Harmonics of a closed-closed tube

[abbeygeib]

I don't understand how to get n... if that doesn't make sense i can explain more... I have the length and velocity... from there i just don't understand what n even is or means...

 

[FredGarvin]

n is the mode or the multiple of the fundamental frequency. If you want the third harmonic, n=3.

 

[sophiecentaur]

It should really be referred to as the second (U)overtone(/U) for a physical resonator because the frequencies of overtones may not be exactly harmonically related. Look at the spec of Quartz crystals for use in oscillators and you'll see what I mean; It's all to do with 'end effect' and effective length of the oscillating object, in wavelengths. Having said this, for a closed-closed tube, the end effect will be v. small.

The fundamental frequency will be the frequency at which there is a half wavelength between the two ends - allowing a node at each end*. The first overtone will be when there is a node in the centre (i.e. at near twice the frequency) and the second will be when there are two nodes - asoasf.

* fundamental f =c/2x
where c is the speed of sound in the tube and x is the effective length