ACOUSTIC IMPEDANCE. 37 



losses, and if the Wbration amplitude were uniform over the whole 

 diaphragm, would be 789 V 0° acoustic absohms. The mass factor 

 of the diaphragm, as measured electrically, with its usual cover open- 

 ing into the air, was 0.263; so that if this mass factor had been 

 maintained under the geometrical conditions indicated in Figure 3, 

 the acoustic impedance on the outer surface of the diaphragm would 

 be 789 Y 0° X 0.263 = 208 Y 0° mechanic absohms. The actual 

 analj'sis, however, of the results with the tube attached as in Figure 3, 

 made the observed surge impedance on the front surface 187 \ 5?2 

 mechanic absohms. The discrepancy between the computed and 

 observed value of z^ may be attributed to three influences (1) acoustic 

 losses in the tube; (2) the sudden change in tube sectional area from 

 19.3 to 7.55 sq. cm. close to the diaphragm, and (3) a probable change 

 of mass factor ?»/M under the actual conditions of Figure 3. 



