The physics of drum tuning

[sketchtrack]

I once read that the best way to tune a drum is to first remove all the hardware, until it is just the shell, then hit it with a mallet, and match the frequency it resonates at with a tuning fork, then tune the top head the same frequency, and the bottom head slightly higher. This sounds good right? What would be the reason to tune the bottom head higher than the shell and top head?

 

[Andy Resnick]

I'm assuming you are referring to drums typically found on a trap kit (as opposed to tympani, etc).

I'm not sure there is a 'best way'. The choice of head is important. Some people like to tune the bottom head lower than the top, others like to tune the bottom head tighter, some tune to the same tone, others deliberately detune a couple of lugs to prevent ringing...

http://home.earthlink.net/~prof.sound/ [Broken]
http://www.peelerdrumcenter.com/tech_talk_drum_tuning.htm
http://www.drumsdatabase.com/tuning-drums.htm

It's a balance of the attack and the decay tones.

 

[sketchtrack]

I'm just trying to make sense of the whole picture, what is happening that makes the drum sound. First you have the resonant frequency of the drum shell, then you have the depth of the shell, and then you have the tightness of the top head and bottom head.

I did a project in high school where we made little drums out of pvc pipe, and we made a set to a scale by cutting them different lengths.

Would you say you could match the resonant frequency of the shell to the note achieved by the depth? Does that make sense?

How does the tightness of the head affect the actual note that the drum plays, and how does that interact with the depth and width?

It seams that a drum could be a few notes and tones at once because you have the depth, the resonating frequency, and the two heads. Wouldn't it be ideal to have everything on the drum ringing the same note?

 

[sketchtrack]

The first site you linked warned that sometimes you want to avoid very resonant drums because it can muddy the sound of the band. Maybe that is the reason to tune the bottom head slightly higher or lower than the resonant frequency of the shell? That way you don't have a drum which rings too much, but you have a drum with a clear and clean tone which rings evenly.

 

[Andy Resnick]

Right- exactly. There are a lot of variables that can be adjusted (depth, tension on each head, thickness of drum, material, internal damping, etc), and the total timbre of the drum is a complicated function of all those variables. Then there's all the mounting, which may affect the tone by loading the shell, preventing free resonant response.

For example, on my snare (5 1/2" deep, chrome, 14" diameter) I detune two bottom lugs, one on each end of the snare, to prevent "ringing" of the bottom head which would lead to uncontrolled buzzing sounds. For my toms, I tune the bottom higher than the top, to bring out a brighter sound on the decay. Some people prefer the opposite.

 

[sketchtrack]

If I were to take 5 drums the same diameter and make them different depths in order to go for a pentatonic scale, what formula would you use to figure the diameter to depth ratios?

 

[Andy Resnick]

Assuming everything is constant except for the lengths, you could most likely duplicate the lengths from chimes.

http://www.metalwebnews.com/howto/wchime/wchime.html

But you can also get a scale by tuning the heads- Terry Bozzio is the real innovator with that, AFAIK.

 

[dr_flam]

Dear all,

this topic is a bit old, however I joined the forum only now.

Since I'm not a physician (sorry, ) I was wondering if there is a way to determine quantitatively the presence of "frequency beats" in a recorded drum sound. I can hear clearly in my samples those which are affected by "frequency beats" but I would like to quantify this phenomenon. According to Worland (2010, Normal modes of a musical drumhead under non uniform tension, J. Acoust. Soc. Am.) "frequency beats" are caused by vibration mode splitting due to non-uniform head tunig.

best,

M.