MECHANICS OF THE INNER EAR 



35 



We discussed above the result of a simple back and forth 



movement of the stirrup. Let us now do the same with a 



more complicated movement. Figure 11 



represents the new stirrup movement 



which we are going to study. This curve 



is approximately the one represented by the 



equation 



V = (1 — cos SttSO + (1 — cos 2-,r3t) ; 



which justifies us in saying that it represents physically the 



sum of two tones of the vibration ratio 2' : 3. Let us apply 



Analysis of the 

 combination 

 Sand 3 



Fig. II. 1 he combination 2 and 3. First characteristic phase 



the same graphic method to this case. We have first to trans- 

 plant the part of the curve from the first minimum to the fol- 

 lowing maximum, A to B, into figure 12'. Now, when the stirrup 

 reverses its motion, the parts of the partition near the windows 

 begin to be jerked up. Therefore, the curve from the maximum B 

 to the next minimum C has to be turned upside down and then 

 transplanted. The following part of the curve, from C to D, must 

 be transplanted in its original upright position, but placed on the 



