Accuracy of the theoretical formulas, which furnish the natural frequencies of air columns in the pipes having a discontinuous cross section, is tested by the experiment. A pressure-sensitive diaphragm having a high natural frequency was used to receive the pressure variation of air columns. And a record was obtained on a bromide paper by an optical method. For the periodic analysis, the N. Bernstein's method was used. And the experimental values of natural frequencies were in good agreement with the theoretical ones.