of Binaural Audition. 353 



a new instrument — the wave-siren* . In this instrument disks, 

 upon whose edges have been cut the wave-forms of mistuned 

 consonances, are rotated in front of a nozzle through which air 

 is blown, and yield, when rotated slowly, beats 9 but when 

 rotated rapidly, beat-tones. 



3. The author has recently submitted to examination by 

 binaural hearing the case of mistuned consonances of the form 

 nil, with the following results. 



(a) Mistuned Unison. — Two stopped organ-pipes (C of 4-foot 

 octave), sometimes blown from one source, sometimes from 

 two, were used, one being kept to exact tuning, the other 

 raised and lowered in pitch by altering position of stopper or 

 by holding an obstacle to the lip of the pipe. A glass funnel 

 was placed in front of each pipe ; and two indiarubber tubes 

 led the sounds to the ears independently. Beats were heard, 

 which ceased if either pipe was nipped. The rise and fall of 

 the individual tone of the one pipe could also be distinguished. 

 The beats appeared to wander from ear to ear. 



(b) Mistuned Octave. — A similar arrangement applied to 

 the mistuned octave entirely confirmed the second point of 

 Mr. Bosanquet's research. Whether the upper or the lower note 

 of the octave interval was tampered with, and whether raised 

 or lowered, beats were heard, and those beats consisted exclu- 

 sively of variations in loudness of the lower note. That ear 

 which received the higher note heard merely variations in 

 pitch when that note was tampered with, heard no variations 

 either of pitch or of intensity when the lower note was tam- 

 pered with. The ear which received the lower note heard 

 merely variations of intensity (beats) when the upper note 

 was tampered with, but heard variations both of intensity and 

 pitch when the lower note was tampered with. 



Two forks giving C and C" (mistuned) were next tried 

 side by side in a room, funnels placed opposite them being 

 connected to separate ears. Here the sounds mingled to some 

 extent before reaching the ears, and beats were heard by both 

 ears ; but very careful listening showed that, as before, the 

 beats were variatious of loudness of the lower tone. When 

 this was relatively much the louder of the two, the beats were 

 best heard in the ear listenino; to the higher fork. When the 

 higher fork was the louder of the two, the beats were much 

 more distinct to the ear listening to the lower. 



The experiment was then repeated, but with the essential 



difference that the forks were sounded in different rooms, and 



their sounds conveyed to the observer by indiarubber tubes 



through the key-holes of the doors. No sound was audible 



* Wied. Ann. March 1881, Bd. xii. Heft 3, p. 335. 



