Sourcing some of the items in the kits
for a slap tube that is to be played closed-open (ie the hand stays in contact with the end), there is one open-tube end-effect. So the effective length of the tube is
L + 0.6*r = L + 0.3*D
where L is the length and D the diameter.
4 times this length gives the wavelength and (speed of sound)/(wavelength) gives frequency.
Speed of sound is about 343 m/s and you can get the frequency from
So you need a length
L = (speed of sound/frequency)/4 - end effect
= (343 m/s / frequency)/4 - 0.3 D
If your pipe has ID 17 mm (like the electrical conduit we got from Bunnings), and you want middle C at 262 Hz
L = (343 m/s / 262)/4 - 0.3 (0.017 m)
= 323 mm.
C D E F G
323 289 256 241 214
A B C
191 169 159 mm
Because it's a percussion instrument, errors of a mm or so won't be a problem in tuning.
We have much more material about sound on
and musical sound on
Energy and Power Kit