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Mr. C. S. Myers. The Influence of 



whereas for sounds given at 45°, 90° and 135° in the horizontal plane 

 our localisation is based principally upon differences in timbre ; " principally " 

 because changes in the position of the horn must have affected not only the 

 loudness but also, though much less markedly, the timbre of the sound, and 

 because changes in the positions of the slides must have affected not only the 

 timbre but also, though much less markedly, the loudness of the sound. 



This conclusion is in harmony with other considerations. There are 

 enormous differences between sounds at 0°, 90° v., and 180°, as regards 

 the favourableness of their position for being " caught up " by the pinna. 

 The pinna catches sounds coming from the front better than it catches 

 those coming from the rear ; as is well known, auditory acuity is keener 

 forwards than behind. It is hence not surprising that Ave learn to distinguish 

 fore, aft, and top sounds principally by differences in loudness. On the other 

 hand, sounds given at 45°, 90°, and 135° in the horizontal plane must differ 

 little in loudness ; the difference between the extreme positions, 45° and 135°, 

 is much less than that between positions C and 180° ; 45° and 135° are 

 almost, although not quite, equally favourable positions for the sound to be 

 caught up by the pinna, and indeed 135° is the angle most suitable for the 

 direct entry of the sound into the meatus. 



4. The Role of Tactual Sensibility in Auditory Localisation — 



These experiments appear to prove conclusively not only that variations in 

 timbre and loudness are responsible for our determination of the incidence of 

 sounds but also that cutaneous sensibility can play no part whatever in sound 

 localisation. That cutaneous sensations can play no part so far as concerns 

 laterality is shown by the well-known fact that whereas we are able correctly 

 to localise two simultaneous tones of clearly different pitch, placed one on 

 each side of our head, whatever be their relative loudness, our localisation of 

 two tones thus placed, when they are of identical pitch, depends upon their 

 relative loudness ; if the two tones are equally loud, the sound is localised in 

 the median plane ; as soon as they become of unequal loudness, the sound is 

 immediately localised in that ear which receives the stronger stimulus.* 



Now, if the sounds falling on each ear gave rise to tactual sensations, there 

 can be no reason why, whatever their pitch and relative loudness, two such 

 tones should not be correctly localised, one on one side of the head, the other 

 on the other. On the other hand, it is quite clear that sound localisation 

 rests on an auditory not on a tactual, sensory basis, since when the tones 

 are of identical pitch only a single sound is heard and its localisation is 



* I omit for simplicity's sake the consideration of phase difference here (see, however, 

 footnote to p. 267). 



