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Re: Comparison between internal and external clappers

Postby JohnGouwens on Wed Mar 13, 2013 4:18 am

I think your explanation makes some sense. (We'll see if Gideon is convinced, or if Joey chimes in here.) There is absolutely no question that bells clunk badly if the turnbuckles are set too tightly. All carillonneurs have experienced that. (Some of the poorer of them don't know the difference, though.)
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Re: Comparison between internal and external clappers

Postby JohnGouwens on Wed Mar 13, 2013 4:20 am

It would be a relatively simple matter for me to record some sample notes, not only with maladjusted turnbuckles, but also with staccato touch. If you could analyze what is happening to the frequencies in both cases, that would indeed be very interesting.
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Re: Comparison between internal and external clappers

Postby TerryMcGee on Wed Mar 13, 2013 5:57 am

Let's do it!

Pick a bell you think it makes a good audible difference on - we'll want to be able to correlate the sounds and the analyses. Record a clean bell sound, then any other sounds you'd like to compare. Probably good to give me a couple of each in case I have any trouble with the analyses.

With the too-close adjustment, you might like to try more than one level - slightly too close and far too close, for example. It often helps in this sort of work to go too far in the first instance. That alerts us what to look for in more realistic cases.

Why not give me a couple of piano notes, average level notes and some fortes as well with the adjustment well set up. It will be interesting to see whether the fortes are simply louder, or also more complex (which is what we would hope).

Give plenty of time for the decay to fade out between samples - OK to use your pause button after a few seconds if you want to minimise the size of the recording. Also OK to edit for the same reasons, or to remove dud samples, but don't change the levels, as that might hide an important data point. Email as an attachment, or tell me where I can find it.

I haven't tried this, so no promises. But generally, if you can hear a difference, I should be able to find it.

If you can, a close recording is better than a distant recording which will be confused by reflections etc. People are better at ignoring reflections than microphones. But be careful not to overload the mic or recording system though, as that will confuse the analyses too. Perhaps record a couple of fortes first as a test to make sure they come out fine.

This should be fun. Or personally devastating!

And don't worry, I shall be on the lookout for the windup where you send me the same note digitally cloned 16 times, claiming it represents the full gamut of campanological possibilities!

Terry
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Re: Comparison between internal and external clappers

Postby Gideon Bodden on Wed Mar 13, 2013 9:03 am

We have already done such an experiment, back in 2006 (?), with Bill Hibbert producing graphs. Below two graphs showing the decay of the sound of a small Eijsbouts bell in the Amsterdam Munt Tower. First graph: turnbuckle set tightly, transmission (being both one directed crank and one rollerbar) greatly influencing the behavior of the clapper. Second graph: transmission practically detached, by blocking the baton to move down more than 3 millimeter, and banging on it, so that the clapper receives only an impulse and travels on its own towards the bell, the transmission staying behind in rest position.
bell2_stroke1.gif
bell2_stroke1.gif (5.13 KB) Viewed 10977 times

bell2_stroke2.gif
bell2_stroke2.gif (5.99 KB) Viewed 11366 times
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Re: Comparison between internal and external clappers

Postby TerryMcGee on Wed Mar 13, 2013 12:40 pm

Woah, that is certainly one fuddled bell! So there's no question about being able to see the results!

Did you do any other analyses in that set? I'd be interested to see a series with less tight adjuster settings, and one of your normal approach to setting the adjuster and playing the note.

What was the transmission chain in that measurement, Gideon?

Eg, adjuster tightly coupled to stiff wire, shackle, lever, roller bar, lever tightly coupled to stiff wire, shackle, clapper? (Amend as necessary).

If we do some measurements John, we should note the transmission chain too.

Terry
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Re: Comparison between internal and external clappers

Postby JohnGouwens on Wed Mar 13, 2013 12:49 pm

So, the over-tightened note is equal opportunity - shuts everything down together. Interesting to see both the slow waves in the hum and the smooth decay of the prime in the second graph. Is the behavior similar with Hemony bells? Does this actually teach us something about the behavior of the sound with a flat clapper? Pardon me if I'm not seeing where this is headed.
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Re: Comparison between internal and external clappers

Postby JohnGouwens on Wed Mar 13, 2013 1:18 pm

I would naturally use the Culver carillon, Gillett & Johnston, 1951. Transmission is roller-bar, and in the treble range, 19 of the top 28 bells go through a *second* roller-bar because of the way the upper bells are arranged. For sure the clapper behavior is encumbered by the transmission, but the trebles are low in the frame, so in general, we can get a lovely sonority out of the instrument. I don't have a flat clapper example at the moment, though perhaps we don't need that? I'm especially interested in the staccato/legato comparison. Specifically - does a "staccato" touch change the volume or proportions of the partials in contrast to a "legato" touch? Does that tell us anything about what is happening to the clapper to convey that distinction?

OK, so if I record those examples, is Terry and/or Gideon willing to analyze the resulting behavior, including decay?
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Re: Comparison between internal and external clappers

Postby TerryMcGee on Wed Mar 13, 2013 9:02 pm

I'm certainly up for doing the analyses, John.

Do you feel the second roller-bar makes a noticeable difference? If so, I guess we should really do a bell with and without the second roller bar. But maybe that's a follow up. In this business, you often find out other things you should have done, so a simple start makes sense.

I don't think we need the flat clapper, as we generally know what it does. If we get a good set of analyses, we might add that to it later when the clapper gets flattened, just to have a full set on the same bell.

With your adjustable, rotatable clapper, it would also be possible to do clapper too high, clapper too low, bell too tight, bell too loose. But let's not get carried away just yet!

Terry
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