28 KENNELLY AXD KUROKAWA. 



\\'d\e system set up in the tube, at a given frequency, appears to 

 correspond to the stationary electromagnetic wave system set up in a 

 certain equivalent alternating-current line conductor. The quanti- 

 tative relations in the two cases present remarkable analogies. 



(10) The plugging of the air tube at its distant end in the last men- 

 tioned case, corresponds to freeing the a-c. electric conductor at its 

 distant end. On the other hand, although the electric conductor 

 can be grounded at its distant end, no corresponding means appear 

 to be available for reducing to zero the acoustic impedance of the 

 open end of the tube. 



(11) Applying a telephone receiver to the ear of a listener roughly 

 doubled the total mechanic resistance at the receiver diaphragm, and 

 also increased its apparent elastic constant. 



(12) A telephone receiver may be tuned to maximum response or 

 vibratory displacement, over a certain range of impressed frequency, 

 by altering the length of an air column between the receiver and the 

 listener's ear. 



(13) The method of measuring acoustic impedance electrically 

 appears to be applicable to architectural acoustics. 



(14) Tubular musical instruments, such as flutes, e\'idently possess 

 acoustic impedances that are variable under manipulation, and that 

 are susceptible of measurement under the particular conditions 

 described. 



