S. Kapadia et Me. Lutman, Nonlinear temporal interactions in click-evoked otoacoustic emissions. II.Experimental data, HEARING RES, 146(1-2), 2000, pp. 101-120
Click-evoked otoacoustic emissions (CEOAEs) are reduced in amplitude by the
presentation of 'suppressor' clicks that either closely lead or follow the
stimulus ('test') clicks. A model described in a companion paper (Kapadia
and Lutman, Hear. Res. 146 (2000) 89-100) shows that such nonlinear tempora
l interactions, as previously reported, may be explained terms of the compr
essive non-linearity of the CEOAE input-output (I-O) function. This paper p
resents the results of a detailed parametric investigation into such nonlin
ear interactions, studied in 12 normal adult ears over a wide range of test
and suppressor click levels and inter-click intervals. The results differ
from those generated by the model in a number of respects. Principally, max
imum suppression is generally obtained for suppressors presented in advance
of test clicks, rather than co-incident with the test clicks. The amount o
f advance depends systematically on the two click levels. The measured supp
ression can also exceed the theoretical maximum allowed by the model. It is
concluded that the nonlinear temporal interactions measured do not simply
reflect CEOAE I-O function non-linearity. They may, instead, arise from dis
turbance of the generator elements from their resting state prior to genera
tion of the CEOAE. These results may also have general implications relatin
g to cochlear responses to transient stimuli and indicate the potential of
CEOAEs in probing aspects of cochlear mechanics. (C) 2000 Elsevier Science
B.V. All rights reserved.