Comparison between internal and external clappers

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Comparison between internal and external clappers

Postby TerryMcGee on Fri Mar 08, 2013 5:04 am

I thought people might be interested to hear this comparison between a 75 year old internal clapper and a more recently attached external clapper. Hopefully you will be able to hear the sound by clicking on this link:

http://www.mcgee-flutes.com/sounds/Comparison%20of%20Internal%20and%20External%20clappers.mp3

You'll hear three bongs from the internal clapper, followed by three from the external clapper. I think you'll agree, the difference is, um, "striking"!

Terry
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Re: Comparison between internal and external clappers

Postby JohnGouwens on Fri Mar 08, 2013 5:07 am

Wow! You'd have to be stone deaf not to hear that difference!
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Re: Comparison between internal and external clappers

Postby TerryMcGee on Fri Mar 08, 2013 5:19 am

And here's an FFT of the two sounds to compare the spectra:

Image

External clapper on the left, showing lots of high end partials, and internal clapper on the right, showing just our old favourite partials.

I should explain a bit for those not used to analysing sounds. Firstly, an FFT (Fast Fourier Transform) takes a waveform (recorded sound in this case) and converts it into the "frequency domain" rather than the "time domain". Also sometimes called a "Spectrum", because it's like splitting up a light beam into its composite colours. So we now see peaks representing the various partials. The fundamental is the peak on the left, just below 600Hz. The other partials are the peaks that stretch out from that towards the right. The higher a peak is, the louder it is in the mix of partials that comprise the sound.

Now, let's take the horizontal line at -48dB as a convenient loudness threshold. We'll say that peaks louder than that are significant, while those lower than that are not. On the right hand image (old clapper), we see 5 peaks above that. They are our old familiar friends, hum, nominal, tierce, octave and twelfth. (The quint and several others don't quite make it up to our line.) The bell is a D, so they are D5, D6, F6, D7 and A7, all concordant.

Now follow the same horizontal line in the left hand spectrum and you'll see the same, plus 5 other peaks, so we've doubled the number of partials that exceed our threshold. Further, if we carefully analyse these, we find they are not concordant (the poor old bell tuner is good, but he ain't God!). Some of the new partials immediately obvious are G7, C#8, D#8 and G8. Further, they fall in a part of the overall spectrum where our ears are very sensitive, so they punch well above their weight in terms of impact. That's why the external clapper sound was so bad. We've uncovered the bell-tuner's nightmare notes. It's like a really badly flattened internal clapper would produce, but maybe made worse by poor location and too light.

Terry
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Re: Comparison between internal and external clappers

Postby FrancesNewell on Sun Mar 10, 2013 2:00 am

Wow, the internal clapper sounds beautiful in comparison to the external clapper.
I certainly think that too many overtones make it impossible to hear clean, lyrical lines and effective harmonies.
Do you think that, as a group, the external clappers in this world will produce too many overtones?
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Re: Comparison between internal and external clappers

Postby JohnGouwens on Sun Mar 10, 2013 5:37 am

Not always. It can be done better. I would wonder if those particular external clappers are worn rather flat. Still, internal clappers can get off the bell much more readily. The effect is inevitably better.
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Re: Comparison between internal and external clappers

Postby TerryMcGee on Sun Mar 10, 2013 11:23 am

FrancesNewell wrote:Wow, the internal clapper sounds beautiful in comparison to the external clapper.
I certainly think that too many overtones make it impossible to hear clean, lyrical lines and effective harmonies.
Do you think that, as a group, the external clappers in this world will produce too many overtones?


I don't know, Frances, I haven't had that much experience with external clappers. I think they probably have to be heavier than internal clappers to produce a good result, and I suspect these ones aren't. These ones are also an odd shape - essentially cylindrical, although with chamfered ends. It would seem to me that a cylinder, lying horizontal across the bell, doesn't have to wear much before the strike point gets quite wide. But I haven't investigated it, and hope not to have to!

I think there might be other complicating factors too. A decorative bead running around the bottom outside of the bell probably prevented the clapper from being mounted in the best location. I'm also puzzled by the material of the clapper, which is grey but very fine, and welded to its shaft. It gives the impression of being very hard, but again I haven't investigated. What prompted me to post this here is to illustrate that a bell is no better than its clapper allows it to be. It really is analogous to the violin - many fiddle players have observed that a good fiddle cannot be played with a bad bow.

You are right on about the effect of the excess of overtones. You'll listened to one bell in isolation. Imagine a four note chord made up of four bells like this, with all their already clashing partials finding new partials to clash with. Ghastly!

This message has been brought to you by the Clapper Appreciation Society. Remember to thank a clapper today.....

Terry
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Re: Comparison between internal and external clappers

Postby Gideon Bodden on Sun Mar 10, 2013 2:16 pm

I'm sorry, but I find this a little bit silly. Comparing an obviously heavy clapper, with probably rust and dirt on the surface and made of a probably soft metal, with an external striker that is probably A LOT lighter than the clapper and which strikes at a worn and hardened strike spot.. The difference in sound on the recording is interesting, but has hardly anything to do with internal or external striking of the bell. This can be misleading.
By the way, I find both sounds on the recording substandard. The sound with the oversized (?) clapper is dull and empty, and lacks articulation, the 12th and double octave are way too much muffled. The sound with the external striker is better, in the way that there is a good clearness and you hear what this bell has to offer, there is a great movement in the sound, and especially when listened to from a distance, this is a more musical type of sound. The downside is that this sound may be a little too thin and doesn't leave room for much dynamics.
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Re: Comparison between internal and external clappers

Postby JohnGouwens on Sun Mar 10, 2013 4:10 pm

Well, much depends on one's taste. (Gideon and I have had discussions about this before.) I prefer clappers that have been rounded, and then "broken in" just a bit. I don't agree that the mellower internal clapper sound is "empty," though it would be brighter and clearer with a little wear. All that said, the simple physics of the matter are that an external clapper (assuming it actually contacts the sound bow perpendicularly to the surface) has gravity acting on it significantly. It's not impossible to make an external "drop hammer" to produce a good sound, but the far more likely, it will remain in contact with the bell longer than desired - re-striking or somewhat deadening parts of the sound. Gideon doesn't agree with the following comment, but I'll say it anyway: if the external clapper either re-strikes or damps the bell at the sound bow, it is in a position, potentially, to suppress the hum tone, minor tierce, and nominal, therefore creating by default more emphasis on the quint, as well as many unruly partials that aren't tuned (major tenth, two elevenths). Now, whether that is borne out by the graph I don't know, and I'd be interested in an analysis of it. The perhaps too-gentle sound of the internal clapper is surely more musically useful. the presence of G7 an G8 shows that elevenths are more pronounced than with the internal bell. You know, another big factor is how high up on the bell each clapper or hammer is striking the bell. That can make an immense difference. The undesirability of that particular external hammer arrangement is beyond dispute.
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Re: Comparison between internal and external clappers

Postby Gideon Bodden on Sun Mar 10, 2013 4:19 pm

We are hearing a clapper staying in touch with the bell longer, and thereby damping especially higher partials, so that emphasis is on the lower tones. And we are hearing an external striker that touches the bell for a much shorter time, allowing also the higher partials of this bell to sound. Exactly the opposite of what John suggests.
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Re: Comparison between internal and external clappers

Postby JohnGouwens on Sun Mar 10, 2013 4:58 pm

Well, we don't know for sure HOW it happens, but we agree on the effect. I don't agree that the internal clapper is going to contact the bell for a longer time than a drop-hammer. No way! The condition of the hammer (worn) as opposed to the internal clapper (more rounded, probably) is likely to be a bigger variable. This sort of issue (the tendency of a drop hammer to produce a more harsh tone) is part of why I stick to my theory about it. I'd be very interested to see what a disinterested party (neither Gideon or I would qualify) would come up with through a careful scientific study.
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