388 Prof. S. P. Thompson on Binaural Audition. 



the first, except that it is (so to speak) inverted end for end. 

 The two associated wave-forms might be, for example, the 

 two (A and B) subjoined. The question arises, Can we dis- 



tinguish between the two compound tones corresponding to 

 these forms by leading them separately to the two ears — that 

 is, by listening to them hinaurally ? We have shown that in 

 binaural audition we have a perception of a difference of phase 

 for single tones. Can we go further, and demonstrate the ex- 

 istence of a perception of phase-difference in the components 

 of a compound sound ? 



Helmholtz*, after a very careful consideration of the sub- 

 ject, comes to the conclusion that in ordinary hearing " the 

 quality of the musical portion of a compound tone depends 

 solely on the number and relative strength of its partial simple 

 tones, and in no respect on their difference of phase." Mr. 

 Sedley Taylor f repeats the statement in a more emphatic form: 

 " The ear being deaf to differences of phase in partial-tones, 

 perceives no distinction between such modes of vibration .... 

 but merely resolves them into the same single pair of partial- 

 tones." 



To put the matter to the test of binaural hearing, the follow- 

 ing experiment was arranged : — Two similar glass funnels 

 w r ere attached to equal tubes leading to the two ears: their 

 mouths were placed facing one point, but at right angles to 

 one another. If a vibrating tuning-fork be held at the point 

 toward which the funnels face, it can be so held that the vibra- 

 tions imparted by the two tubes shall be either alike or opposite 

 in phase. For if the ends of the prongs be held towards one 

 funnel so that the axis of the fork coincides with the axis of 



* Sensations of Tone (Ellis's translation), p. 184. 

 t Sound and Music, p. 146. 



