Components of the 2f(1)-f(2) distortion-product otoacoustic emission in a moth

The noctuoid moth Empyreuma affinis has a simple tympanal organ with only t wo receptor cells attached to the eardrum. As in vertebrates, the growth of distortion-pro duct otoacoustic emissions (DPOAE) with increasing stimulus level is characterized by two distinct components. An initial increase of DPOAE level for f(2) levels in the range of 30-65 dB SPL is followed by a s econd steep growth of the DPOAE at f(2) levels above 65 dB SPL. Both compon ents increase at a slope of about 2 dB/dB and the difference between both c omponents was used to assess a mechanical gain of the tympanal organ of 17 dB (n = 23), At around 65 dB SPL, a notch in the level function coincides w ith an abrupt phase change of up to 180 degrees. The sensitive component in duced by f(2) levels below 65 dB SPL is selectively affected by application of ethyl ether and disappears more quickly than the high-level component d uring ongoing deterioration of the moth preparation. (C) 2001 Elsevier Scie nce B.V. All rights reserved.