An <i>in situ</i> calibration for hearing thresholds

Withnell, Robert H.; Jeng, Patricia S.; Waldvogel, Kelly; Morgenstein, Kari; Allen, Jont B.

doi:10.1121/1.3075551

Cited by 43 publications

(47 citation statements)

References 22 publications

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“…2, for which the maximum L FE was 6 dB at the 75th percentile. Experimental results from Withnell et al (2009) are also generally consistent with Keefe and Abdala (2007) and the present results. Differences between studies emphasize the importance of individual variability in ear-canal acoustics, including variability in the depth of insertion of the probe.…”

Section: B Acoustic Transfer-function Measurementssupporting

confidence: 81%

“…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. Calibrating the ear-canal stimulus according to forward pressure level has also been suggested for hearing-aid applications using probe-microphone measurements in the ear canal Lewis et al, 2009) and compared with calibrations using total pressure level in DPOAE measurements (Burke et al, 2010).…”

Section: Constant Stimulus-level Proceduresmentioning

confidence: 99%

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

Keefe¹,

Schairer²

2011

The Journal of the Acoustical Society of America

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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.

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Section: B Acoustic Transfer-function Measurementssupporting

confidence: 81%

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

The Journal of the Acoustical Society of America

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“…Data is presented from six subjects, four female and two male. The method for data collection has been described previously (see Withnell et al 2009). Briefly, signal generation and data acquisition was computer-controlled using the Mimosa HearID system with version R4 software module (www.mimosaacoustics.com).…”

Section: Subjects and Data Collectionmentioning

confidence: 99%

An Analysis of the Acoustic Input Impedance of the Ear

Withnell

Gowdy

2013

JARO

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Ear canal acoustics was examined using a onedimensional lossy transmission line with a distributed load impedance to model the ear. The acoustic input impedance of the ear was derived from sound pressure measurements in the ear canal of healthy human ears. A nonlinear least squares fit of the model to data generated estimates for ear canal radius, ear canal length, and quantified the resistance that would produce transmission losses. Derivation of ear canal radius has application to quantifying the impedance mismatch at the eardrum between the ear canal and the middle ear. The length of the ear canal was found, in general, to be longer than the length derived from the one-quarter wavelength standing wave frequency, consistent with the middle ear being mass-controlled at the standing wave frequency. Viscothermal losses in the ear canal, in some cases, may exceed that attributable to a smooth rigid wall. Resistance in the middle ear was found to contribute significantly to the total resistance. In effect, this analysis "reverse engineers" physical parameters of the ear from sound pressure measurements in the ear canal.

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“…Data for this study was drawn from a larger data set obtained as part of an NIH-funded Small Business Innovation Research grant. The method for data collection has been described previously, see Withnell et al [11]. This study was completed with the approval of the Indiana University Institutional Review Board.…”

Section: Methodsmentioning

confidence: 99%

Modeling Ear-Canal Acoustics, Incorporating Visco-Thermal Effects and the Influence of the Middle Ear

Gowdy¹,

Withnell²,

Shera³

et al. 2011

AIP Conference Proceedings

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Abstract. The ear canal, below about 6 kHz, is well described by a uniform cylinder (sound propagates predominantly as plane waves) with the middle ear being a non-rigid termination. A nonrigid termination can be viewed as altering, as a function of frequency, the acoustic length and radius of the cylinder. It is generally assumed that sound transmission in the ear canal over this frequency range is lossless. This paper presents a method for calculating the influence of visco-thermal losses and the middle ear on ear canal acoustics. The acoustic input impedance was derived from sound pressure measurements in the ear canal and then a nonlinear least-square-fit to the data with a one-dimensional model incorporating visco-thermal losses generated length, radius, and middle ear impedance parameters. It was found that a rigid wall assumption for visco-thermal calculations was insufficient to account for damping in the ear canal. The properties of the ear canal wall (not being a rigid, low-friction surface), incorporated into visco-thermal losses as a scaling factor, provided a better fit to the data. Viscous and thermal losses were both found to affect sound propagation in the ear canal, viscous losses being more significant, altering the acoustic input impedance of the ear primarily in the region of the standing wave frequency. The model data suggests that the middle ear influences ear canal acoustics up to about 3 kHz.

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An in situ calibration for hearing thresholds

Cited by 43 publications

References 22 publications

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

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

An Analysis of the Acoustic Input Impedance of the Ear

Modeling Ear-Canal Acoustics, Incorporating Visco-Thermal Effects and the Influence of the Middle Ear

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