Mathematical modeling of a probe-tube microphone

The middle-ear input admittance relates sound power into the middle ear (ME) and sound pressure at the tympanic membrane (TM). ME input admittance was measured in the chinchilla ear canal as part of a larger study of sound power transmission through the ME into the inner ear. The middle ear was open, and the inner ear was intact or modified with small sensors inserted into the vestibule near the cochlear base. A simple model of the chinchilla ear canal, based on ear canal sound pressure measurements at two points along the canal and an assumption of plane-wave propagation, enables reliable estimates of Y(TM,) the ME input admittance at the TM, from the admittance measured relatively far from the TM. Y(TM) appears valid at frequencies as high as 17 kHz, a much higher frequency than previously reported. The real part of Y(TM) decreases with frequency above 2 kHz. Effects of the inner-ear sensors (necessary for inner ear power computation) were small and generally limited to frequencies below 3 kHz. Computed power reflectance was ~0.1 below 3.5 kHz, lower than with an intact ME below 2.5 kHz, and nearly 1 above 16 kHz.

Section: Predict Y Tm From Y Ec Using Estimates Of Ec Coupling Lengthmentioning

confidence: 99%

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confidence: 99%

Chinchilla middle-ear admittance and sound power: High-frequency estimates and effects of inner-ear modifications

Ravicz

Rosowski

2012

“…The decision not to include these membranes was based on observations that presence or absence of a membrane at the interface between the fluid and air did not impact our measured results and we wanted to keep the model as simple as possible. 4 The lossy transmission-line models of tube segments that we use were first described by Egolf, 1977, and adapted for fluid filled tubes by Dickens, 1986, as follows: γ is ratio of specific heats of the fluid medium, c is the speed of sound in water, ρ is the density of water, κ is the thermal conductivity of water, μ is the absolute viscosity and c p is the specific heat.…”

Section: B Model Of the Sc With Dehiscencementioning

confidence: 99%

“…The model consists of three blocks. The first block consists of two two-port tube models (Egolf, 1977) that account for the lateral branch of the SC including the ampulla of the SC (Z amp ) and the SC segment lateral to the dehiscence (Z lsc ). In parallel with these two ports is the second block, another set of two ports which model sound flow through the medial branch of the SC, first the wide segment (Z mscw ) and then the narrower segment (Z msc ).…”

Section: A Anatomical Reconstructionmentioning

confidence: 99%

A mechano-acoustic model of the effect of superior canal dehiscence on hearing in chinchilla

Songer

Rosowski²

2007

Superior canal dehiscence (SCD) is a pathological condition of the ear that can cause a conductive hearing loss. The effect of SCD (a hole in the bony wall of the superior semicircular canal) on chinchilla middle-and inner-ear mechanics is analyzed with a circuit model of the dehiscence. The model is used to predict the effect of dehiscence on auditory sensitivity and mechanics. These predictions are compared to previously published measurements of dehiscence related changes in chinchilla cochlear potential, middle-ear input admittance and stapes velocity. The comparisons show that the model predictions are both qualitatively and quantitatively similar to the physiological results for frequencies where physiologic data are available. The similarity supports the third-window hypothesis of the effect of superior canal dehiscence on auditory sensitivity and mechanics and provides the groundwork for the development of a model that predicts the effect of superior canal dehiscence syndrome on auditory sensitivity and mechanics in humans.

“…4 A load impedance Z L is matched to a source impedance Z S when Z L and Z S are conjugates: Z L ϭZ S *. 5 The reflectance can be computed from the characteristic impedance of a tube that includes thermal and viscous losses ͑see, e.g., Egolf, 1977͒ with no loss of generality. 6 The power utilization ratio can be expressed in terms of R T and the reflectance looking out the external ear R E .…”

mentioning

confidence: 99%

Sound-power collection by the auditory periphery of the mongolian gerbil Meriones unguiculatus. II. External-ear radiation impedance and power collection

Ravicz

Rosowski

Voigt

1996

Acoustic power flow into the external and middle ear of the gerbil is computed from acoustic measurements and models of the external ear and used to predict the behavioral auditory threshold. The external-ear radiation impedance from the tympanic ring ZE measured in six gerbil ears with a calibrated acoustic source at frequencies from 10 Hz to 18 kHz is mass dominated below about 8 kHz, with a mean mass of 2720 kg/m4. ZE shows resonant behavior near 8 and 14 kHz. The frequency dependence of ZE is similar to that measured in cat, chinchilla, and models of the human external ear, but the mass and the resonant frequencies are higher. The power utilization ratio (PUR) computed from ZE and measurements of the middle-ear input impedance ZT presented previously [Ravicz et al., J. Acoust. Soc. Am. 92, 157-177 (1992)] suggests that appreciable power is transmitted to the middle ear only above 1.5 kHz. Mathematical external-ear models, consisting of tube segments and conical horns that include viscous and thermal losses, were developed from anatomical dimensions to match ZE over the entire frequency range of measurement. The radiation efficiency eta R computed from the models is near unity only above 12 kHz and falls to 10(-5) as frequency decreases to 10 Hz. Predictions of the mean pressure gain from an external diffuse sound field to the tympanic membrane resemble measurements in another gerbilline species. The effective area of the ear in a diffuse sound field at the tympanic membrane EATMDF computed from PUR and eta R approaches the anatomical area of the pinna opening, 71 mm2, above 1.5 kHz and the geometric limit of lambda 2 /4 pi determined by the wavelength lambda above 12 kHz but decreases sharply below 1.5 kHz to 0.002 mm2 at 10 Hz. The diffuse-field sound pressure required to deliver 5 x 10(-17) W to the middle ear between 10 Hz and 18 kHz resembles the behavioral auditory threshold [Ryan, J. Acoust. Soc. Am. 54, 1222-1226 (1976)]. This result supports the idea that the cochlea acts as a power detector at the auditory threshold.