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A Possible Standard of Sound. 



Chas. T. Knipp — University of Illinois. 



( Abstract. ) 



The paper as presented described a source of sound recently brought 

 to the writer's attention, while blowing a mercury vapor trap of pyrex 

 glass, that bids fair to furnish a standard of sound of any desired pitch 

 with no other apparatus than the trap and a bunsen burner. In its sim- 

 plest form the apparatus is an ordinary trap as shown in Fig. 1, having 

 the usual ring seal at M. 



To operate, close A with a sliding piston of cork, let C remain open, 

 and apply a bunsen burner (adjusted to give a fairly hot flame) at B. 

 The tube AB should be held in the flame at an angle so that the central 

 portion M is not unduly heated. When B begins to glow, a pure tone 

 that is readily audible over a large room is emitted at C. The pitch of 

 the sound is dependent upon the length of the vibrating column AB and 

 also upon the length of the side tube MC. Attaching a horn at C 

 intensifies the sound many fold. The only opening is at C, yet a candle 

 placed at this point is instantly blown out. On closer examination it 

 was noticed that a current of air enters the tube C around its edge, 

 and another at the same time escapes from it along its axis. 



There are other conditions that affect the pitch. Those noted thus 

 far are: That heating the region about M destroys the sound; but on 

 the other hand if the flame is removed from B, then C stopped and A 

 opened, the tube will again operate on heating M to redness; that the 

 pitch is raised by the addition of extra side tubes fused to the vibrating 

 column at M, and is instantly lowered when these extra branches are 

 in turn stopped. 



Tubes having different dimensions were constructed. These can 

 be adjusted over wide ranges — each an octave or more — and all give, 

 apparently, clear tones particularly free from overtones. By supplying 

 heat to the end B at a constant rate (as by an electric furnace) the 

 pitch may be kept constant for an indefinite length of time. The ap- 

 paratus should therefore furnish a standard source of sound. 



