Timbre and Loudness on the Localisation of Sounds. 279 



Sound 



given. 



Subject's reply. 



Sound 



given. 



Subject's reply. 



Slides A 



135 h. 



G 



45 h. 



Horn B 



o 



90 fa. 







? 90 fa. 



B 



135 h. 



135 h. 



Slides A 



135 h. 



45 h.t 



», B 



45 h. 



45 h. 



B 



90 h. 



90 fa. 



B 



90 h. 



90 fa. 



c 



135 fa. 



135 fa. 



» B 



3 35 h. 



135 fa. 



B 



45 fa. 



45 h. 



„ B 



45 h. 



45 h. 



Horn A 



90 fa. 



90 h. 



c 



45 h. 



135 fa. 



c 



90 fa. 



90 h. 



B 



135 h. 



135 fa. 



„ B 



45 fa. 



45 fa. 



.. B 



90 h. 



? 90 fa. 



Slides A 



45 fa. 



45 h. 



„ B 



135 h. 



135 fa. 



„ B 



45 h. 



45 fa. or 90 h. 



Horn A 



90 h. 



? # . 



Horn A 



90 fa. 



45 h. or 20 fa. 



„ B 



45 h. 



45 fa. 



„ c 



45 fa. 



45 h. 



B 



135 h. 



135 h. 



„ B 



135 fa. 



135 fa. 



'• i, B 



135 fa. 



135 fa. 



Slides A 



90 h. 



45 fa. 



„ B 



90 h. 



90 fa. 



„ B 



90 fa. 



45 fa. or 90 h. 



Slides C 



45 h. 



45 h. 



„ c 



45 fa. • 



45 fa. 



* " It has the quality of 45° fa., but it is not so far back, I think, nor so distant as 90V 

 t " That's tfae 45° h. all right ! " 



That is to say, for 19 estimations in the normal or B position of the 

 horn and slides, only four doubtful or ambiguous answers occurred (11 per 

 cent, of errors), whereas for six estimations in the A or C positions of the 

 horn there were two such answers (17 per cent, of errors), and for seven 

 estimations in the A or C position of the slides there were four wrong 

 answers (57 per cent, of errors). Thus the effect of varying the loudness 

 of the sound was to reduce the certainty of this subject's answers, while the 

 effect of varying the timbre of the sound was to' change the apparent position 

 of the sound. 



It will be noticed that whereas changing the positions of the horn produced 

 greater confusion in the vertical plane, changing the position of the slides 

 produced greater confusion in the horizontal plane. We might be inclined to 

 conclude from this that localisation is based on differences in loudness for 

 sounds in the vertical plane, and on differences in timbre for sounds in the 

 horizontal plane. But we have to remember that 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 that changes in the position of the 

 slides must have affected not only the timbre but also, though much less 

 markedly, the loudness of the sound. 



We have also to bear in mind that in the vertical plane we were 

 dealing with sounds placed at forward (0°), topward (90° v.), and backward 

 (180°) positions, while in the horizontal plane, the sounds were given half- 

 forward (45° h.), to the side (90° h.), and half-backward (135° h.). 



We may, I think, legitimately conclude that for sounds given at 0°, 90° v., 

 and 180°, our localisation is based principally upon differences in loudness, 



