Influence of in situ , sound-level calibration on distortion-product otoacoustic emission variability

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Distortion-product otoacoustic emissions (DPOAEs) were used to describe suppression growth in normal-hearing humans. Data were collected at eight f 2 frequencies ranging from 0.5 to 8 kHz for L 2 levels ranging from 10 to 60 dB sensation level. For each f 2 and L 2 combination, suppression was measured for nine or eleven suppressor frequencies (f 3 ) whose levels varied from À20 to 85 dB sound pressure level (SPL). Suppression grew nearly linearly when f 3 % f 2 , grew more rapidly for f 3 < f 2 , and grew more slowly for f 3 > f 2 . These results are consistent with physiological and mechanical data from lower animals, as well as previous DPOAE data from humans, although no previous DPOAE study has described suppression growth for as wide a range of frequencies and levels. These trends were evident for all f 2 and L 2 combinations; however, some exceptions were noted. Specifically, suppression growth rate was less steep as a function of f 3 for f 2 frequencies 1 kHz. Thus, despite the qualitative similarities across frequency, there were quantitative differences related to f 2 , suggesting that there may be subtle differences in suppression for frequencies above 1 kHz compared to frequencies below 1 kHz.

Section: Methodsmentioning

confidence: 94%

Growth of suppression in humans based on distortion-product otoacoustic emission measurements

Gorga

Neely

Kopun

et al. 2011

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“…The source calibration used in the present study and the earlier study by Scheperle et al ͑2008͒ can be expected to accurately decompose incident and reflected pressure waves in the ear canal. FPL and IPL are derived sound-level measures resulting from the source calibration and, more specifically, the Thevenin-equivalent source characteristics ͑imped-ance and pressure͒.…”

Section: Discussionmentioning

confidence: 99%

Comparison of in-situ calibration methods for quantifying input to the middle ear

Lewis

McCreery

Neely

et al. 2009

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Sound pressure level in-situ measurements are sensitive to standing-wave pressure minima and have the potential to result in over-amplification with risk to residual hearing in hearing-aid fittings. Forward pressure level ͑FPL͒ quantifies the pressure traveling toward the tympanic membrane and may be a potential solution as it is insensitive to ear-canal pressure minima. Derivation of FPL is dependent on a Thevenin-equivalent source calibration technique yielding source pressure and impedance. This technique is found to accurately decompose cavity pressure into incident and reflected components in both a hard-walled test cavity and in the human ear canal through the derivation of a second sound-level measure termed integrated pressure level ͑IPL͒. IPL is quantified by the sum of incident and reflected pressure amplitudes. FPL and IPL were both investigated as measures of sound-level entering the middle ear. FPL may be a better measure of middle-ear input because IPL is more dependent on middle-ear reflectance and ear-canal conductance. The use of FPL in hearing-aid applications is expected to provide an accurate means of quantifying high-frequency amplification.

“…Neely and Gorga (1998) compared behavioral threshold measurements between 0.5 and 8 kHz based on pressure and acoustic intensity calibration and concluded that intensity calibration in the ear was preferable above 2 kHz. Scheperle et al (2008) reported that an in-theear stimulus calibration based on forward pressure level or intensity level provided more consistent DPOAE measurements between 2 and 8 kHz compared to a calibration based on total pressure. Based on analyses of measurements between 0.25 and 6 kHz, Withnell et al (2009) proposed that either forward pressure or the fraction of total pressure at the tympanic membrane that is not reflected at the tympanic membrane be used to specify behavioral hearing threshold rather than total pressure.…”

Section: Constant Stimulus-level Proceduresmentioning

confidence: 99%

Specification of absorbed-sound power in the ear canal: Application to suppression of stimulus frequency otoacoustic emissions

Keefe¹,

Schairer²

2011

An insert ear-canal probe including sound source and microphone can deliver a calibrated sound power level to the ear. The aural power absorbed is proportional to the product of mean-squared forward pressure, ear-canal area, and absorbance, in which the sound field is represented using forward (reverse) waves traveling toward (away from) the eardrum. Forward pressure is composed of incident pressure and its multiple internal reflections between eardrum and probe. Based on a database of measurements in normal-hearing adults from 0.22 to 8 kHz, the transfer-function level of forward relative to incident pressure is boosted below 0.7 kHz and within 4 dB above. The level of forward relative to total pressure is maximal close to 4 kHz with wide variability across ears. A spectrally flat incident-pressure level across frequency produces a nearly flat absorbed power level, in contrast to 19 dB changes in pressure level. Calibrating an ear-canal sound source based on absorbed power may be useful in audiological and research applications. Specifying the tip-to-tail level difference of the suppression tuning curve of stimulus frequency otoacoustic emissions in terms of absorbed power reveals increased cochlear gain at 8 kHz relative to the level difference measured using total pressure.