Monday, November 3, 2014

Mind Your Own Buzziness!

If you grope in the dark long enough, you will eventually stumble upon an interesting thing or two. 

I have made over 100 bass marimbas, I’d say, and I put buzzers on the tubes of every one. On the higher pitched instruments, I supply buzzers if the customer wants them. So you would think that I have buzzers all figured out by now, and I almost do, but I have been a sloooow learner. 

In the last few years I began to notice that drilling a hole in a tube and covering it with a piece of thin plastic, or any kind of material, does indeed create the intended buzz, but it also seems to diminish the strength of that fundamental, lowest tone that the bar produces. So for instance if you have a bass C bar, two octaves below middle C, played into a properly tuned tube you will hear a real nice boomy resonant loooow C frequency as the main sound. Now drill a hole in the tube and cover it with plastic and you introduce a host of higher frequencies that are the cool buzz sound. BUT you simultaneously diminish the low boomy resonance you heard originally. I guess that energy that you’ve used to create the buzziness has to come from SOMEWHERE. 

You can test this by playing any buzzing note, then muting the buzzer and hitting it again - if the tube is properly tuned, there’s a good chance you will hear your note blossom in it’s basement as the buzz diminishes, like turning your tone controls on an amp away from high and boosting the low.

More buzz, less rich resonance. This is not an argument for no buzz, just a note that sometimes good things come at a price. Anyone who’s fiddled with their buzzers knows that there is a wide range of possible sounds, so with buzzers, perhaps we are looking for some optimal combination of buzz and lowness and amongst all the possibilities I'm learning it may be possible to get your buzz on without all of your bottom falling out.

The Science Of It All(?)

So the other day teacher and multi-talented fellow David Reynolds Jr. brought a spectrograph iPad app to my shop and we played around with buzzers. We confirmed what I have been hearing for a long time:

picture 1
Picture 1 is an F bass bar with my standard chintzy shopping bag plastic tape over a 1 1/4” hole in the tube. The spectrograph shows us the harmonic profile of the resulting sound, with that lowest frequency (the highest mountain on the left) peaking at -32 db. and a whole bunch of higher frequencies that are the various overtones and buzzing in the -60db and -42db range. So far so good, sounds OK.

picture 2
Picture 2 is the same setup with the buzzer choked off (by my dirty fingers!). Check the profile now, with the buzzing removed. The low F frequency is boosted to -16db, and the various overtones etc. are hovering between maybe -66db and -48db.

Seems pretty clear in an amateur scientist kind of way then that introducing a buzzer on a bass tube is also diminishing the main low tone - David’s spectrograph seems to have confirmed what I’ve been hearing.

One reason I like to put some kind of adjustment on the buzzers, like those big rubber bands you see in the pictures, is so you can dial in how much of the buzzy bits you want. Back in picture 1, muting the buzzer just a tad with the bands really improved the buzziness and length of the tone - a 1 1/4” hole with such thin plastic covering dissipates the energy of the sound way too fast otherwise.

Many Variables, Many Sounds

As you might imagine, there is a whole world of buzzy variations to be heard, depending on how big the hole is, how thin or thick the material is, how taughtly you’ve taped… 

Frinstance: in this case we are working with that 1 1/4” hole as the given. What effect might other kinds of plastic have on the sound? The same hole covered with some super cheap packing tape, which is by far the easiest kind of buzzer to apply and manage and sounds great on higher pitched instruments, gave us a bass buzz that wasn’t all that strong or interesting compared to the super thin shopping bag plastic. It’s just too thick for that size hole, and with a smaller hole on a bass, it will hardly buzz at all. But now, Walt Hampton’s basses, made by John Eichmann (sp?) utilize packing tape with a great buzziness and I’d like to know exactly how big those holes are….. Of course there are different thickness of packing tape too - maybe Walt has found the world’s truly chintziest Dollar Store with the truly chintziest packing tape - again, more variables.

My Current State of the Blart

Here is my personal buzzer breakthrough to report, complete with more visual proof. Ready? Getting a really cool buzz in my basses (but not the higher pitched instruments) now involves the following simple steps, take note:

1. Travel to Portugal, Lisbon specifically.
2. Visit a Merlins hardware outlet, they are the Portuguese version of Home Depot.
3. Buy something. Make sure they put whatever you bought in one of their big plastic bags. Say "Obrigado".
4. Whatever you do with what you bought, save the bag, bring it home with you and use it for your buzzer material.

Something about that Merlins plastic… it is thicker than the usual US cheap shopping bag but seems very pliable too. Check out the profiles for my Merlin Style Portuguese Buzzers:

Picture 3
Picture 3, with the hole choked, pretty similar to the choked hole in Picture 2 as you might except. The buzzer is muted and you get the predictable stronger, isolated fundamental pitch peaking between -16db and -12db.

Picture 4
Picture 4, with uninhibited buzz. Look, we’ve only lost maybe 4 db on the fundamental, and all those buzzes and harmonics ranging between -54 and -24, are stronger across the board than the buzzing in Picture 1 produced by the thinner American shopping bag.

The visual evidence was sure apparent to our ears. I really like the liveliness of ALL the sound coming from this Portuguese plastic. Dang, I only brought one such bag with me from my recent visit there. Please do not ask me for any. But I will be on the lookout Stateside for this bag material.

Audiologists and acousticians and sound engineers may detect that I am no scientist. No doubt my terminology is poorly applied here, but hopefully you can appreciate how many variables are at work with these simple buzzers. If you and your students do some experimenting with those holes in your marimba tubes, in all ranges, you can control the variables to your sonic advantage. Bottom line for all your buzzing marimbas: Mind Your Own Buzziness!


  1. Tom

    That's really interesting. Did you experiment with hole location at all? I've been using a 1/2"-5/8" hole in the bottom of the plug and varying the buzz with different sized membranes. Newman cookie package wrap is my favorite I think. What app was that? I want to do some experimenting as well...

  2. HI Mark, that app is called "Analyzer". $15.

    I have tried so many different holes and materials and positions for holes over the years, I'm afraid I have not been very scientific in sorting through all the variables, especially when one forgets what one might have done specifically the last time, etc. Would be fun indeed to run this similar test with different size holes etc. no doubt some remaining "known unknowns" could be determined.