Foley Telephone Mouthpiece 



203 



high sensitivity of the no horn curve at zero distance is undoubtedly 

 due to the fact that the diaphragm of the transmitter was almost ad- 

 jacent to the tube so that the total energy given off at the source was 

 almost all absorbed by the vibrating disc. The rapid falling off of the 

 curves shows vividly how the energy falls off with distance out from the 

 horn. 



The apparatus was also used to make some investigations of the 

 sound pattern about the mouth of the singing tube for which it seemed 



/ A'o horn- 



1. Ordinary flared /lorr?. 



3. Fbraho/ic horn- 



4 Parabolic hotfT rvith disc. 



Fig. 4. 



Distance cf Soarz^/r?^ Tijbe /'ro/n /iorn 

 J.E.BrocA. 

 Graph of curves showing superiority of the parabolic horn. 



to be singularly well adapted. The energy given off by the singing tube 

 seemed to be largely confined to a cone shaped region in front of the 

 tube with the mouth of the tube at the apex. The boundaries of this 

 sound cone seemed to be very sharply defined. It is hoped that in a 

 short time enough data will have been secured so that more definite 

 ideas may be formulated concerning the sound pattern of this cone. 



In concluding I wish to express my thanks to Dr. A. L. Foley, of 

 Indiana University, and Dr. C. T. Knipp, of the University of Illinois, 

 for their kindly interest and many helpful suggestions offered during 

 the progress of the experiments outlined in this research. 



