Volume 111, Issue 4, April 2002
Index of content:
- PHYSIOLOGICAL ACOUSTICS 
Sources of DPOAEs revealed by suppression experiments, inverse fast Fourier transforms, and SFOAEs in impaired ears111(2002); http://dx.doi.org/10.1121/1.1455024View Description Hide Description
DPOAE sources are modeled by intermodulation distortion generated near the place and a reflection of this distortion near the DP place. In a previous paper, inverse fast Fourier transforms (IFFTs) of DPOAE filter functions in normal ears were consistent with this model [Konrad-Martin et al., J. Acoust. Soc. Am. 109, 2862–2879 (2001)]. In the present article, similar measurements were made in ears with specific hearing-loss configurations. It was hypothesized that hearing loss at or DP frequencies would influence the relative contributions to the DPOAE from the corresponding basilar membrane places, and would affect the relative magnitudes of SFOAEs at frequencies equal to and DPOAEs were measured with varied, and a suppressor near was 25–55 dB SPL SFOAEs were measured at and at 2.7 kHz (the average produced by the sweep) for stimulus levels of 20–60 dB SPL. SFOAE results supported predictions of the pattern of amplitude differences between SFOAEs at 4 and 2.7 kHz for sloping losses, but did not support predictions for the rising- and flat-loss categories. Unsuppressed IFFTs for rising losses typically had one peak. IFFTs for flat or sloping losses typically have two or more peaks; later peaks were more prominent in ears with sloping losses compared to normal ears. Specific predictions were unambiguously supported by the results for only four of ten cases, and were generally supported in two additional cases. Therefore, the relative contributions of the two DPOAE sources often were abnormal in impaired ears, but not always in the predicted manner.
Pure-tone threshold estimation from extrapolated distortion product otoacoustic emission I/O-functions in normal and cochlear hearing loss ears111(2002); http://dx.doi.org/10.1121/1.1460923View Description Hide Description
A new method for direct pure-tone threshold estimation from input/output functions of distortion product otoacoustic emissions (DPOAEs) in humans is presented. Previous methods use statistical models relating DPOAE level to hearing threshold including additional parameters e.g., age or slope of DPOAE I/O-function. Here we derive a DPOAE threshold from extrapolated DPOAE I/O-functions directly. Cubic distortion products and pure-tone threshold at were measured at 51 frequencies between and 8 kHz at up to ten primary tone levels between and 20 dB SPL in 30 normally hearing and 119 sensorineural hearing lossears. Using an optimized primary tone level setting that accounts for the nonlinear interaction of the two primaries at the DPOAE generation site at the pressure of the distortion product is a linear function of the primary tone level Linear regression yields correlation coefficients higher than 0.8 in the majority of the DPOAE I/O-functions. The linear behavior is sufficiently fulfilled for all frequencies in normal and impaired hearing. This suggests that the observed linear functional dependency is quite general. Extrapolating towards yields the DPOAE threshold for There is a significant correlation between DPOAE threshold and pure-tone threshold Thus, the DPOAEs that reflect the functioning of an essential element of peripheral sound processing enable a reliable estimation of cochlear hearing threshold up to hearing losses of 50 dBHL without any statistical data.