Sound Condensers 



191 



IMPROVED DESIGNS OF SOUND CONDENSERS. 



Arthur L. Foley, Indiana University. 



The writer has shown in former papers that a number of the gen- 

 erally accepted theories in regard to the passage of sound through 

 tubes^ and the action of horns" are not tenable. The theory that when 

 a horn is used as a sound "condenser" all or even the greater part of 

 the energy entering the large end is condensed at the small end is far 

 from the truth. Sound waves do not pass through a horn, like shot or 

 water poured into a funnel. The energy condensed at the small end of 

 a conical oi- flared horn is not even approxunately equal to that enter- 



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Fig. 1. Cress section of flared horn, showing how wave energy is reflected bacl\- 

 ward and out of the large end. 



ing the large end. If the horn is one of large angle, the condensed 

 energy is usually but a small fraction of the entering energy. The 

 major part of the entering energy is lost by reflection; it backs out of 

 the horn at the end it entered. 



Owing to the fact that sound waves are long, compared to light 

 waves, one can not — using sound reflecting surfaces of usual size, expect 

 close agreement between optical and acoustical phenomena. Sound 

 diffraction is a most disturbing factor. However, there is no reason 

 why Huygen's theory should not be applied to determine the direction 



1 The Speed of Sound Pulses in Pi|)es. Phys. Rev.. N.S.. Vol. XIV., No. 



Aug. 



1919. 



The Velocity of Sound Waves in Tubes. Proc. Ind. Acad. Sci., i;ili). 

 - A Photof>raphic Study of Sound Pulses Between Curved Walls and Sound Amplifica- 

 tion by Horns. Phys. Rev., S.S.. Vol. XX, No. fi, Dec, 1922. 



"Proc. 38th Meeting. 1922 (192:j)." 



