Re: Re: Damping valve casings : It works!!


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Posted by Mark in Ohio on January 17, 2001 at 18:07:24:

In Reply to: Re: Damping valve casings : It works!! posted by Henry on January 16, 2001 at 19:09:31:

Henry (and all readers),

You're on the right track, but I think many folks are confusing "damping" with what is actually a shift in resonance. If you add mass of similar properties (stiff metal to metal) then one is simply shifting the resonance of whatever the extra weight is attached to. the perceived "damping" effect occurs here because the increased total mass, in addition to causing a lower resonsnce, will now also require more energy to disturb it.

The original poster's experiment, however, involved blu-tak and such. This would have a somewhat different effect, in that the total mass (original parts + adhered damping stuff) will cause the frequency(ies) of resonance to be not just lowered, but also less pronounced than when the mass was stiff.

A glockenspiel mallet can strike a small bell, and create a very noticeable ring. That same mallet striking a massive church bell (using the same degree of force) produces little sound. Increased mass =lowered resonance that requres greater disturbance. (Like giant nuts soldered to valve caps).

Or you could ring the same small bell with the mallet, then coat the same bell with rubber & ring it--poor resonance. Like adding blu-tack, leather, etc. to your casings.

Hope this clarifies things a little. While alll the mods mentioned have an effect as folks describe, the means are fundamentally different. Both Bach and Schilke make some of the most sought after trumpets, even though their approaches are extremely different. The popular Bachs weigh lots more than Schilke's......

But both horns can be found in the hands of top players in the same orchestra!

FWIW,
Mark Mazak



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