reverse correlation method (Fay, 1997; Fay and Edds-
Walton, 1997b). These show that each species has essentially
two di¡erently tuned peripheral channels and
that one of them can be transformed into the other by a
very simple ¢lter, equivalent to a spectral tilt. This tilt
could arise from micromechanical processes within the
saccule.