Non-invasive estimation of middle-ear input impedance and efficiency

Lewis, James D.; Neely, Stephen T.

doi:10.1121/1.4927408

Cited by 20 publications

(5 citation statements)

References 47 publications

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“…The model ear-canal input impedance falseZec is related to its middle-ear impedance falseZme by elements of the ear-canal transmission matrix (see Lewis & Neely 2015):…”

Section: Methodsmentioning

confidence: 99%

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Conductive Hearing Loss Estimated From Wideband Acoustic Immittance Measurements in Ears With Otitis Media With Effusion

Merchant

Neely

2022

Ear &Amp; Hearing

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Objectives: Previous work has shown that wideband acoustic immittance (WAI) is sensitive to the volume of effusion present in ears with otitis media with effusion (OME). Prior work also demonstrates that the volume of the effusion appears to drive, or at least play a significant role in, how much conductive hearing loss (CHL) a child has due to a given episode of OME. Given this association, the goal of this work was to determine how well CHL could be estimated directly from WAI in ears with OME.Design: Sixty-three ears from a previously published study on OME (ages 9 months to 11 years, 2 months) were grouped based on effusion volume (full, partial, or clear) determined during tympanostomy tube placement surgery and compared with age-matched normal control ears. Audiometric thresholds were obtained for a subset of the 34 ears distributed across the four groups. An electrical-analog model of earcanal acoustics and middle-ear mechanics was fit to the measured WAI from individual ears. Initial estimates of CHL were derived from either (1) average absorbance or (2) the model component thought to represent damping in the ossicular chain. Results:The analog model produced good fits for all effusion-volume groups. The two initial CHL estimates were both well correlated (87% and 81%) with the pure-tone average hearing thresholds used to define the CHL. However, in roughly a third of the ears (11/34), the estimate based on damping was too large by nearly a factor of two. This observation motivated improved CHL estimates. Conclusions:Our CHL estimation method can estimate behavioral audiometric thresholds (CHL) within a margin of error that is small enough to be clinically meaningful. The importance of this finding is increased by the challenges associated with behavioral audiometric testing in pediatric populations, where OME is the most common. In addition, the discovery of two clusters in the damping-related CHL estimate suggests the possible existence of two distinctly different types of ears: pressure detectors and power detectors.

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“…The model ear-canal input impedance falseZec is related to its middle-ear impedance falseZme by elements of the ear-canal transmission matrix (see Lewis & Neely 2015):…”

Section: Methodsmentioning

confidence: 99%

“…The nonuniform transmission line is modeled as six concatenated truncated-cone sections. The transmission line is implemented numerically as a lossless two-port transmission matrix (see Lewis & Neely 2015).…”

Section: Ear-canal and Middle-ear Modelmentioning

confidence: 99%

Conductive Hearing Loss Estimated From Wideband Acoustic Immittance Measurements in Ears With Otitis Media With Effusion

Merchant

Neely

2022

Ear &Amp; Hearing

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“…An unavoidable consequence, however, is that non-uniformities between the measurement location and the tympanic membrane contribute to the plane-wave reflectance. Avoiding these contributions requires compensating for the nonuniform ear canal [e.g., using a transmission-line model to obtain the impedance at or closer to the tympanic membrane (Lewis and Neely, 2015)], for which accurate knowledge of ear-canal geometry is needed. Our results show that the assumption of a uniform ear canal is often inaccurate for this application.…”

Section: Discussionmentioning

confidence: 99%

On the calculation of reflectance in non-uniform ear canals

Nørgaard

Charaziak

Shera

2019

The Journal of the Acoustical Society of America

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Ear-canal reflectance is useful for quantifying the conductive status of the middle ear because it can be measured non-invasively at a distance from the tympanic membrane. Deriving the ear-canal reflectance requires decomposing the total acoustic pressure into its forward-and reversepropagating components. This decomposition is conveniently achieved using formulas that involve the input and characteristic impedances of the ear canal. The characteristic impedance is defined as the ratio of sound pressure to volume flow of a propagating wave and, for uniform waveguides, the plane-wave characteristic impedance is a real-valued constant. However, in non-uniform waveguides, the characteristic impedances are complex-valued quantities, depend on the direction of propagation, and more accurately characterize a propagating wave in a non-uniform ear canal. In this paper, relevant properties of the plane-wave and spherical-wave characteristic impedances are reviewed. In addition, the utility of the plane-wave and spherical-wave reflectances in representing the reflection occurring due to the middle ear, calibrating stimulus levels, and characterizing the emitted pressure in simulated non-uniform ear canals is investigated and compared.

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“…This simple model provides a useful description of the EC longitudinal sound field and provides a basis for predictions in real ear canals. Voss et al, 2000;Keefe et al, 1994;Stepp and Voss, 2005;Lewis and Neely, 2015;Feeney et al, 2017). In the reverse-stimulation case, where a displacement source moves the ossicles and the TM, the EC sound pressure distribution is independent of Z ME (see model description in the Appendix).…”

Section: Model Predictions Of Longitudinal P Z Variations In Experimental Preparationmentioning

confidence: 99%

Sound pressure distribution within human ear canals: II. Reverse mechanical stimulation

Ravicz

Cheng

Rosowski

2019

The Journal of the Acoustical Society of America

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This work is part of a study of the interactions of ear canal (EC) sound with tympanic membrane (TM) surface displacements. In human temporal bones, the ossicles were stimulated mechanically “in reverse” to mimic otoacoustic emissions (OAEs), and the sound field within the ear canal was sampled with 0.5–2 mm spacing near the TM surface and at more distal locations within the EC, including along the longitudinal EC axis. Sound fields were measured with the EC open or occluded. The reverse-driven sound field near the TM had larger and more irregular spatial variations below 10 kHz than with forward sound stimulation, consistent with a significant contribution of nonuniform sound modes. These variations generally did not propagate more than ∼4 mm laterally from the TM. Longitudinal sound field variations with the EC open or blocked were consistent with standing-wave patterns in tubes with open or closed ends. Relative contributions of the nonuniform components to the total sound pressure near the TM were largest at EC natural frequencies where the longitudinal component was small. Transverse variations in EC sound pressure can be reduced by reducing longitudinal EC sound pressure variations, e.g., via reducing reflections from occluding earplugs.

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Non-invasive estimation of middle-ear input impedance and efficiency

Cited by 20 publications

References 47 publications

Conductive Hearing Loss Estimated From Wideband Acoustic Immittance Measurements in Ears With Otitis Media With Effusion

Conductive Hearing Loss Estimated From Wideband Acoustic Immittance Measurements in Ears With Otitis Media With Effusion

On the calculation of reflectance in non-uniform ear canals

Sound pressure distribution within human ear canals: II. Reverse mechanical stimulation

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