ON HEARING WITH TWO EARS. 
93 
5. — This localisation of the subjective acoustic image’' is 
independent of the pitch of the sound. This is proved for sounds 
of all degrees of pitch and of every possible complexity of 
timbre ” by the employment of telephones. If the sounds are 
transmitted by tubes of india-rubber the localisation is manifested 
only for simple sounds : for complex sounds the difference of length 
which produces complete, opposition of phase for the fundamental 
sound does not give the same effect for all the upper partial tones. 
6. — This last observation suggests a method for analysing 
complex sounds ivithout the employment of Mesonators. In fact, 
by binaural audition, it is possible to recognise a difference 
between two complex sounds, the separate partial tones of which 
are present in equal numbers, and of the same pitch and 
intensity, and which present only differences of phase. This 
proposition, it will be remarked, contradicts the assertion of 
Helmholtz that the ear cannot distinguish differences of phase. 
This conclusion, which was drawn from the joint sensations of the 
ears, is negatived by the phenomena which are observed when the 
sounds that differ in phase only are led separately to the two ears. 
7. — When the difference of phase of the tivo tones thus led to 
the ears is less than half an undulation, the sensation is only 
partially localised in the bach of the head, and partly in the ears. 
The sensation is not simple nor capable of exact description. 
8. — If the difference of phase is com]}lete, but the two sounds of 
unequal intensity, the “ acoustic image,” instead of being at the 
middle of the bach of the shull, is nearer to the side of that ear 
ivhich is receiving the louder sound. This can be shown by 
taking tubes of unequal diameters, or with two telephones in 
which the magnets are not equally strong. 
9. — To binaural audition the consonant intervals appear 
rough, and the dissonant intervals extremely harsh. If different 
simple tones are led to the ear, as c’ and e' , or c’ and ff, the effect 
is disagreeable. The seventh c' V unendurably grating. 
