Middle Ear Transfer Function Research Articles

Vibroplasty combined with tympanic membrane reconstruction in middle ear ventilation disorders

Although the Vibrant Soundbridge is one of the most frequently used active middle ear implants, data regarding how middle ear ventilation disorders may affect the transmission behavior of its floating mass transducer are still insufficient. Studies involving coupling the floating mass transducer to the stapes head are particularly lacking.This temporal bone study evaluated the influence of simulated middle ear ventilation disorders on the middle ear transfer function in the reconstructed middle ear. The middle ear transfer function was measured using Laser Doppler Vibrometry after vibroplasty onto the stapes head, with or without tympanic membrane reconstruction. Middle ear ventilation disorders were simulated through changes in static pressure via the external ear channel with a maximum pressure of +3 kPa. Slice thickness of tympanic membrane reconstruction material was measured using micro-CT.When the reconstructed ossicular chain and the reconstructed tympanic membrane were mechanically excited by the floating mass transducer under conditions of ambient static pressure, the transmission behavior was found to be independent of the type of tissue used. Increase in static pressure up to +3 kPa caused maximum low frequency transmission loss of 15 dB when elastic grafts were used and 5 dB when stiff tissue was inserted. At high frequencies, measured loss of up to 5 dB was relatively independent of the tissue stiffness.Increase in static pressure led to displacement of the tissues towards the vestibulum and caused stiffening, especially of the annular ligament. Stiffening-induced transmission losses were mainly found at low frequencies and could not be compensated by the floating mass transducer in this range. Above 1300 Hz, the continuous force spectrum of the actuator sufficiently protected against loss of amplitude. To minimize postoperative transmission loss due to persisting ventilation disorders, choosing a very stiff tympanic membrane reconstruction material seems to be appropriate.

Assessment of sound transfer function of middle ear based on cochlear microphonic (CM) evoked by direct excitation of ossicles

Assessment of sound transfer function of middle ear based on cochlear microphonic (CM) evoked by direct excitation of ossicles

A study of transfer function of human middle ear by bone conduction

Vibration of tympanic membrane induced by sound is transmitted to a cochlea via middle-ear ossicular chain and stimulates an auditory nerve. Hearing sensation produced by sound is described as air conduction. Vibration of a skull induced by vocal sound is also transmitted to a cochlea. Hearing sensation produced by vibration of a skull is described as bone conduction. Therefore, human vocal sound is perceived by means of two pathways, air and bone conduction. In the present study, the roll of the ossicular chain of bone conduction is analyzed numerically by using a technique of multibody dynamics. The numerical model of the ossicular chain is created precisely by using pictures of computerized axial tomography scan. The vibrational responses of the ossicular chain and the force transmitted to a cochlea induced by the stimuli of air and bone conduction ware calculated. The magnitude of the force induced by the bone conduction was about one third of that induced by the air conduction.

Feasibility Study of a Mechanical Real-Time Feedback System for Optimizing the Sound Transfer in the Reconstructed Middle Ear

To evaluate electromechanical excitation as an alternative excitation mode for middle ear transfer function (METF) measurements as well as real-time feedback in prosthetic ossicular reconstruction. In eight human cadaveric temporal bones, the ossicular chain was excited using acoustic and mechanical (floating mass transducer, FMT) stimulation to determine the METF. After disconnecting the ossicular chain and reconstruction with partial or total prosthesis the METFs were measured again. Continuous FMT stimulation was then applied to improve the prosthesis' position using real-time feedback of the METF. Mechanical stimulation of ossicular vibration showed characteristic differences to acoustic excitation resulting from the force characteristics of the FMT. Furthermore, the interspecimen METF variability was greater with electromechanical than acoustic stimulation because of interspecimen variability in the FMT coupling conditions. When the METF with FMT excitation was used as a real-time feedback tool, a measurable improvement in the quality of ossicular reconstruction could be achieved. Mechanical excitation is an effective and suitable alternative stimulation method in experimental METF measurements. The system provides real-time feedback for ossicular reconstruction in the experimental setting. Some influencing factors still need to be distinguished for reliable measurements. However, the method does not yet meet the requirements for clinical application as an intraoperative, real-time monitoring tool. However, the system could be an excellent model for high-end cadaveric temporal bone training in ossiculoplasty.

Development of intra-operative assessment system for ossicular mobility and middle ear transfer function

Objective measurements of the ossicular mobility have not been commonly performed during the surgery, and the assessment of ossicular mobility is made by palpation in most cases. Palpation is inherently subjective and may not always be reliable, especially in milder degrees of ossicular fixation and in the case of multiple fixation. Although several devices have been developed to quantitatively measure the ossicular mobility during surgery, they have not been widely used. In this study, a new system with a hand-held probe which enables intraoperative quantitative measurements of ossicular mobility has been developed. This system not only measures the ossicular mobility, but also investigates “local” transmission characteristics of the middle ear by directly applying vibration to the ossicles and measuring cochlear microphonic. The basic performance of this system was confirmed by measuring the mobility of artificial ossicles and cochlear microphonics in an animal experiment. Our system may contribute to selection of a better surgical method and reducing the risks of revision surgery.

A model and experimental approach to the middle ear transfer function related to hearing in the humpback whale (Megaptera novaeangliae).

At present, there are no direct measures of hearing for any baleen whale (Mysticeti). The most viable alternative to in vivo approaches to simulate the audiogram is through modeling outer, middle, and inner ear functions based on the anatomy and material properties of each component. This paper describes a finite element model of the middle ear for the humpback whale (Megaptera novaeangliae) to calculate the middle ear transfer function (METF) to determine acoustic energy transmission to the cochlea. The model was developed based on high resolution computed tomography imaging and direct anatomical measurements of the middle ear components for this mysticete species. Mechanical properties for the middle ear tissues were determined from experimental measurements and published values. The METF for the humpback whale predicted a better frequency range between approximately 15 Hz and 3 kHz or between 200 Hz and 9 kHz based on two potential stimulation locations. Experimental measures of the ossicular chain, tympanic membrane, and tympanic bone velocities showed frequency response characteristics consistent with the model. The predicted best sensitivity hearing ranges match well with known vocalizations of this species.

Function, Applicability, and Properties of a Novel Flexible Total Ossicular Replacement Prosthesis With a Silicone Coated Ball and Socket Joint.

A total ossicular replacement prosthesis (TORP) with a silicone coated ball and socket joint (BSJ) is able to compensate pressure changes and therefore provide better sound transmission compared with rigid prostheses. Dislocation and extrusion are known complications after TORP reconstruction, leading to revisions and recurrent hearing loss. Poor aeration of the middle ear, scar tension, and static pressure variations in conjunction with rigid prosthesis design causes high tension at the implant coupling points. A novel TORP prototype with a silicone coated BSJ has been developed. Experimental measurements were performed on nine fresh cadaveric human temporal bones of which five were used for a comparison between rigid TORP and flexible TORP tympanoplasty. The middle ear transfer function was measured at ambient pressure and at 2.5 kPa, both positive and negative pressure, applied in the ear canal. The flexible TORP design yields a better transmission of sound after implantation and at negative pressure inside the tympanic cavity, compared with rigid TORP. In average, it provides an equivalent sound transfer like the intact middle ear. At positive pressure, the flexible TORP performs slightly worse. Both performed worse than the intact middle ear, which is related to an uplifting of the prostheses. The findings may be considered preliminary as this experimental study was limited to just one of the many different possible situations of tympanoplasty and it involved a small sample size. Nevertheless, the results with the flexible TORP were promising and could encourage further investigations on such prostheses.

Impedances of the inner and middle ear estimated from intracochlear sound pressures in normal human temporal bones

For almost a decade, we have measured intracochlear sound pressures evoked by air conducted (AC) sound presented to the ear canal in many fresh human cadaveric specimens. Similar measurements were also obtained during round window (RW) mechanical stimulation in multiple specimens. In the present study, we use our accumulated data of intracochlear pressures and simultaneous velocity measurements of the stapes or RW to determine acoustic impedances of the cochlear partition, RW, and the leakage paths from scala vestibuli and scala tympani, as well as the reverse middle ear impedance. With these impedances, we develop a computational lumped-element model of the normal ear that illuminates fundamental mechanisms of sound transmission.To calculate the impedances for our model, we use data that passes strict inclusion criteria of: (a) normal middle-ear transfer function defined as the ratio of stapes velocity to ear-canal sound pressure, (b) no evidence of air within the inner ear, and (c) tight control of the pressure sensor sensitivity. After this strict screening, updated normal means, as well as individual representative data, of ossicular velocities and intracochlear pressures for AC and RW stimulation are used to calculate impedances. This work demonstrates the existence and the value of physiological acoustic leak impedances that can sometimes contribute significantly to sound transmission for some stimulation modalities. This model allows understanding of human sound transmission mechanisms for various sound stimulation methods such as AC, RW, and bone conduction, as well as sound transmission related to otoacoustic emissions.

Intracochlear pressure measurements during acoustic shock wave exposure

IntroductionInjuries to the peripheral auditory system are among the most common results of high intensity impulsive acoustic exposure. Prior studies of high intensity sound transmission by the ossicular chain have relied upon measurements in animal models, measurements at more moderate sound levels (i.e. < 130 dB SPL), and/or measured responses to steady-state noise. Here, we directly measure intracochlear pressure in human cadaveric temporal bones, with fiber optic pressure sensors placed in scala vestibuli (SV) and tympani (ST), during exposure to shock waves with peak positive pressures between ∼7 and 83 kPa. MethodsEight full-cephalic human cadaver heads were exposed, face-on, to acoustic shock waves in a 45 cm diameter shock tube. Specimens were exposed to impulses with nominal peak overpressures of 7, 28, 55, & 83 kPa (171, 183, 189, & 192 dB pSPL), measured in the free field adjacent to the forehead. Specimens were prepared bilaterally by mastoidectomy and extended facial recess to expose the ossicular chain. Ear canal (EAC), middle ear, and intracochlear sound pressure levels were measured with fiber-optic pressure sensors. Surface-mounted sensors measured SPL and skull strain near the opening of each EAC and at the forehead. ResultsMeasurements on the forehead showed incident peak pressures approximately twice that measured by adjacent free-field and EAC entrance sensors, as expected based on the sensor orientation (normal vs tangential to the shock wave propagation). At 7 kPa, EAC pressure showed gain, calculated from the frequency spectra, consistent with the ear canal resonance, and gain in the intracochlear pressures (normalized to the EAC pressure) were consistent with (though somewhat lower than) previously reported middle ear transfer functions. Responses to higher intensity impulses tended to show lower intracochlear gain relative to EAC, suggesting sound transmission efficiency along the ossicular chain is reduced at high intensities. Tympanic membrane (TM) rupture was observed following nearly every exposure 55 kPa or higher. ConclusionsIntracochlear pressures reveal lower middle-ear transfer function magnitudes (i.e. reduced gain relative to the ear canal) for high sound pressure levels, thus revealing lower than expected cochlear exposure based on extrapolation from cochlear pressures measured at more moderate sound levels. These results are consistent with lowered transmissivity of the ossicular chain at high intensities, and are consistent with our prior report measuring middle ear transfer functions in human cadaveric temporal bones with high intensity tone pips.

Experimental Simulation of Clinical Borderline Situations in Temporal Bone Specimens After Ossiculoplasty.

One reason for insufficient hearing improvement with a distinct air-bone gap after ossiculoplasty with implantation of partial or total ossicular replacement prostheses can be the dislocation or minimal shifting of the prosthesis. The aim of this study was the simulation of common clinical borderline situations with minimal shifting of the prosthesis in temporal bone specimens after ossiculoplasty. It was furthermore the goal to identify these specific situations through imaging by cone beam computed tomography (cbCT) and direct visual inspection using the operation microscope. Additionally, the functional status was evaluated using laser-Doppler vibrometry (LDV). We used a total of four temporal bone specimens for this study. A reconstruction with a partial ossicular replacement prostheses was performed in three specimens and with a total ossicular replacement prostheses in one specimen, with good initial acoustic properties. Subsequently, one specific type of prosthesis failure was simulated in each specimen, respectively, by minimally shifting, tilting, or bending the prostheses from their initial positions. These changes were introduced step-by-step until a borderline situation just short of complete acoustic decoupling was reached. Each step was examined using both LDV and cbCT and observed through the operation microscope. LDV was able to quantify the mechanic function of the ossicular chain after most of the manipulation steps by demonstrating the effect of any shifting of the prosthesis on the middle ear transfer function. However, in some situations, the middle ear transfer function was better with a visually more advanced failure of the prosthesis. In addition, cbCT showed most of the steps with excellent resolution and was able to delineate changes in soft tissue (e.g., cartilage covering). cbCT seems to be a promising imaging technique for middle ear problems. As cbCT and LDV exhibited slightly different advantages and disadvantages regarding the demonstration of borderline situations, the combination of both techniques allowed for a more precise evaluation of middle ear reconstructions. Knowledge of the specific characteristics of these methods and their possible combination might help otologists and otosurgeons to refine indications for revision surgery and improve their personal patient counseling.

Effects of middle ear quasi-static stiffness on sound transmission quantified by a novel 3-axis optical force sensor

BackgroundIntra-operative quantification of the ossicle mobility could provide valuable feedback for the current status of the patient's conductive hearing. However, current methods for evaluation of middle ear mobility are mostly limited to the surgeon's subjective impression through manual palpation of the ossicles. This study investigates how middle ear transfer function is affected by stapes quasi-static stiffness of the ossicular chain. The stiffness of the middle ear is induced by a) using a novel fiber-optic 3-axis force sensor to quantify the quasi-static stiffness of the middle ear, and b) by artificial reduction of stapes mobility due to drying of the middle ear. MethodsMiddle ear transfer function, defined as the ratio of the stapes footplate velocity versus the ear canal sound pressure, was measured with a single point LDV in two conditions. First, a controlled palpation force was applied at the stapes head in two in-plane (superior-inferior or posterior-anterior) directions, and at the incus lenticular process near the incudostapedial joint in the piston (lateral-medial) direction with a novel 3-axis PalpEar force sensor (Sensoptic, Losone, Switzerland), while the corresponding quasi-static displacement of the contact point was measured via a 3-axis micrometer stage. The palpation force was applied sequentially, step-wise in the range of 0.1–20 gF (1–200 mN). Second, measurements were repeated with various stages of stapes fixation, simulated by pre-load on the stapes head or drying of the temporal bone, and with severe ossicle immobilization, simulated by gluing of the stapes footplate. ResultsSimulated stapes fixation (forced drying of 5–15 min) severely decreases (20–30 dB) the low frequency (<1 kHz) response of the middle ear, while increasing (5–10 dB) the high frequency (>4 kHz) response. Stapes immobilization (gluing of the footplate) severely reduces (20–40 dB) the low and mid frequency response (<4 kHz) but has lesser effect (<10 dB) at higher frequencies. Even moderate levels of palpation force (<3gF, <30 mN), regardless of direction, have negative effect (10–20 dB) on the low frequency (<2 kHz) response, but with less significant (5–10 dB) effect at higher frequencies. Force-displacement measurements around the incudostapedial joint showed quasi-static stiffness in the range of 200–500 N/m for normal middle ears, and 1000–2500 N/m (5–8-fold increase) after artificially (through forced drying) reducing the middle ear transfer function with 10–25 dB at 1 kHz. ConclusionEffects of the palpation force level and direction, as well as stapes fixation and immobilization have been analyzed based on the measurement of the stapes footplate motion, and controlled application of 3D force and displacement.

Middle ear reconstruction with a flexible prosthesis

Abstract The middle ear plays a crucial role in the quality of hearing. This complex construct performs different tasks like the protection against large air pressure input, the transmission of sound and its adaption to the inner ear impedance. Traumas, erosion by chronic otitis media or cholesteatoma, as well as other degenerative or damaging diseases, are reasons for a necessary reconstruction of specific middle ear structures. The reconstruction of the ossicular chain is very often performed by using rigid ossicular replacement prostheses made out of titanium, ceramics or bone. Tilting and dislocation of these passive implants are some of the known complications after middle ear surgery. They are related to loads at the implant coupling points in response to a tension change in the middle ear. The healing process, scar tension and ventilation problems are possible causes. To increase the sound transmission quality of total reconstructions and safety in case of pressure dependent movement of the tympanic membrane, a novel flexible total ossicular replacement prosthesis (TORP) with a silicone coated ball joint prototype was developed and investigated. Besides measurements of first middle ear transfer functions of temporal bones, the mechanical properties of the flexible TORP were examined with stress relaxation investigations. The novel silicone coated ball and socket joint TORP provides a sound transfer equivalent to the intact human middle ear at normal pressure and negative pressure in the middle ear. Together with the low stiffness values at an anatomically typical deflection of about 500 μm the prevention of a stiffening of the stapes annular ligament could be approved. Thus, improved acoustic transmission quality and reconstruction stability in comparison to common rigid titanium TORP could be determined. Nevertheless, further design improvements should be accomplished. The demonstrated flexible TORP can solve some common problems in middle ear reconstruction.

The Impact of a Cochlear Implant Electrode Array on the Middle Ear Transfer Function.

As a treatment for partial deafness with residual hearing in the lower frequency range, the combined acoustic and electric stimulation of the cochlea has become widespread. Acoustic stimulation is provided by a hearing aid's airborne sound and the electric stimulation by a cochlear implant electrode array, which may be inserted through the round window or a cochleostomy. To take advantage of that concept, it is essential to preserve residual hearing after surgery. Therefore, the intracochlear electrode array should not compromise the middle ear vibration transmission. This study investigates the influence of different electrode types and insertion paths on the middle ear transfer function and the inner ear fluid dynamics. Sound-induced oval and round window net volume velocities were calculated from vibration measurements with laser vibrometers on six nonfixated human temporal bones. After baseline measurements in the "natural" condition, a cochleostomy was drilled and closed with connective tissue. Then, four different electrode arrays were inserted through the cochleostomy. Afterwards, they were inserted through the round window while the cochleostomy was patched again with connective tissue. After having drilled a cochleostomy and electrode insertion, no systematic trends in the changes of oval and round window volume velocities were observed. Nearly all changes of middle ear transfer functions, as well as oval and round window volume velocity ratios, were statistically insignificant. Intracochlear electrode arrays do not significantly increase cochlear input impedance immediately after insertion. Any changes that may occur seem to be independent of electrode array type and insertion path.

A comparative study of MED-EL FMT attachment to the long process of the incus in intact middle ears and its attachment to disarticulated stapes head

The Vibrant Soundbridge© (VSB) active middle-ear implant provides an effective treatment for mild-to-severe sensorineural hearing loss in the case of normal middle ear anatomy and mixed hearing loss in middle ear malformation. The VSB floating mass transducer (FMT), with proper couplers, can be installed on various structures of the ossicular chain, e.g., the short and long process of the incus, the stapes head, and the stapes footplate. A long process (LP) coupler is most commonly used for FMT attachment to the long process of the incus with intact ossicular chain, while CliP and Bell couplers are two standardized and reliable methods for FMT attachment to the stapes head with missing incus and malleus. However, the difference and relationship of the vibration properties among these three FMT couplers remain unclear.In the present study, the stapes footplate velocity responses of the LP, CliP, and Bell couplers have been investigated in eight fresh temporal bones (TBs) to evaluate the vibration properties of these three couplers. Normal and reconstructed middle ear transfer functions (METFs) were determined from laser Doppler vibrometer (LDV) measurements. A mastoidectomy and a posterior tympanotomy were performed to expose the ossicular chain. The METFs of the normal middle ear and middle ear with LP-FMT-coupler were compared under acoustic stimulation, thus the mass effect of the FMT with LP coupler was evaluated. Additional comparisons were made between the stapes footplate vibrations of the LP-FMT-coupler (with the intact ossicular chain at the long process of the incus), CliP-FMT-coupler and Bell-FMT-coupler on the stapes head (after incus and malleus removed) under active electromechanical stimulation. After the installation of CliP-FMT-coupler and Bell-FMT-coupler to the middle ear, the average velocity amplitude of the stapes footplate, comparing to the LP-FMT-coupler, was about 15 dB higher between 1 and 6 kHz, and 10 dB lower at about 0.5 kHz. Quantitatively, there was no significant difference between the CliP-FMT-coupler and Bell-FMT-coupler.According to our study, installation of CliP-FMT-coupler or Bell-FMT-coupler on the stapes head provides considerable improvement of the middle ear mechanical and functional responses, comparing with the LP-FMT-coupler in the temporal bone experiments. Moreover, the installation of the Bell-FMT-coupler to the stapes head produces essentially the same footplate velocity responses in comparison to the CliP-FMT-coupler.

Nonlinear response of human middle ear to high level sound

The human middle ear functions as an acoustic transformer that converts environmental sound energy into mechanical drive to stimulate the cochlea for hearing. This transformation has been demonstrated to be linear at sound levels at least as high as 125 dB. While this behavior can be expected to breakdown at some higher level, that level has not been demonstrated. In this study, we use cadaveric human ears to study middle ear nonlinear responses to high levels of sound. Tones between 200 and 10000 Hz with levels as high as 160 dB SPL are generated by a customized horn speaker and delivered to the ear canal opening. Sound pressure levels near the tympanic membrane surface are monitored by a calibrated pressure sensor. Simultaneously, Laser Doppler Vibrometry is used to record sound induced vibrations of the Umbo, in the center of the tympanic membrane, and the stapes, at the interface of the middle and inner ear. These data allow us to calculate the middle ear transfer function: the ratio of the stapes to umbo vibration. We use these measurements to investigate what is the threshold sound pressure above which the human middle ear response is no longer linear.

Effect of fixation of superior mallear ligament and anterior mallear ligament on the middle ear transfer function-finite element modeling

Objective:To study the effect of fixation of superiormallear ligament (SML) and anterior mallear ligament(AML) on the middle ear transfer function. Method:A middle ear finite element model was established using micro-CT scanning from an adult temporal bone with normal middle ear structure. And the fixation model of SML and AML were established by changing its Young's modulus. Calculation of fixation and detachment of the two ligaments on the middle ear transfer function. Result:Displacement of tympanic membrane and stapes footplate was decreased significantly in case of fixation in both AML and SML, especially in the low frequency region.The SML fixation increased the amplitude of the stapes footplate by 3 dB between 1-2 kHz. In case of SML fixation along and both the SML and AML all fixation, the vibration of the stapes footplate was decreased obviously by 4 dB and 6 dB, respectively. By contrast, detachment of the SML and AML have little effect on the displacement of the stapes footplate. Conclusion:It is different that the effect of AML and SML on the vibration of the tympanic membrane and the stapes footplate. The SML fixation decreased the displacement of tympanic membrane and stapes footplate. Both the SML and SML all fixated decrease the stapes footplate significantly.But, there is little effect of the detachment of SML and AML on the displacement of the stapes footplate.

A New Intraoperative Real-time Monitoring System for Reconstructive Middle Ear Surgery: An Experimental and Clinical Feasibility Study.

Electromagnetical excitation of ossicular vibration is suitable for middle ear transmission measurements in the experimental and clinical setting. Thereby, it can be used as a real-time monitoring system for quality control in ossiculoplasty. Positioning and coupling of middle ear prosthesis are a precondition for good postoperative hearing results, but at the same time completely dependent upon the surgeon's subjective judgment during surgery. We evaluated an electromagnetically driven measurement system that enables for in vitro and in vivo transmission measurements and thus can be used as a real-time monitoring tool in ossicular reconstruction. For electromagnetical excitation a magnet was placed on the umbo of the malleus handle and driven by a magnetic field. The induced stapes displacement was picked up by laser Doppler vibrometry on the footplate. Measurements were performed on the intact ossicular chain in five cadaveric temporal bones and during five cochlear implant surgeries. Additionally, two ossiculoplasties were performed under real-time transmission feedback with the monitoring system. Experimentally, the equivalent sound pressure level of the electromagnetic excitation was about 70 to 80 dB which is 10 to 20 dB less than the acoustic stimulation. In the intraoperative setup the generated stapes displacements were about 5 to 20 dB smaller compared with the temporal bone experiments. Applied as real-time feedback system, an improvement in the middle ear transfer function of 4.5 dB in total and 20 dB in partial ossicular reconstruction were achieved. The electromagnetical excitation and measurement system is comparable to the gold standard with acoustical stimulation in both, the experimental setup in temporal bones as well as in vivo. The technical feasibility of the electromagnetical excitation method has been proven and it is shown that it can be used as a real-time monitoring system for ossiculoplasty in the operation room.

Impact of Prosthesis Length on Tympanic Membrane's and Annular Ligament's Stiffness and the Resulting Middle Ear Sound Transmission.

Prosthesis' length creates tension in ossicular reconstructions, which directly effects the middle ear sound transmission. Relatively long prostheses are often used to stabilize the middle ear reconstruction to prevent dislocation. Thereby, tension on the flexible components such as the tympanic membrane (TM) and the annular ligament (AL) is increased. Only little is known on the amount of displacement-related stiffening of the TM and AL, as well as the consecutive reduction in middle ear transfer function (METF). An expandable total ossicular replacement prosthesis was tensionfree inserted in nine cadaveric temporal bones between the malleus handle and the stapes footplate. Upon heat activation the prosthesis was lengthened, thus inducing tension on the reconstruction. The METF was assessed before and after elongation. TM's and AL's stiffness were determined by measuring their force-displacement characteristics. Upon activation the prostheses were elongated between 50 and 200 μm. A frequency-dependent METF reduction was measured with a decrease of 5 to 25 dB below 1.0 kHz. At frequencies >2.0 kHz the reduction was less prominent or the METF showed even an improvement of up to 10 dB. TM's stiffness remained constant during the elongation-induced displacement, whereas the AL's stiffness increased. The METF reduction below 1.0 kHz correlated with the increasing AL's stiffness. Tension has a significant impact on the METF after middle ear reconstruction. As little tension as possible should be used to enable best sound transmission. Stabilization of prosthesis should be achieved with dislocation devices to ensure secure coupling to the ossicular remnants without creating additional tension.

Multi-species Baleen Whale audiogram modelling

In this research, we produced model audiograms for two Mysticetes (baleen whales) that are among the species most likely to be subject to impacts from common lower frequency anthropogenic sound sources deployed in the oceans. These models are needed for species-specific risk assessments for hearing impacts, for determining optimal signals for playback experiments, and for determining effective electrode and sound source placements for auditory brainstem response (ABR) measures in live stranded whales. We employed micro and UHRCT, dissection, and histology of minke (Balaenoptera acutorostrata) and humpback (Megaptera novaeangliae) heads and ears to calculate inner ear frequency maps for determining total hearing range, the frequency of peak sensitivity, and the probable frequency of NIHL liability (“notch”). The anatomically derived data were then combined with direct measures via nanoindentation of middle ear stiffness, Young’s modulus, frequency response, and inner ear stiffness to determine the middle ear transfer function and basilar membrane stiffness gradients. FEM simulations were employed to further explore the responsivity of the tympanum and middle ear ossicular chain. In order to test the validity of the model techniques, model audiograms were produced also for two odontocetes, the bottlenose dolphin and the harbor porpoise, and compared with well-established behaviorally obtained audiograms for these species. [This research was supported by the LMR and JIP marine research programs.]

Wideband Acoustic Immittance: Normative Study and Test-Retest Reliability of Tympanometric Measurements in Adults.

The purpose of this study was to present normative data of tympanometric measurements of wideband acoustic immittance and to characterize wideband tympanograms. Data were collected in 84 young adults with strictly defined normal hearing and middle ear status. Energy absorbance (EA) was measured using clicks for 1/12-octave frequencies (0.236 to 8 kHz), with the ear canal air pressure systematically varied (+200 to -300 daPa). In 40 ears, 7 consecutive trials and a trial of clinical 226-Hz acoustic admittance (Ya) tympanometry followed. A cavity test was also conducted. From the wideband EA tympanogram, several EA spectrums and EA tympanograms were derived. Descriptive statistics were performed, and population parameters were estimated. The immediate test-retest reliability was excellent. Effects of ear canal air pressure on EA were examined comprehensively. Differences in EA between tympanometric and ambient-pressure measurements were significant. Single-frequency EA tympanograms exemplified for half-octave frequencies were contrasted. The bandpass EA tympanogram, 0.236- and 1-kHz EA and Ya tympanograms, and 226-Hz Ya tympanogram were compared in 9 variables. This study established a database of wideband tympanograms in healthy adults. The data analyses will promote our understanding of the middle ear transfer function. These data will serve as a reference for further studies in clinical populations.