The level of cubic distortion measured in the human ear canal reaches
a peak when the distortion frequency falls approximately half-an-octav
e below that of the higher of two stimulus tones. The peak is thought
to be indicative of a bandpass filter in the cochlea. The properties o
f the distortion peak have been measured during the administration of
aspirin (3.84 g/day for 2 days) in eight human volunteers. In three of
the subjects, there was a downward shift of the center frequency of t
he distortion peak by as much as 200 Hz during aspirin consumption, bu
t no significant change in Q3 dB of the peak. In two of these subjects
, the shift in distortion peak was not associated with a change in psy
chophysical threshold. The mean group delay of the emitted distortion
was reduced by approximately 0.5 ms in four of the eight subjects. The
measurement of stimulus frequency emission (SFE) did not reveal any d
ownward shift of features in the spectrum corresponding to those seen
for the distortion peak. It is concluded (1) that aspirin affects the
resonance frequency of the bandpass filter revealed by distortion meas
urement, but not its tuning; and (2) that the bandpass filter is disso
ciated from the mechanism responsible for the ''fine structure'' in th
e SFE spectrum.