 When the time units are seconds, the frequency is in formula_7, also known as Hertz.For a tube of length formula_8 with one end closed and the other end open the wavelength of the fundamental harmonic is formula_9, as indicated by the first two animations.Hence,

Therefore, using the relation
where formula_12 is the speed of the wave, we can find the fundamental frequency in terms of the speed of the wave and the length of the tube