ACOUSTICAL lXVi:STrCiATlOy OF THi: JATANKSi: BAMr.Oo I'iri:. 



For ail example 



The variation of the sectional diameter of the pipe due to 

 knots, is at most 1/20 of the general diameter. For the fanda- 

 mental tones of the different positions, the effects of such a small 

 irregularity would be very small, as may be seen from the results 

 of experiments on the effects of the diaphragm. The effect, 

 however, increases when the irregularity becomes considerable in 

 comparison with the wave length, since the inclination of the 

 curves in Figs. 8, 9 and 10 becomes great with the decreasing 

 wave length. This probably accounts for the change of the 

 timbre due to the knots. 



A direct experiment on the effect of a small change of the 

 section was also made. Several glass tubes with equal lengths 

 of 23 cm., and equal general sections of 2.2 cm., except at a 

 place where they contracted or broadened by 1 or 2 mm., were 

 attached to the embouchure of a cylindrical organ pipe. They 

 were blown with a bellow under a constant pressure, which 

 was measured by a water manometer. The frequencies of the 

 different pipes were compared with a proper tuning fork by 

 counting the number of beats. Whether the note of a pipe was 

 higher or lower than that of the fork, could easily be decided 

 by slightly varying the pressure of the air ; if the increased 

 pressure decreases the number of the beats, the pitch of the 

 pipe is a little lower than that of the fork and incê verm. It 

 was found that the effect of such a small irregularity is very 



