6 KENNELLY AND KUROKAWA. 



g being assumed constant over the entire surface of the diaphragm. 

 This power may be expressed as 



T = l-iS abwatts (7) 



1 fs 



where ^' ^ o I •^"" ^^^ ^^^^- ^i"^^)' (S) 



or the ^'ecto^ mean ^'elocity square i- is the integrated mean value of 

 x^ over the entire surface. Under these conditions, the acoustic im- 

 pedance of the tube at the disk including both of its sides, will be 



z = . acoustic absohms Z (9) 



i 



The mean square ratio ( ^ ) = ( ^ ) of average to maximum central 



vl'o/ \-*"c 



velocity or amplitude has been called the mass factor ^ of the dia- 

 phragm denoted by —. 



Total Mechanic Impedance on a Diaphragm: When a telephone 

 diaphragm is set in vibration under an impressed vmf., due to a 

 simple harmonic alternating current in the coils, the maximum cyclic 

 velocity of the diaphragm over the poles depends upon the total 

 mechanic impedance to motion. The vector vmf. F may be taken as 

 proportional to the exciting current I rms. absamperes flowing through 

 the coils. ^ 



F = A I rms. dynes Z (10) 



Here A is the ^-ector force factor of the instrument, and ordinarily 

 has a slope (3°, of about —.30°, so that the vmf. F has the same fre- 

 quency as I, and lags in phase behind I by this angle 13°. The total 

 mechanic impedance z' of the diaphragm limits the max. cyclic 

 velocitx' to 



F F 



.}■ = — = rms. kines Z (11) 



z' Zu + z 



F 



or • z' = -r total mechanic absohms Z (12) 



2 Bibliography 9, page 477. 



3 Bibliography 7, 8 and 9. 



