Acoustic Tube resonance. (Not for general consumption).

Open

where *n* is a positive integer (1, 2, 3...) representing the resonance
mode, *L* is the length of the tube and *v* is the speed
of sound in air (which is approximately 344 meters per second at 20 °C and
at sea level).

where d is the diameter of the resonance tube. This equation compensates for the fact that the exact point at which a sound wave is reflecting at an open end is not perfectly at the end section of the tube, but a small distance outside the tube.

Closed

where "n" here is an odd number (1, 3, 5...). This type of tube produces only odd harmonics and has its fundamental frequency an octave lower than that of an open cylinder (that is, half the frequency).

A more accurate equation is given below:

http://mysite.verizon.net/cllsj/windchimes/length.htm

Hz. mm "

500 344 19.6

600 286 11.25

700 245 9.6

800 215 8.4

900 190 7.5

1000 172 6.77

1500 114 4.9

2000 86 3.3

3000 57 2.2

3500 49 1.9

4000 43 1.7

4500 38 1.5