This Instructable is splitted in two parts: theory and practice. If you are not interested in all the math and physics behind the project, you can jump directly to the practice section. If you want to know how to retrive all measurement, or even to customize your pipes, then proceed with next step.
Step 1: Theory
As I've aforementioned, you can skip this passage if you don't want (or need) to understand the physics beyond a pan flute.
OK, if you're reading those words you want to know more. I'm here for this!
A pan flute is a mere group of tubes with a closed end (called closed cylinder, even if one end is open). Each tube have a different length but, usually, the same diameter of all other tubes.
The length of the tube influence the pitch: longer tubes produce lower notes, shorter tubes produce higher notes.
The inner diameter of the tube influence the speed of blow needed to make the sound audible: smaller diameter means less blow, greater diameter means more blow.
Pretty simple, uh? No math, no strange formulas...
Now we need to find a precise relation between tube length and note pitch. Luckily, some physician (well, actually a lot of physician) already studied this matter creating and developing a branch of physics called acoustic. So we can "stole" their results to serve our scopes.
The formula we need is the one in the first pic. Here is the meaning of various symbols:
- L is the length of the tube
- v is the speed of sound
- f is the frequency
Fine. Now we need to determine which notes we want to produce, and their frequencies. I'm going to make a full octave pan flute, so I need 13 tubes: C, C#/Db, D, D#/Eb, E, F, F#/Gb, G, G#/Ab, A, A#/Bb, B and C again. Each tube will produce a note a semitone higher than the previous one and a semitone lower than the next one.
Since it's is too generic saying "I want to play an E", we must specify also the octave. In my case the first C is a C4 and the last C is a C5. This make the A an A4, with a frequency defined to be 440 Hz (modern concert pitch). From this we can determine all other frequencies using the second formula (second pic, obviously). The n is the number of semitones between the note we want and the A4. If the note is lower than n will be negative, if the note is higher it will be positive.