F. Coro et M. Kossl, DISTORTION-PRODUCT OTOACOUSTIC EMISSIONS FROM THE TYMPANIC ORGAN IN 2NOCTUOID MOTHS, Journal of comparative physiology. A, Sensory, neural, and behavioral physiology, 183(4), 1998, pp. 525-531
Distortion-product otoacoustic emissions were measured from the tympan
ic organ of Ascalapha odorata (Noctuidae, Erebinae) and Empyreuma affi
nis (=pugione) (Arctiidae, Ctenuchinae) during stimulation with two pu
re tones of different frequency (f1,f2) within a frequency range betwe
en 5 and 60 kHz. The cubic distortion-product that appears at a freque
ncy of 2f1-f2 showed the largest amplitude and could be used to obtain
''distortion audiograms''. In such audiograms, the maximal distortion
-product otoacoustic emission levels were measured for stimulus freque
ncies that correspond to lowest Al-cell thresholds in each of the two
species. Newly emerged E. affinis showed very low levels of the 2f1-f2
distortion, most of which were within the noise range. In contrast to
vertebrate distortion-product otoacoustic emissions, in neither of th
e species could an optimum f2/f1 ratio be easily defined, and small ra
tios were sufficient to induce the distortions. We conclude that the e
ars of the two moth species exhibit distinctly non-linear mechanical p
roperties. Distortion-product otoacoustic emissions are a good non-inv
asive method for studying the spectral response characteristics of the
mechanics of their auditory organs, despite the fact that their morph
ological characteristics are very different from those in vertebrates.