Interferenceallows this defect, at

Interference

allows this defect, at least in principle, to be corrected, for we
can use the principle of Young’s double-slit fringes to achieve a cancellation
of the sound from the left channel that reaches the right ear, and vice versa.
We achieve this, as illustrated in Fig. 8.2, by feeding the left channel to both
loudspeakers – just as in Young’s experiment the same wave arrived at both
slits – but we introduce a phase shift, whose effect is to shift the fringe pattern
to the left or right, so that a node in the interference pattern coincides with
the position of the right ear. The left channel is thus heard only by the left
ear. The converse arrangement similarly limits the right channel to the right
ear.