( 423 ) 



in the sound free cabinet, which has been internally covered with 

 trichopiese, the greatest distance at which sound is still perceptible is 

 determined for the intensity of sound in the maximumplane and for 

 that in the discovered "Unterschiedsschwelle" plane. If we accept that 

 in case of absence of reverberations, as we may suppose here, the 

 sound intensities decrease proportionate to the quadrates of the dis- 

 tances, the sound intensities stand mutually in the same proportion as 

 the quadrates of those distances. If we call the distance at which 

 the tone sound is perceptible in the plane of maximum sound r and 



7* 7* 



that for the somewhat weaker sound r„, then the quotient — ■:i — ■ 



represents evidently the "Unterschiedsschwelle", which in this case 

 may be indicated as "untere Unterschiedsschwelle" because the stimula- 

 tion distinguished from the chief is taken weaker than the chief 

 stimulation. 



TABLE I. Experiments with the tuning-fork. 



Experiments with organ-pipes. 



An accurately tuned, wide, covered, wooden organ-pipe is placed 

 in a felt tent in a room at the side of the soundfree cabinet in such 



