314 ILLINOIS STATE ACADEMY OF SCIENCE 



on either tube. This wave demonstrates the ease with 

 which the dermatj^pe diaphragm followed a complex 

 wave form. At least six wave forms can be traced in this 

 curve. 



Waves C, D, and E were taken by C. T. Knipp during 

 the author's absence. In C, the two L-form tubes used 

 were adjusted to each, giving its maximum tone with a 

 resonator attached. A slight adjustment of either gave 

 any desired beat frequency. This curve is exceedingly 

 clear cut and bears a critical study under a glass. For 

 each tube the energy was being supplied by one burner ; 

 hence the components of the wave should be nearly pure 

 sine waves. Ununiform motion of the film makes the 

 beats appear to be of diiferent sizes. In D the same two 

 tubes were adjusted to nearly unison, giving six or seven 

 beats per second. The other conditions were the same 

 as in C. In E there was superimposed upon D the tone 

 emitted by a high pitch organ pipe blown to sound its 

 fundamental. The film was moving some faster, other- 

 wise the conditions were the same. Wave F was taken 

 from three open organ pipes sounding together. The 

 pipes ranged from a very low to a very high pitch, and 

 were being blown with considerable jDressure so as to 

 produce overtones in each one. This is not a hap-hazard 

 curve as it appears at first sight, but rather an ordered 

 succession of a single configuration, three of which ap- 

 pear on the photograph. Wave G represents a note from 

 a French horn. The wave forms represented in B, E, F 

 and G should remove from the minds of even the most 

 skeptical any doubt as to the sensitivity of the dia- 

 phragm. 



The author wishes to express his thanks to Professor 

 C. T. Knipp for his encouragement and assistance in this 

 work, and to Professor A. P. Carman for the facilities 

 of the department. 

 Laboratory of Physics 



University of Illinois 

 January, 1922 



