Coke Bottle Resonance
The cavity resonance frequencies of a 0.5 liter glass coke bottle were recorded by blowing over the top of it and measuring the frequency using a microphone and a digital frequency counter.
C^{*} = constant for this experiment. 
Frequency  Volume 
Hz  cm^{3} 
355  100 
310  125 
280  150 
256  175 
239  200 
225  225 
212  250 
202  275 
193  300 
185  325 
178  350 
171  375 
165  400 
161  425 
156  450 
152  475 
146  500 
 When the resonant frequency is plotted as a function of the inverse square root of the volume, a straight line plot is obtained. This shows that the frequency is proportional to the inverse square root of volume.

The calculated frequency of a resonant cavity depends upon the speed of sound v. It also depends upon the square roots of three physical parameters: the area of the opening A, the volume of the cavity V, and the length of the opening port L. The quantity C^{*} indicated in the top graph includes the factors other than the volume which are held constant for these measurements.

Index
Wave concepts
Resonance concepts 