Distortion product otoacoustic emission fine structure analysis of 50 normal-hearing humans

In humans, when the medial olivocochlear ͑MOC͒ pathway is activated by noise in the opposite ear, changes in distortion product otoacoustic emission ͑DPOAE͒ level, i.e., the MOC reflex, can be recorded in the test ear. Recent evidence suggests that DPOAE frequency influences the direction ͑suppression/enhancement͒ of the reflex. In this study, DPOAEs were recorded at fine frequency intervals from 500 to 2500 Hz, with and without contralateral acoustic stimulation ͑CAS͒ in a group of 15 adults. The MOC reflex was calculated only at DPOAE frequencies corresponding to peaks in the fine structure. Additionally, inverse fast-Fourier transform was conducted to evaluate MOC effects on individual DPOAE components. Results show the following: ͑1͒ When considering peaks only, the mean MOC reflex was −2.05 dB and 97% of observations reflected suppression, ͑2͒ CAS reduced distortion characteristic frequency component levels more than overlap component levels, and ͑3͒ CAS produced an upward shift in fine structure peak frequency. Results indicate that when the MOC reflex is recorded at DPOAE frequencies corresponding to fine structure maxima ͑i.e., when DPOAE components are constructive and in phase͒, suppression is reliably observed and level enhancement, which probably reflects component mixing in the ear canal rather than strength of the MOC reflex, is eliminated.

Section: A Normative Fine Structuresupporting

confidence: 82%

Considering distortion product otoacoustic emission fine structure in measurements of the medial olivocochlear reflex

Abdala

Mishra

Williams

2009

“…Although some ears with hearing loss may produce DPOAE fine structure, previous reports indicate that it is only observed when auditory function at the cochlear location from which the reflection source arises is normal or nearly normal (Mauermann et al, 1999a,Stover et al, 1999Konrad-Martin et al, 2002). Additionally, as observed in the present study, and in previously reported data (e.g., Dhar and Shaffer, 2004;Johnson et al, 2006b;Reuter and Hammershoi, 2006), fine structure is less prevalent in ears with normal hearing for frequencies surrounding 4 kHz. Given these observations, it was unlikely that we would see an effect of suppression in the ears with hearing loss or in ears with normal hearing at 4 kHz.…”

Section: A Dichotomous Decisionsupporting

confidence: 75%

Distortion product otoacoustic emissions: Cochlear-source contributions and clinical test performance

Johnson

Neely

Kopun

et al. 2007

It has been proposed that the clinical accuracy of distortion product otoacoustic emissions (DPOAEs) is affected by the interaction of distortion and reflection sources contributing to the response. This study evaluated changes in dichotomous-decision test performance and threshold-prediction accuracy when DPOAE source contribution was controlled. Data were obtained from 205 normal and impaired ears with L 2 ranging from 0 to 80 dB SPL and f 2 = 2 and 4 kHz. Data were collected for control conditions (no suppressor, f 3 ) and with f 3 presented at 3 levels that previously had been shown to reduce the reflection-source contribution. The results indicated that controlling source contribution with a suppressor did not improve diagnostic accuracy (as reflected by ROC curve area) and frequently resulted in poorer test performance compared to control conditions. Likewise, correlations between DPOAE and behavioral thresholds were not strengthened when using the suppressors to control source contribution. While improvements in test accuracy were observed for a subset of subjects (normal ears with the smallest DPOAEs and impaired ears with the largest DPOAEs), the lack of improvement for the larger, unselected subject group suggests that DPOAEs should be recorded in the clinic without attempting to control the source contribution with a suppressor.

“…Spontaneous, transient evoked, and stimulus frequency OAEs show a consistent spacing pattern that can be characterized to the value f / ⌬f = 16, where f is the center frequency and ⌬f is the frequency distance between adjacent SOAEs or maxima/minima of transient or stimulus frequency OAEs ͑e.g., Zwicker, 1990;Shera, 2003͒. Although shown not to coincide exactly with other types of OAEs ͑Lutman and Deeks, 1999͒, approximate correspondence of DPOAE fine structure spacing to these other measures has been demonstrated ͑Reuter and Hammershoi, 2006;Dhar and Abdala, 2007͒. Based on this estimate of fine structure spacing, measurements made at f, f Ϯ ͑f / 4͒, and f Ϯ ͑f / 8͒, where f is the frequency of interest, should allow the sampling of a data point at or near the maximum of that particular fine structure period.…”

Section: A Reduction and Enhancement Of Dpoae Levelmentioning

confidence: 99%

Contralateral acoustic stimulation alters the magnitude and phase of distortion product otoacoustic emissions

Deeter

Abel

Calandruccio

et al. 2009

Activation of medial olivocochlear efferents through contralateral acoustic stimulation ͑CAS͒ has been shown to modulate distortion product otoacoustic emission ͑DPOAE͒ level in various ways ͑enhancement, reduction, or no change͒. The goal of this study was to investigate the effect of a range of CAS levels on DPOAE fine structure. The 2f 1 -f 2 DPOAE was recorded ͑f 2 / f 1 = 1.22, L 1 = 55 dB, and L 2 =40 dB͒ from eight normal-hearing subjects, using both a frequency-sweep paradigm and a fixed frequency paradigm. Contamination due to the middle ear muscle reflex was avoided by monitoring the magnitude and phase of a probe in the test ear and by monitoring DPOAE stimulus levels throughout testing. Results show modulations in both level and frequency of DPOAE fine structure patterns. Frequency shifts observed at DPOAE level minima could explain reports of enhancement in DPOAE level due to efferent activation. CAS affected the magnitude and phase of the DPOAE component from the characteristic frequency region to a greater extent than the component from the overlap region between the stimulus tones. This differential effect explains the occasional enhancement observed in DPOAE level as well as the frequency shift in fine structure patterns.