Comparison between internal and external clappers

Discussions on various technical aspects of carillon instruments and standards.

Moderator: JohnGouwens

Forum rules
1. This forum section is for discussions about keyboard and design standards, the merits of various types of action, the history of what various founders have done in the past, etc.

2. If you reply to a particular posting, please keep your reply on topic. Please also do not make multiple separate postings on the same subject.

Re: Comparison between internal and external clappers

Postby JohnGouwens on Mon Mar 11, 2013 4:51 pm

OK, do you have the recordings necessary to study and assess the decay time before and after voicing? I'm especially interested in that aspect of it. Taking a stab in the dark, it sounds as if:

1) Because the smaller contact area allows the clapper to contact the bell longer, the highest partials are suppressed somewhat, while the lower partials are more resilient to the longer contact. (This could arguably be attributed perhaps to the fact that the lower partials in fact have more of a "kick" to push the clapper back off the bell.)

2) The effect of clunking with flattened clappers has more to do with the behavior of upper partials. A flatter clapper allows the clapper to bounce off more quickly, and the high partials are far more prominent, but the high partials are also short-lived. The lower partials ring at least as long with a flattened clapper as a voiced one, but the more ephemeral nature of the higher partials makes overall effect of the bells sound shorter-ringing.

Make sense? By all means, please correct this if I'm off track here. I am certain about how the bells sound to a musician when the clappers are freshly-voiced. I cannot be so certain about why they do what they do. That's where I'd like some help with this.
JohnGouwens
 
Posts: 236
Joined: Tue Nov 27, 2012 4:20 pm

Re: Comparison between internal and external clappers

Postby JohnGouwens on Mon Mar 11, 2013 5:02 pm

Here's my best shot at summing up the effect. Comments, please:

With a carillon that is used once a week or more, strike spots on the clappers, especially of the most frequently-used notes, are going to wear flat over time. Worn clappers with too large a strike point tend to make the sound excessively bright and harsh, and on many carillons, they can make the treble bells sound “clunky” or short-ringing. Scientific study has shown that a flattened clapper actually contacts the bell for a shorter time, allowing the sometimes-unruly higher partials to be rather prominent. A more rounded clapper (either because it is new or because it has been turned or re-shaped) remains in contact with the bell longer, probably because the smaller contact area can deform a bit more before the vibration back from the bell pushes it off the bell. That in fact damps the higher partials. The lower partials tend to ring longer, so the net effect is that the sound we hear is not only mellower but seems to ring longer. The fact is that it only seems to ring longer because the shorter-lived higher partials have been suppressed, so the longer-ringing lower partials are more dominant. The behavior of the carillon transmission may also be a factor, particularly since most carillon transmissions introduce some “drag” on the movement, interfering with the clapper’s rebounding, and holding the clapper close to the bell too long. In any event, as clappers wear flat, we do know for certain what happens to the sound of the instrument!
JohnGouwens
 
Posts: 236
Joined: Tue Nov 27, 2012 4:20 pm

Re: Comparison between internal and external clappers

Postby JohnGouwens on Mon Mar 11, 2013 5:14 pm

This brings up a related point - and I'm not sure whether it is in conflict with the above or if there is a related explanation. On both the piano and the carillon, beginning a note with a quick "snap" of the wrist tends to create a sound that is shorter ringing, whereas beginning a note with more of a forward stroke creates a mellower-longer-ringing sound. This would warrant similar scientific study about clapper contact time to answer definitively, but your findings here somewhat challenge the theory I have long had about the matter. On a typical solid-wire transmission (and it's much worse on flexible cables), the wrist snap sets the down wires in particular into a vibration that effectively shortens their length. With the forward stroke, you can see that the wires don't dance around as much, and as a result aren't shortened by the activity. The thing is, the "staccato" touch doesn't make a mellower sound, and a really violent wrist snap can make a note quite dead indeed on many carillons.

My theory WAS that the vibration of the wires held the clappers to the bell wall longer and as a result somewhat damped the ongoing ringing of the bells. (This was just as true of a well-voiced carillon as one with rather flattened clappers.) The forward stroke spread out the acceleration more, leaving more wire length free, and allowing the clapper to bounce free and let the bell sound longer. The staccato sound isn't necessarily harsh, however, and can be used to great effect in soft passages. Might that theory still be correct? Some of this would vary depending on how the transmission is made.

I do know that a similar effect is very possible (and much used) on the piano, where I have long assumed that the hammer shank bent more with a sudden staccato touch, not recovering until it is holding to the string, thus damping the ringing a bit. I do not have scientific data to back up my theory, and I've in fact read contradictory reports from studies on the matter.

Thoughts on this, Gideon and Terry? Others?
JohnGouwens
 
Posts: 236
Joined: Tue Nov 27, 2012 4:20 pm

Re: Comparison between internal and external clappers

Postby TerryMcGee on Mon Mar 11, 2013 10:48 pm

JohnGouwens wrote:OK, do you have the recordings necessary to study and assess the decay time before and after voicing? I'm especially interested in that aspect of it. Taking a stab in the dark, it sounds as if:

1) Because the smaller contact area allows the clapper to contact the bell longer, the highest partials are suppressed somewhat, while the lower partials are more resilient to the longer contact. (This could arguably be attributed perhaps to the fact that the lower partials in fact have more of a "kick" to push the clapper back off the bell.)

2) The effect of clunking with flattened clappers has more to do with the behavior of upper partials. A flatter clapper allows the clapper to bounce off more quickly, and the high partials are far more prominent, but the high partials are also short-lived. The lower partials ring at least as long with a flattened clapper as a voiced one, but the more ephemeral nature of the higher partials makes overall effect of the bells sound shorter-ringing.

Make sense? By all means, please correct this if I'm off track here. I am certain about how the bells sound to a musician when the clappers are freshly-voiced. I cannot be so certain about why they do what they do. That's where I'd like some help with this.


I doubt if the recordings we made for the paper still exist. If so, they would be hard to find. Made on an analogue tape recorder belonging to a military establishment! (although a Nagra, so the best of machines!) And unfortunately, I just revoiced Canberra last November, so it will be a while before I do that again. If anyone is about to voice anything, they could send me a before and after recording.

We can probably learn a bit though from the current comparison, even though one clapper is outside. Ignoring all the low level partials, we find:

The Hum in the internal clapper is about twice as big as with the external, and shows the large beating we see in the tail of the waveform.
Primes are neglible
Tierce decays over about 1.3 sec (internal) and 0.95 sec (external)
Nominal decays over about 0.4 sec (internal) and has a curious three speed decay on the external, 0.1, then 0.45, then 0.8 seconds
SuperQuint doesn't show in internal, fairly prominent in external and decays over 0.55sec
Nominal octave not in internal, equal loudest partial in external, decays over 0.12 sec.

So we do see differing decay rates, even though it's the same bell. I imagine that energy is morphing from one partial to another. So you may not even be able to say "The lower partials ring at least as long with a flattened clapper as a voiced one" (see Tierce and Nominal decays above). Probably best to stick with your other statements, which I think are all fine.

Just one more observation. You may wish to clarify that you are not talking about the length of the long ring on at the end of the note (the tail), but the length of the splash that occurs after impact.
TerryMcGee
 
Posts: 99
Joined: Fri Jan 11, 2013 9:32 pm

Re: Comparison between internal and external clappers

Postby JohnGouwens on Mon Mar 11, 2013 10:56 pm

OK, so we don't have anything conclusive to say about why the sound is clunky with a flat clapper, though I would submit that the emphasis on higher, short-lived partials that "splash" for a short time would create the effect of a short-ringing bell. WIth the external vs internal, you did measure a louder hum tone, for instance. I take it that wasn't necessarily the case with the voiced clapper? Sorry, I am not good at gathering information from that report. Do we have any partials that are actually louder with a voiced clapper than they were with a flat one? (Of course, there is the variation in how hard one flicked the clapper in either case, so it isn't free of variables!)
JohnGouwens
 
Posts: 236
Joined: Tue Nov 27, 2012 4:20 pm

Re: Comparison between internal and external clappers

Postby JohnGouwens on Mon Mar 11, 2013 11:01 pm

I have revised my description (in the book) to the following, trying to be clear what is theory and what is known fact.

With a carillon that is used once a week or more, strike spots on the clappers, especially of the most frequently-used notes, are going to wear flat over time. Worn clappers with too large a strike point tend to make the sound excessively bright and harsh, and on many carillons, they can make the treble bells sound “clunky” or short-ringing. Scientific study has shown that a flattened clapper actually contacts the bell for a shorter time, allowing the sometimes-unruly higher partials to be rather prominent. A more rounded clapper (either because it is new or because it has been turned or re-shaped) remains in contact with the bell longer, probably because the smaller contact area can deform a bit more before the vibration back from the bell pushes it off the bell. That in fact damps the higher partials. The lower partials tend to ring longer, so the net effect is that the sound we hear is not only mellower but seems to ring longer. There hasn’t, so far as we know, been a scientific study that has evaluated why a more rounded clapper tends to create the effect of a longer-ringing bell. It may be, though, that it only seems to ring longer because the shorter-lived higher partials have been suppressed, so the longer-ringing lower partials are more dominant. The behavior of the carillon transmission may also be a factor, particularly since most carillon transmissions introduce some “drag” on the movement, interfering with the clapper’s rebounding, and holding the clapper close to the bell too long. In any event, as clappers wear flat, we do know for certain what happens to the sound of the instrument!

So, is this at least a reasonably accurate way to sum it up?
JohnGouwens
 
Posts: 236
Joined: Tue Nov 27, 2012 4:20 pm

Re: Comparison between internal and external clappers

Postby Gideon Bodden on Mon Mar 11, 2013 11:31 pm

A bell has no memory of what struck it and how. There is nothing a clapper can do to influence the way the bell sound decays. Gentlemen, if you don't make the full distinction between the effects of the bare clapper (hardness, mass, shape, suspension, speed etc.) on the sound of a bell, and the transmission influencing the behavior of the clapper and thereby of the sound of the bell, this whole discussion is totally in vain.
Gideon Bodden
 
Posts: 25
Joined: Sun Dec 23, 2012 12:52 am

Re: Comparison between internal and external clappers

Postby JohnGouwens on Mon Mar 11, 2013 11:41 pm

Gideon, I know what I hear before and after re-shaping the clapper. We know the behavior of the filed clapper SOUNDS longer-ringing. Certainly the bell has no "memory" of how it was struck. The question is, how does one account for the perception of a difference in decay time between a voiced clapper and an unvoiced one? The transmission isn't the variable here. We're talking about the same bell, on the same transmission, with the only difference being what has been done to the shape of the clapper.
JohnGouwens
 
Posts: 236
Joined: Tue Nov 27, 2012 4:20 pm

Re: Comparison between internal and external clappers

Postby Gideon Bodden on Tue Mar 12, 2013 12:09 am

JohnGouwens wrote:The question is, how does one account for the perception of a difference in decay time between a voiced clapper and an unvoiced one? The transmission isn't the variable here. We're talking about the same bell, on the same transmission, with the only difference being what has been done to the shape of the clapper.

If a certain way of striking the bell (in this case by using a clapper with a small strike spot) causes the hum note to sound with a greater volume, it will result in a longer ringing time than with the bell sounding with a softer hum note (for instance with a flat clapper). The ringing time of the bell is the ringing time of the hum note. If the hum starts out loudly, it will last longer.
A "clunky" sound, with the reverberation of partials being cut off in an unnatural way, is caused by the transmission, not by the clapper itself. A clapper, not under the influence of transmission, will make a bell sound loud, soft, bright or mellow. Not clunky.
Gideon Bodden
 
Posts: 25
Joined: Sun Dec 23, 2012 12:52 am

Re: Comparison between internal and external clappers

Postby JohnGouwens on Tue Mar 12, 2013 12:17 am

OK, and over here, all carillons have that issue. I did allow for that factor (transmission and drag) in my description. So you are stating that a more rounded clapper all things being equal, will in fact produce a louder (and therefore longer) hum note?
JohnGouwens
 
Posts: 236
Joined: Tue Nov 27, 2012 4:20 pm

PreviousNext

Return to Technical Discussions

Who is online

Users browsing this forum: No registered users and 1 guest

cron