A Rule Organ

By taping thirteen rulers to a desk, each with a different amount of overhang, we have a rudimentary musical (?!?!?!?) instrument. So, how much overhang is necessary, how do we do it, and why? Well...

If there's one piece of science that every kid knows, it's that twanging a ruler on the edge of the desk makes a noise, and by changing the amount of overhang will change the pitch. Give anyone a new ruler, and the first thing they'll do is twang it, to see how it sounds. This is an interesting fact of life.

To intellectualise this pastime we can say that we are discovering the relationship between wavelength and frequency (the longer the ruler overhang, the lowest the frequency of the note), and that we're listening for the timbre (pronounced tam-ber), which indicates the character of an individual sound, and is why a violin and piano sound different when playing the same note. This is less interesting fact of life.

Step 1: Prepare the rules

We start by determining the length of each overhang. By knowing how much is needed for the lowest note, C in our case, we can calculate the others mathematically. Finding the lowest note is done in typical school kid fashion by experimenting, unless you have a keyboard, guitar, or other musical instrument and an extra pair of hands, er, to hand.

You will notice that some lengths do not produce notes at all. Very short distances just produce a click, while very long ones make no sound at all. To make a complete octave, the overhang of the lowest note will need to be twice as long as the shortest (highest note), so if the rules you're using only make sounds between 5cm and 8cm you won't get a full octave.

TIP: Hold the rule to the desk as tightly as possible to produce the best audio fidelity (read: twang) possible.
How totally wonderful!
Bobby7173 years ago
I tried this with a couple of rulers and I think that the length is multiplied by 4 to be an octave lower.
I think it's proper that you used "make" to hold it down to the table.
rgreen103 years ago
which c does it start at?
mrmerino4 years ago
i would imagine you could maybe get some plywood or something, sandwich then inside, and make a ruler kalimba.
ewmr4 years ago
awesome, *cough*
red-king4 years ago
awesome.
MrLouque4 years ago
I just saw all the Make Magazines and started salavating!!
hustlngs6 years ago
this is pretty nice.. you have a lot of time on your hands but i could see this being very useful with a creative mind.. mad ups to you
agis686 years ago
These make magazines deserve better luck.....
sgphillips4517 years ago
Super thorough! I love that you describe all of the science behind everything!
gnargnar8 years ago
no video? you're killing me
7 years ago
go to the third step, the videos there
SteevAtBlueDust (author)  gnargnar8 years ago
8 years ago
So... Embed it in the instructable already! Then you'll get my "+". ;-)
SteevAtBlueDust (author)  clothbot8 years ago
Done! Anything else you want? A moon on a stick :) :) p.s. to others, uk.youtube domains don't work with embeded videos, you have to use the US site.
8 years ago
Nah, I'll settle for the "Make Rules!" you have pictured above.
jokojytok7 years ago
This is a phenomenal example of instruments of its type. I have only ever made a 13-note single octave, but my family and I are collecting different types of materials of differing lengths to accomplish something more permanent. I have found that metal rulers have more "brightness" in a piano sense, and more resonance overall, than the plastic shown here, but I am biased to metal, as I aspire to make the thing an "acoustic-magnetic" organ. Kudos on the clarity of design!
oskay8 years ago
I have always really enjoyed playing the ruler, although I play more of a "slide ruler" style-- fretless if you will. My favorite are the 1/2" wide steel machinists rules. They make a great sound.