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The Effect of Age and Stimulus Parameters on the Optimum f2/f1 Ratio for DPOAEs

Canadian Acoustical Association / Association canadienne d'acoustique
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  • Musicology
  • Physics


THE EFFECT OF AGE AND STIMULUS PARAMETERS ON THE OPTIMUM f 2/ f i RATIO FOR DPOAEs. David K. Brown, Jos J. Eggermont & Barry P. Kimberley The University of Calgary, Calgary, Alberta, Canada Distortion Product O toacoustic Emissions (DPOAE) are com m only used to study the pre-neural activity o f the cochlea in adults and infants. T he param eters used to generate the optimum D PO A E have been studied in adults (see P robst et al., 1991 for rev iew ). O ne o f these parameters is the optimum f2 /f i ratio, this ratio between the primary tones can influence the m axim um amplitude o f the DPOAE. An early report indicated that the optimum f2 / f i ratio was 1.25 (Kemp & Brow n, 1983). There has been agreement across studies that in adults the optimum f2 /f i ratio is approximately 1.2. Harris et al. (1989) found the optimum ratio to be 1.22, but they also described an inverse relationship between optimum f2 /fi ratio and the frequency of the D PO A E with larger ratios required at 1 kHz than at 4 kHz. In addition, they reported that the optimal ratio changed as a function o f the intensity o f the prim aries in such as way as the intensity o f the primaries increased, the ratio used to elicit a maximal D P E amplitude also increased. Although this ratio w as from studies in the adult, it was used as the f2 /f i ratio when testing infants. Brown et al. (1994) investigated the optim um f2 /f i ratio at 2 and 4 kHz in term-born infants and found the ratio to be 1.2 which was in agreement with the optimum ratio for adults. This study measured D PO A Es in 3 infant groups (30-33 wks.; 34-37 wks.; 38-42 wks.) and an adult group. Each group had 40 subjects with the exception of the youngest preterm group which only had 25 infants. DPOA Es were measured from one ear o f each of the 145 subjects tested. Each subject was tested at six f2 frequencies from 10 to 1.7 kHz in half octave steps. The f2 tone is fixed at a given frequency and the f l tone is swept

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