On the relationships between the fixed-f(1), fixed-f(2), and fixed-ratio phase derivatives of the 2f(1)-f(2) distortion product otoacoustic emission

For primary frequency ratios, f(2)/f(1), in the range 1.1-1.3, the fixed-f( 1) ("f(2)-sweep") phase derivative of the 2f(1)-f(2) distortion product oto acoustic emission (DPOAE) is larger than the fixed-f(2) ("f(1)-sweep") one. It has been proposed by some researchers that part or;all of the differenc e between these delays may be attributed to the so-called cochlear filter ' 'build-up'' or response time in the DPOAE generation region around the f(2) tonotopic site. The analysis of an approximate theoretical expression for the DPOAE signal [Talmadge et al., J. Acoust. Soc. Am. 104, 1517-1543 (1998 )] shows that the contributions to the phase derivatives associated with th e cochlear filter response is small. It is also shown that the difference b etween the phase derivatives can be qualitatively accounted for by assuming the approximate scale invariance of cochlear mechanics. The effects of DPO AE fine structure on the phase derivative are also explored, and it is foun d that the interpretation of the phase derivative in terms of the phase var iation of a single DPOAE component can be quite problematic. (C) 2000 Acous tical Society of America. [S0001-4966(00)05710-6].