title: Clinical significance of relative probe-tone levels on distortion product otoacoustic emissions.
abstract: The effect of systematic variations in the relative levels (L1, L2) of two primary tones (f1, f2) on the amplitude of the distortion product otoacoustic emission (DPOAE) at 2f1-f2 and f1 < f2 was investigated in 14 ears from 7 normally hearing human subjects. The primary tones (f2:f1 = 1.23) were geometrically centred at the standard clinical frequencies of 0.5, 1, 1.5, 2, 3, 4, 6 and 8 kHz. The quantity L1-L2 was varied systematically from -10 dB through + 10 dB with L2 held constant at 75 dB SPL for negative values, L1 held constant at 75 dB SPL for positive values, and L1 = L2 = 75 dB SPL at 0 dB relative difference. The maximum amplitudes of the distortion products were generated when L1 = L2 at all geometric centre frequencies except 8 kHz. The reduction of the DPOAE with reduction of L1 was linear at a rate that gradually increased as a function of geometric mean frequency. To a lesser extent, the reduction of the DPOAE with reduction of L2 also was linear but at a rate that systematically decreased as a function of geometric mean frequency. The results suggest, that to maximize the level of the distortion product for clinical purposes, the relative levels of the primary tones should be equal to each other, at least when overall stimulus levels are around 75 dB SPL and f2:f1 = 1.23.
authors.affiliation: Department of Otolaryngology, Head & Neck Surgery, University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: A N
authors.initials: AN
authors.lastname: Rasmussen
authors.forename: G R
authors.initials: GR
authors.lastname: Popelka
authors.forename: P A
authors.initials: PA
authors.lastname: Osterhammel
authors.forename: L H
authors.initials: LH
authors.lastname: Nielsen
mesh_terms: D000158:Acoustic Impedance Tests; D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D003051:Cochlea / Q000502:physiology*; D007758:Ear, Inner / Q000502:physiology*; D004432:Ear, Middle / Q000502:physiology; D005260:Female; D006198:Hair Cells, Auditory / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged