PAPERS PRESENTED AT GENERAL SESSIONS 23 



constant. The best means of supplying heat is by elec- 

 tric current. 



13. The dimensions of the various diameters of the 

 tube are critical; however, as stated above, the various 

 lengths are not. 



14. The open end of the tube forms practically a point 

 source of sound, — little or no sound coming from the 

 other portions of the tube. 



15. The tube when the open end is sealed is, on heat- 

 ing, set in violent vibration, yet it emits no sound. This 

 vibration may be converted into sound by placing closed 

 end on a proper resonating body. 



16. The temperature difference between the cold por- 

 tion and hot tip when the tune is sounding is about 400° C 

 or YoO^F. 



17. The tube may be made to sing by cooling the body 

 of tube to the temperature of liquid air, i. e. to — 180° C or 

 about — 300 °F, and leaving the tip (that is ordinarily 

 heated) at room temperatures. 



18. The temperature difference necessary when liquid 

 air is used is about 200° C. 



19. By extrapolation this means a temperature differ- 

 ence of only 80° C when the body of the tube is cooled to 

 absolute zero. 



20. Recent experiments show that the energy neces- 

 sary to maintain the sound is from 2 to 3% of that sup- 

 plied to the tube. 



Experiments illustrating most of the above items were 

 performed. 



The following physical explanation of the action of 

 the new singing tube is offered :* 



In the organ pipe, energy is supplied by a stream of air 

 which encourages the vibrations in a one-sided way, so 

 that the vibrating column receives an impulse each time 

 when the air moves upward towards the node in the 

 middle of the pipe. Fig. 1, and receives no impulse in the 

 opposite motion. It looks as if a pendulum were kept 

 in oscillation by receiving at one end of its path an im- 

 pulse always in the same direction. If we would apply 



• In collaboration with Dr. Jakob Kunz, University of Illinois. 



