Understanding Resonant Heads

[C.M. Jones]

Crap re-rings just thought of that. They are there for structure but they will impact sustain I'd bet. Hmmmm that's a tough one-my knee jerk reaction it will increase sustain. But really it depends on shell thickness and size and wood type of re-rings. No matter what I bet it dry out a drum-it prevents deformation, but I bet the sustain will depend on design and wood type of re-ring. So a thin shell is naturally resonate the re-ring might impede motion of shell response so it appears to lose sustain-I think by design and hardness of wood you could overcome that to make it a resonator to return sustain.
The thicker shell is harder to activate so doesn't have a natural sustain, but what energy that does flow it's a lower fundamental long waves travel farther and I think the re-ring stiffness would focus the energy into the re-ring to act like a resonator. The thinner is more tricky my bet because the sustain comes from the shell and the re-ring might impede motion so it would appear to sound like a loss of sustain-but I also think you could design a re-ring that would act like a resonator so sustain maintained and likely this is what generally happens? The dryness likely comes from frequency shift to higher frequency because stiffness and stress increased at that point of re-ring I'd deduce. So generally a re-ring would increase sustain I'd bet but exceptions to rule-and perhaps we can explain why.

I'm no drum-maker, and I'm definitely not a physicist, but Pearl claims that the reinforcement rings in my walnut solid shell serve a two-fold purpose:

I. They preserve the shell's integrity.

II. They lend focus to the shell's tone.

I don't know the exact effect that the reinforcement rings have on sustain. My snare is pretty dry and makes a fairly succinct note, but those traits are also influenced by the shell's dimensions, wood type, thickness, heads, and tuning. As always, a black hole of speculation develops.

 

[basset52]

Thanks for posting CM. Nice clear and concise summary. It may not be new news, but I think it's always good to read info that refreshes our thinking or consolidates what we may have read before. I've saved it in my "Tuning Folder" on my PC.

 

[GetAgrippa]

The dryness makes perfect sense to me CM. Yeah I think build has a huge impact by so many factors-but I'm just thinking it through. That re-ring right at heads is like a stiff collar and makes sense it would influence drum head motions so "dry out" the heads with less overtones and a more focused sound.

Now I am thinking of overtones. The drum doesn't produce pure tones so overtones are obvious and just the nature of the beast-if you look at spectral analysis it's higher frequencies. That is all factors of two membranes equal. That isn't often the case as different tension lugs, different pitched heads or different weight heads changes how the membrane vibrates and interact-and overtones.
it's a profile of some pitch it's atuned and then generally higher frequency overtones.

Since it's a wave it has nodes where it rises and falls from baseline-the baseline crossing forms nodes. If the heads exactly tuned across lugs and both heads same tension you increase sustain -because the pressure waves pushing down from batter in sync with reso. Once you change the weight or tension(to reduce sustain) of either you create vibrating heads that are not in phase sync that we hear as overtones. Which before I've just assumed the two drum heads were same weight and same even tension across heads.But we know thinner shells often have more overtones too-likely because they resonate more. So heads source of sustain and overtones.

But the shell itself too-like thinner shells will be more resonant so prone to overtones. A drum shell is a circle so wave deflecting off wall should be focused central and though an interference to wave bouncing between heads-it all sounds in phase to us-clearer. A thick wall doesn't vibrate much so sound may sound more focused, but a thin wall is vibrating and because it's viscoelastic the sound waves will be hitting what acts like an irregular undulating surface (or a rough surface) to create phase differences in reflections. When a stress is appled to a vibrating viscoelastic surface-parts of wall will be stiffer and resistant and parts in phase or even supporting those frequencies -it's like you make it rough that reflect waves unfocused-. Because pressure wave will be hitting parts of shell more stiff and resistant and other more in phase re-enforcing so it will not focus sound in center and it will produce more overtones in the sound wave from resonance of shell too-because fundamental of thinner shell is higher it will be higher pitch overtones. So it will bend up and then decay pitch down in decay. I'm just ripping but it's like a thick shell focus sound in center to interference will be slight at one frequency but with reflected all over in a resonant wall it's like increasing certain frequencies and reducing others-we hear the differences as overtones in undulating frequencies. In nature you get echoes and reverberations from sound waves bouncing around as I recollect -it's gotta be similar so we hear it sustain or overtones.