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High-resolution 3D morphology models of cat, gerbil, rabbit, rat and human ossicular chains are presented. The models are based on high-resolution CT measurements. The resolution of the CT images, from which the models are segmented, varies from 5.6 to 33.5 μm. Models are freely available in different formats at our website (http://www.ua.ac.be/bimef/models) for research and educational purposes.

Recently, a new signal analysis method was developed to detect small non-linear distortions in weakly non-linear systems using specially designed broadband excitation signals, i.e. odd random phase multisines. The method allows the detection and quantification of the system response, noise level and both odd and even degree nonlinear distortions over an extensive frequency range from one single short-term measurement. Here, this method is implemented in an opto-acoustical set-up to detect small non-linearities in the response of vibrating structures. Because of the highly linear response achievable with heterodyne vibrometry, it is possible to detect non-linearities in the system under test with extremely high sensitivity. Non-linear behaviour is very common in biomechanical systems, but their dynamics and thus response might change over time. This leads to measurement artifacts that cause an overestimation of the noise level. A correction algorithm can be applied to remove the effect of these time variations, so that heterodyne vibrometry also allows the detection and quantification of non-linearities in unstable biomechanical systems. In this paper the technique is demonstrated with a measurement of the non-linear distortions in the vibration of the gerbil middle ear, where the use of a non-contact optical detection method is essential to not disturb the tiny vibrating structures.

When performing phase-shifting, phase differences in a periodic intensity profile are changed, and the resulting irradiance distributions are recorded at each step. The wanted phase can be obtained from the arctangent of the ratio between two combinations of the observed irradiances, according to the phase-shifting algorithm (psa) used. There are many such combinations and thus different psas, each with specific performance and properties. We briefly discuss some error sources which might influence the performance and quality of interferometry measurements. The robustness against these error sources is strongly dependent on the psa used. Several computer simulations on all of the 84 psas were carried out to confirm which algorithms perform best in the presence of some straightforward error sources.

It has been shown that in cardiovascular risk management, stiffness of large arteries has a very good predictive value for cardiovascular disease and overall mortality. This parameter can be estimated from the pulse wave velocity (PWV) measured between the common carotid artery (CCA) (neck) and femoral (groin) artery. However, current methods to determine arterial PWV suffer from several shortcomings. In this work, we propose a novel, non-contact laser Doppler vibrometry (LDV) technique, for evaluating carotid PWV, directly from CCA. This approach was extensively validated in vitro, and here it is tested for the first time on a small group of young healthy volunteers. Our preliminary results demonstrate that laser-based non-contact measurement of PWV is feasible, as measured PWV values are consistent with the literature. With possible clinical applications in mind, the non-contact character of the method combined with the possibility to measure carotid PWV, promises important advantages over existing methods. Moreover, measurements are straightforward and do not require intensive training.

We studied the postnatal development of the middle ear (ME) in New Zealand White rabbits. Bullae were scanned using a desktop X-ray microtomograph and 3D models of the ME ossicles as well as the tympanic ring (TR) were prepared. In 0, 1, 2 days old rabbits the ossification process was incomplete. We can therefore present quantitative data obtained from older rabbits (ages: 4–180 days) and a qualitative description at the earlier ages. For a number of the measured parameters an exponential curve could be fitted to the data, and the time constant (at which 63% of the final value was obtained) was calculated. The length of the manubrium increased rapidly in a period of about 15 postnatal days, from 1.73 mm to 4.08 mm. The distance between the tip of the malleus and the TR increased rapidly until day 30, from nearly 0 to 1.40 mm. The increase of the surface area within the TR was small as compared to inter-specimen variance, but the ratio [tympanic membrane area]/[TR area] clearly increased (from 1.00 to 1.11), with a time constant of 8.3 days. The area of the stapes footplate (FP) increased rapidly in about 15 days (from 0.72 mm2 to 1.49 mm2, time constant 4.8 days). The TR was nearly developed at birth whereas the stapes footplate was quite underdeveloped. The distance between the tip of the malleus and the incudomallear rotation axis increased rapidly until day 20 and varied between 3.47 mm and 5.00 mm. The distance between the tip of the incus and the rotation axis increased until day 133, from 1.39 mm to 1.69 mm. Our study shows that in rabbits the ME is underdeveloped at birth and that the functional geometry develops over the same time course as the ability to hear. The conical shape of the tympanic membrane (TM) is formed by retraction and growth of the manubrium, mainly during the first 40 days after birth.

We have developed a simple digital speckle pattern interferometry (DSPI) and shearography setup to measure the displacement and the corresponding strains of small complex bony structures. We choose both optical techniques because we want to obtain very small deformations (± 20 μm) of small objects (± 1cm). Furthermore full field and in situ measurements are preferred. We first use a Michelson DSPI arrangement with phase shifting. In this way we can obtain the out-of-plane displacements precisely. Second, shearography is introduced to measure the derivative of the out-ofplane displacement. In this way some intrinsic disadvantages of DSPI can be overcome. We have developed these setups to measure the out-of-plane deformations of (small) bird beaks when realistic external forces are applied. In this way, we have a full field validation measurement to which we can compare the outcome of realistic finite element models. The aim is to determine whether the shape, and not only the size, of the bird beaks are optimized to deal with the biting forces that a species encounters. This quantitative analysis will help biologists to investigate if beak morphology is adapted to feeding habits. Applying the method to the famous evolution model of the Darwin's finches will provide scientific proof of functional evolution. In this paper we will present both the DSPI and shearography setup, a comparison of the performance of both techniques on a simple deflection of a cantilever beam and the first results obtained on loaded bird beaks.

Darwins finches are a model system for studying adaptive diversification. However, despite the large body of work devoted to this system, rather little is known about the functional consequences of variation in the size and shape of bills. We test, using two methods, if natural or sexual selection, or both, has resulted in functional divergence in bill and head morphology. Firstly, we compare data on head-shape and bite-forces across nine species of Darwins finches. Secondly, we use micro-CT scans and finite-element models to test the prediction that the shape of the bill in representatives of the different feeding types is adaptively related to use of the bill. Sexual dimorphism in head-shape and bite-force was detected, with females having longer bills than males for a given body size. Moreover, our results show strong differences in bill- and head-morphology between feeding types, with base-crushers having higher bite-forces and also relatively high bite-forces at the tip compared to probers and tip-biters. Finally, our finite-element models suggest that the shape of the bill in the tip-biters and base-crushers confers mechanical advantages by minimising stress in tip-loading and base-loading conditions, respectively, thus reducing probabilities of fracture. Our data support the contention that bill-shape is adaptive and evolves under selection for mechanical optimisation through natural selection on feeding mode.

Electrical machines and transformers have a core built out of laminations of ferromagnetic materials. A portion of the vibrations and noise of these devices is due to magnetic forces and magnetostriction arising from the magnetic core. Magnetic forces are well known, and analytical methods are extensively used to calculate them. Magnetostriction can be defined as the deformation of the ferromagnetic material in the presence of a magnetic field. Unlike magnetic forces, magnetostriction shows a rather complex behavior. It varies for every material, and it depends on the applied magnetic field and external pressure. Therefore, magnetostrictive behavior of every material needs to be determined experimentally by means of strain measurements. Strain gauge measurement techniques have been used before at the Electrical Energy Laboratory (EELAB), Ghent University, Ghent, Belgium. In this paper, a new measurement method using dual heterodyne laser interferometers is proposed to overcome the drawbacks of the old method. The proposed measurement setup and the working principles are explained. The possibility to apply both techniques on one and the same sample can also reveal some interesting results about the quality of both techniques.

To date, the use of liquid crystal grid projection for profilometric applications is gaining in popularity because of its flexibility. Liquid crystal projection devices allow easy adaption of the grid pitch (and thus sensitivity) in for instance Moiré topography, and in-plane translation of the grid position is also readily achieved. However, all methods either use Fourier transform profilometry or digital demodulation in the computer, with the advantage being the measurement speed. The major disadvantage is that the resolution is compromised. Only optical demodulation combined with phase-shifting methods does not yield any resolution. In this paper, we describe a technique which performs this optical demodulation as well as the grid projection with grids on liquid crystal light modulators. This entirely liquid crystal Moiré projection profilometer thus achieves higher resolution, flexibility and ease-of-use than the solely LCD grid projection setups. Theory and application examples are given in this paper, and a study is made of different parameters and algorithms influencing the resolution.

Direct measurements are presented of the area change and volume displacement of a human tympanic membrane under static pressures in the range of -1.6 KPa to +1.6 kPa. The area change is given separately for the pars tensa and the pars flaccida. For the pars tensa a strong asymmetry in area change under positive and negative pressure is observed. The volume displacement is also given separately for the pars tensa and the pars flaccida. The volume displacement of the entire TM agrees very well with volume displacement data in literature on tympanometry. It is shown further that a linear relationship between umbo displacement and volume displacement exists. The compliance of the tympanic membrane under static pressure load is compared to acoustic compliance measurements at low frequencies, and found to be a factor 2.5 higher than the compliance at 500 Hz.

Structured light projection techniques are an important and popular approach for whole-field surface topography. Within this branch, projection moire interferometry is our preferred optical metrology method. The use of liquid crystal display (LCD) projectors to produce structured light patterns has been proposed and used before in projection moire. It allows fast and easy adaptation of the grid pitch and thus measurement sensitivity. In this paper we will show how using a second liquid crystal panel makes the projection moire technique even more versatile and performant: The setup incorporates optical demodulation (OD) which in turn allows for accurate phase-shifting and the use of phase-shifting algorithms (PSAs). The Z-resolution is high and no filtering or interpolation is needed in X-Y by using the gray scale value variations through the phase-shifting and optical demodulation. Thus, we make optimal use of the camera pixel resolution and achieve an uncompromised measuring resolution. Furthermore, the setup is entirely digitally controlled, needs no physical interaction and avoids mechanically moving component. The low-cost setup, technique and theory will be covered in this talk. The resolution and other performance properties will be discussed and demonstrated. And to conclude, an application to achieve elasticity parameters of membranes will be shown. interferometry is our preferred optical metrology method. The use of liquid crystal display (LCD) projectors to produce structured light patterns has been proposed and used before in projection moire. It allows fast and easy adaptation of the grid pitch and thus measurement sensitivity. In this paper we will show how using a second liquid crystal panel makes the projection moire technique even more versatile and performant: The setup incorporates optical demodulation (OD) which in turn allows for accurate phase-shifting and the use of phase-shifting algorithms (PSAs). The Z-resolution is high and no filtering or interpolation is needed in X-Y by using the gray scale value variations through the phase-shifting and optical demodulation. Thus, we make optimal use of the camera pixel resolution and achieve an uncompromised measuring resolution. Furthermore, the setup is entirely digitally controlled, needs no physical interaction and avoids mechanically moving component. The low-cost setup, technique and theory will be covered in this talk. The resolution and other performance properties will be discussed and demonstrated. And to conclude, an application to achieve elasticity parameters of membranes will be shown.

Correct quantitative parameters to describe tympanic membrane elasticity are an important input for realistic modeling of middle ear mechanics. In the past, several attempts have been made to determine tympanic membrane elasticity from tensile experiments on cut-out strips. The strains and stresses in such experiments may be far out of the physiologically relevant range and the elasticity parameters are only partially determined. We developed a setup to determine tympanic membrane elasticity in situ, using a combination of point micro-indentation and Moire profilometry. The measuring method was tested on latex phantom models of the tympanic membrane, and our results show that the correct parameters can be determined. These parameters were calculated by finite element simulation of the indentation experiment and parameter optimization routines. When the apparatus was used for rabbit tympanic membranes, Moire profilometry showed that there is no measurable displacement of the manubrium during the small indentations. This result greatly simplifies boundary conditions, as we may regard both the annulus and the manubrium as fixed without having to rely on fixation interventions. The technique allows us to determine linear elastic material parameters of a tympanic membrane in situ. In this way our method takes into account the complex geometry of the membrane, and parameters are obtained in a physiologically relevant range of strain.

It is generally accepted that the middle ear acts mainly as a linear system for sound pressures up to 130 dB SPL in the auditory frequency range. However, at quasi-static pressure loads a strong nonlinear response has been demonstrated. Consequently, small nonlinear distortions may also be present in the middle ear response in the auditory frequency range. A new measurement method was developed to quickly determine vibration response, nonlinear distortions and noise level of acoustically driven biomechanical systems. Specially designed multisines are used for the excitation of the test system. The method is applied on a gerbil eardrum for sound pressures ranging from 90 to 120 dB SPL and for frequencies ranging from 125 Hz to 16 kHz. The experiments show that nonlinear distortions rise above noise level at a sound pressure of 96 dB SPL, and they grow as sound pressure increases. Post-mortem changes in the middle ear influence the nonlinear distortions rapidly until a stabilization occurs after approximately 3 h.

Computer modeling of middle ear mechanics is an important tool to investigate its complex behavior, but correct mechanical and elastic parameters are needed to obtain realistic simulations. A possible way to determine eardrum elasticity in situ is the use of point indentation measurements. The eardrum is, however, a small fragile membrane, so a non-contacting high-resolution technique is needed to measure the shape change caused by point indentation. We have developed a projection moire interferometer combined with an indentation actuator and a high-resolution force sensor. The apparatus applies deformations up to 1 mm with a resolution of 1 μ m , while the indentation force is measured with a resolution better than 1 mN. The moire setup delivers height data on 512 × 512 points through phase-shifting, with a height resolution of 15 μ m . Shape recordings are made on a rabbit eardrum at different indentation distances, and indentation force is recorded simultaneously.

A new optical-fluorescence microscopy technique, called HR-OPFOS, is discussed and situated among similar OPFOS-implementations. OPFOS stands for orthogonal-plane fluorescence optical sectioning and thus is categorized as a laser light sheet based fluorescence microscopy method. HR-OPFOS is used to make tomographic recordings of macroscopic biomedical specimens in high resolution. It delivers cross sections through the object under study with semi-histological detail, which can be used to create three-dimensional computer models for finite-element modeling or anatomical studies. The general innovation of this class of microscopy setup consists of the separation of the illumination and observation axes, but now in our setup combined with focal line scanning to improve sectioning resolution. HR-OPFOS is demonstrated on gerbil hearing organs and on mouse and bird brains. The necessary specimen preparation is discussed

One of the most important uses of Moire fringes is profilometry of 3-D surfaces. Grid lines are projected onto an object, and the deformed projection is imaged onto a second grid to obtain Moire fringes [1]. Grid noise is removed by translating both grids simultaneously in their own plane. To obtain the surface height information the fringes can be traced, but much more detailed information is obtained by applying a phase shifting technique. The necessary phase-shifts of the Moire fringes are obtained by changing the relative distance between the two grids. From at least three phase-shifted Moire fringe patterns, object surface height is then calculated on all pixel points of the camera which records the Moire fringe patterns. Classically, translation of the grids is performed mechanically. Recently we have introduced a method using two liquid crystal light modulators to perform high resolution phase-shifting Moire topography without any mechanically moving parts [2]. We will now show how this new method can be implemented using a low-cost consumer product LCD projector.

The effect of static pressures in the range of plus and minus 1.6 kPa on the shape of tympanic membrane is measured using a non-contacting optical technique on a fresh human temporal bone. Full field data of the deformation are presented as well as cross-sections along two major directions. Strong asymmetry between medial and lateral movements is demonstrated. The displacement of the umbo is compared to other work. The rotation angle of the manubrium in function of pressure is calculated and also compared to other work. It is demonstrated that the rotation angels can not account for the measured movement of the umbo, which leads to the conclusion that for static high pressure levels the classical hypothesis of rotation around a fixed axis has to be abandoned. The comparison with data of TM displacement under dynamic stimuli is discussed.

Conclusions. The model appears relevant for studies on sequelae after acute otitis media (AOM), and may be the seed of a new, chronic tympanic membrane perforation model in the gerbil. Objectives. To evaluate an experimental model for abortive otitis media and to assess the structural and functional changes of the tympanic membrane in the resolving phase. Materials and methods. The middle ears of 16 Mongolian gerbils were inoculated with type 6a Streptococcus pneumoniae. Half of the animals were treated with antibiotics on days 46, when otoscopy was performed as well. After 1, 2, 3 or 4 weeks the animals were sacrificed and their tympanic membranes were examined by otoscopy, dissection microscopy, light microscopy and moire´ interferometry. Results. On days 4 and 6 AOM was produced in approximately 80% of the animals and perforations prevailed in approximately 30% at the study end points. Clinical signs of AOM and oedema of the tympanic membrane had already started to reduce after 1 week, and often resolved within 2 weeks. The mechanical stiffness of the tympanic membrane remained relatively unharmed in the non-perforated ears. The antibiotic treatment seemed to reduce the duration of oedema but not the perforation rate.

The middle ear ossicles transmit sound from eardrum to inner ear under largely varying ambient pressure conditions. To protect the structures within the cochlea from excessive footplate incursions the configuration of the ossicles changes with pressure. Sequences of micro CT-scans were acquired from gerbil temporal bones under static ear canal pressures ranging from -450 to +450 daPa. These image stacks were used to track the 3D motion and deformations of the ossicles as a function of pressure using hyperelastic warping [1]. Using the scans for zero pressure, accurate finite-element reference models were generated for each of the ossicles. With the difference between these template images and the target image data recorded in a deformed configuration as a driving force, the warping algorithm displaced and deformed the finite-element models of the ossicles in order to align the deformed template with the target data. Position changes of the ossicles within the middle ear cavity and deformation of the ossicles and the tympanic membrane were all measured in a same preparation. For each static pressure load a finite-element ossicular chain model is obtained in the run and can be used for further analysis under acoustic stimulation.

Recently, a measurement set-up was presented to detect small nonlinear distortions in the vibration of acoustically driven mechanical systems. A speaker generates a specially designed multisine excitation signal that drives the vibration of a test object. The generated sound pressure is measured with a probe microphone in front of the test object, and an heterodyne vibrometer measures the corresponding vibration. Due to the high degree of linearity of the heterodyne technique, very small nonlinear distortions can be detected. In this paper the set-up is used to verify whether small nonlinear distortions are present in the vibration of the middle ear system, which is classically considered to be a completely linear system. In vitro measurements on the right ear of an adult male gerbil proved that nonlinear distortions are present in the vibration of the tympanic membrane. Similar results were seen in measurements on the left ear. The influence of post-mortem changes on the nonlinear behaviour of the middle ear was verified in a number of successive measurements. These indicated that the nonlinear behaviour of the middle ear decreases in time.

A projection moire profilometer is presented in which both projection and optical demodulation are realized with liquid crystal light modulators. The computer generated grids, realized on thin film transistor matrices, allow phase-stepping and discrete grid averaging without the need for any mechanically moving component. Spatial line pitch and phase steps can thus be readily adjusted to suit the measurement precision and object geometry. The device is able to perform topographic measurements with a height resolution of 15 microm on every pixel of the recording device.

A projection moire interferometer for topography is presented, which uses liquid crystal light modulators for both projection and demodulation grid. High resolution is obtained by optical demodulation, the 4-bucket algorithm and discrete grid averaging theory.

A technique for measuring in real-time continuous out-of-plane displacements of delicate objects is proposed, and demonstrated on the tympanic membrane of Mongolian Gerbil. The technique is based on the combination of two methods: the spatial phase shifting (SPS) and the modified temporal phase unwrapping (TPU). The combination allows to obtain, in several steps, the phase values of the points that undergo out-of-plane displacement as the object is deformed. The technique reduces the frame acquisition time of the standard TPU used in moiré interferometry by a factor of 4, which is important to diminish post-mortem artifacts during in-vitro experiments and to reduce motion artifacts in in-vivo tests. The proposed technique is robust against problems associated with the temporal phase-shifting method, such as nonlinear phase shift and noise. The advantages and disadvantages are discussed.

Recently we introduced a dual-beam heterodyne interferometer where combinations of half-silvered and fully reflecting mirrors were used to achieve beam doubling. We now propose a quadruple-beam system in which birefringent beam displacers generate the four parallel beams. We present the design and the performance characteristics of this apparatus.

This study examines whether a relation exists between rapid atmospheric pressure fluctuations, attributed to the far infrasound frequency range (APF), and a number of emergency transport events coded as circulatory system diseases (EEC). Over an entire year, the average integral amplitudes of APF in the range of periods from 3 s to 120 s over each hour (HA) were measured. Daily dynamics of HA averaged over the year revealed a wave shape with smooth increase from night to day followed by decrease from day to night. The total daily number of EEC within the city of Kiev, Ukraine, was related to the daily mean of HA (DHA) and to the ratio of HA averaged over the day time to HA averaged over the night time (Rdn), and was checked for confounding effects of classical meteorological variables through non-parametric regression algorithms. The number of EEC were significantly higher on days with high DHA (3.72–11.07 Pa, n = 87) compared to the low DHA (0.7–3.62 Pa, n = 260, p = 0.01), as well at days with low Rdn (0.21–1.64, n = 229) compared to the high Rdn (1.65–7.2, n = 118, p = 0.03). A difference between DHA and Rdn effects on the emergency events related to different categories of circulatory diseases points to a higher sensitivity of rheumatic and cerebro-vascular diseases to DHA, and ischaemic and hypertensive diseases to Rdn. Results suggest that APF could be considered as a meteorotropic factor capable of influencing circulatory system diseases.

Purpose: The normal function of the middle ear depends on the maintenance of a pressure close to ambient pressure. However, deviation in middle ear pressure (MEP) is a common finding in otitis media and related sequelae, and hence, it is considered a major pathogenetic factor. Up till now, available data were either obtained from indirect measurements, resulting in limited accuracy, or from short term acute experiments, or from longer term measurements in ears with perforated eardrums. The purpose of the present study was to introduce a new improved method for direct accurate monitoring of MEP in ambulant humans with intact eardrums. Materials and Methods: A new method is presented, where a catheter was inserted into the mastoid through a small hole drilled into its antero-lateral tip. Subjects included were patients admitted for parotidectomy, where this region is routinely exposed. The catheter was connected to a high accuracy pressure transducer (±1 Pa), and data were stored in a portable unit at a sampling rate of 10 Hz for up to 48 hours. Hence, MEP could be continuously monitored also after discharge from hospital for investigating pressure changes during daily life activities. The catheter was removed after 48 hours

In recent papers we have shown that the mode of vibration of the ossicular chain in cat and human temporal bones is more complex than a simple rotation about a fixed axis and that it also changes with frequency. For the stapes e.g. it was shown that rotations of the footplate about its long and short axis are present besides the predominant piston-like velocity component. As the footplate motion gives rise to the pressure wave set up in the cochlea, we investigated whether the non-piston components contribute to the pressure produced in the gerbil cochlea: 3-D vibration velocity of the stapes along with the scala vestibuli pressure were measured in the same animals. We found no correlation between non-piston components and scala vestibuli pressure.

Changes of gas quantity in a system can be measured either by measuring pressure changes or by measuring volume changes. As sensitive pressure sensors are readily available, pressure change is the commonly used technique. In many physiologic systems, however, buildup of pressure influences the gas exchange mechanisms, thus changing the gas quantity change rate. If one wants to study the gas flow in or out of a biological gas pocket, measurements need to be done at constant pressure. In this article we present a highly sensitive sensor for quantitative measurements of gas volume change at constant pressure. The sensor is based on optical detection of the movement of a droplet of fluid enclosed in a capillary. The device is easy to use and delivers gas volume data at a rate of more than 15 measurements/s and a resolution better than 0.06 microl. At the onset of a gas quantity change the sensor shows a small pressure artifact of less than 15 Pa, and at constant change rates the pressure artifact is smaller than 10 Pa or 0.01% of ambient pressure.

Objective: The incidence of otitis media in children between the age of 2 and 6 years is well documented. Repeated attacks may cause acute and chronic perforations. The surgical treatment for repairing chronic perforation is quite uncomfortable for the patients of this age group because of the invasiveness of this treatment. The aim of this study was to determine the long-term influence of embryonic stem cells on acute perforations and the effect of gelatin as a vehicle for applied stem cells. The possibility of teratogenic effects of the stem cells was also observed. Methods: Bilateral laser myringotomy was Performed in 17 adult Sprague-Dawley rats, divided into two groups. Gelatin, a substance suitable as vehicle for bioactive material was used bilaterally around the perforation in group A, to serve as a scaffold for repairing tissue. The stem cells were used in the right tympanic membrane perforation leaving the left tympanic membrane as a control. The animals in group B received the same treatment except for the use of gelatin and in addition received an immuno-suppressive agent. After half a year of observation the mechanical stiffness of the tympanic membrane was measured by moire interferometry for group B and the morphological study was performed by light microscopy for both groups A and B and electron microscopy for group A. Results: Stem cell treated ears did not show any enhanced heating of the perforation although a marked thickening of the lamina propria was observed compared with control group. After half a year the strength and the stiffness of the tympanic membrane was almost the same for both treated and untreated ears. No evidence of teratoma was found after half a year. Conclusion: This study suggests that the stem cells stimulate the proliferation of connective tissue and fibers in the lamina propria, possibly mediated by secreted substances, although the stiffness properties do not seem to be altered. The use of gelatin does not seem to enhance the heating process of the tympanic membrane perforation. (C) 2007 Published by Elsevier Ireland Ltd.

In most experiments, access for direct measurement of stapes motion in line with the piston axis is not available and piston motion is estimated from single component interferometric measurements done under observation directions that make angles up to 60 degrees with the piston axis. We measured the vibration velocity of the stapes in human and gerbil from different observation angles and calculated the complete set of 3-D motion components. We expressed the components in an intrinsic reference system and could foretell the motion component to be recorded with a single axis interferometer at an angle with the piston axis. A cosine factor provides a good correction for the axis offset only for low frequencies (f

It was shown that the mode of vibration of the stapes has a predominant piston component but rotations producing tilt of the footplate are also present. Tilt and piston components vary with frequency. Separately it was shown that the pressure gain between ear canal and scala vestibuli was a remarkably flat and smooth function of frequency. Is tilt functional contributing to the pressure in the scala vestibuli and helping in smoothing the pressure gain? In experiments on gerbil the pressure in the scala vestibuli directly behind the footplate was measured while recording simultaneously the pressure produced by the sound source in the ear canal. Successively the three-dimensional motion of the stapes was measured in the same animal. Combining the vibration measurements with an anatomical shape measurement from a micro-CT (CT: computed tomography) scan the piston-like motion and the tilt of the footplate was calculated and correlated to the corresponding scala vestibuli pressure curves. No evidence was found for the hypothesis that dips in the piston velocity are filled by peaks in tilt in a systematic way to produce a smooth middle ear pressure gain function. The present data allowed calculations of the individual cochlear input impedances.

We describe a dual-channel laser velocimeter based on a single laser source and a single set of carrier wave generation optics. The apparatus is intended for simultaneous vibration measurements on several points of instable objects, such as biological specimens or micro electronic mechanical systems, so that instantaneous phase relationships and amplitude ratios can be determined. Our instrument presently allows measurements on two points of interest which can be arbitrarily chosen. The optical design allows expansion to at least four independent channels. At a maximal velocity amplitude of 52 mm s−1, the velocity resolution and the detection limit equal 2.6 μm s−1 Hz−1/2. Even with object points less than 0.4 mm apart, channel cross-talk is less than −78 dB at all frequencies.

The Oilbird and many Swiftlet species are unique among birds for their ability to echolocate. Echolocaters may benefit from improved hearing sensitivity. Therefore, morphological adaptations to echolocation might be present in echolocating birds’ middle ears. We studied the functional morphology of the tympano–ossicular chain of seven specimens of four echolocating Swiftlet species and one specimen each of five non-echolocating species. Three dimensional (3D) reconstructions were made from micro-Computer-Tomographic (μCT) scans. The reconstructions were used in functional morphological analyses and model calculations. A two dimensional (2D) rigid rod model with fixed rotational axes was developed to study footplate output-amplitudes and to describe how changes in the arrangement of the tympano–ossicular chain affect its function. A 3D finite element model was used to predict ossicular-chain movement and to investigate the justification of the 2D approach. No morphological adaptations towards echolocation were found in the middle-ear lever system or in the mass impedance of the middle ear. A wide range of middle-ear configurations result in maximum output-amplitudes and all investigated species are congruent with these predicted best configurations. Echolocation is unlikely to depend on adaptations in the middle ear tympano–ossicular chain.

Moiré topography is a well-established optical technique to measure the shape of three-dimensional surfaces, based on the geometric interference between an optical grid and its image deformed by an object surface. The technique produces fringes that represent contours of equal height, and from the recordings of several phase-shifted topograms surface height coordinates can be calculated. To perform these calculations, it is assumed that object height variation is small in comparison with the measurement setup dimensions, and this approximation leads to systematic errors in measurement accuracy. We present the mathematical description of the fringe formation process in projection moiré topography, and on the basis of these equations we establish the relation between setup geometry and upper limits of the systematic measurement errors. We derive the equations that determine design specifications needed to reduce the effects of approximations to be below the measurement resolution of the setup. It is shown that setup geometry should be adapted to the gray-scale measurement resolution of the imaging system. We show that, using an iterative correction from one fringe order to the next, measurement accuracy can be maintained over the entire object depth.

Recently, a new method was proposed to measure nonlinear distortions in weak nonlinear systems using specially designed broadband excitation signals (odd random phase multisines). During one single experiment, the output response level, the noise level and the level of the nonlinear distortions are simultaneously measured. We implement this method in an opto-acoustic set-up which allows us to measure vibrations with high accuracy. To demonstrate the method, we present results obtained on the membrane of an earphone speaker and a latex membrane. On the earphone good agreement is found between measurements of the produced sound field and the actual membrane vibration using heterodyne interferometry. The results show that heterodyne vibrometry can be used to detect nonlinear distortions which are up to 80 dB below the output level in an acoustically driven system.

Designing very robust structures in an efficient way is a reoccurring challenge in engineering. For male stag beetle weaponry, the solution to this problem was evolved by natural and sexual selection. Stag beetle armature is adapted to perform under extreme circumstances: male stag beetles fight pugnacious battles over females, by using their extremely large jaws as ferocious weapons. During violent encounters, these jaws have to withstand forces with a wide range of unpredictable directions at several application points. We constructed 1020 finite element models with different input forces to investigate how the male jaws are structurally adapted to avoid failure. The cross-sectional shape of the jaw is adapted to provide robustness against the reaction forces of biting. Nevertheless, the jaw's shape cannot prevent the fact that bite forces induce relatively high material stresses compared to other force directions. Also, males do not confine themselves in combats to bite with the most robust jaw regions. Both observations emphasize the usefulness of bite force modulation to avoid jaw failure. This is likely effectuated by a sensory network in the jaw exoskeleton, as sensor densities are nicely correlated to the maximal material stress caused by 510 different loading directions. Probably, stag beetles use this sensory information to adjust their fighting strategy as well. Finally, male jaws also need to resist the forceful bites inflicted by opponents. Even though this loading applies at other locations along the jaw, and bends the jaw in the opposite direction, our models show that the jaws are equally robust against these external forces as they are against the forces caused by their own biting.

A real-time microscopic profilometry system based on digital fringe projection and parallel programming has been developed and experimentally tested. Structured light patterns are projected onto an object through one pathway of a stereoscopic operation microscope. The patterns are deformed by the shape of the object and are then recorded with a high-speed CCD camera placed in the other pathway of the microscope. As the optical pathways of both arms are separated and reach the same object point at a relative angle, the recorded patterns allow the full-field object height variations to be calculated and the three-dimensional shape to be reconstructed by employing standard triangulation techniques. Applying proper hardware triggering, the projector-camera system is synchronized to capture up to 120 unique deformed line patterns per second. Using standard four-step phase-shifting profilometry techniques and applying graphics processing unit programming for fast phase wrapping, scaling, and visualization, we demonstrate the capability of the proposed system to generate 30 microscopic height maps per second. This allows the qualitative depth perception of the stereomicroscope operator to be enhanced by live quantitative height measurements with depth resolutions in the micrometer range. (C) 2015 Optical Society of America

Due to changes in ambient pressure and to the gas-exchange processes in the middle ear (ME) cavity, the ear is subject to ultra-low-frequency pressure variations, which are many orders of magnitude larger than the loudest acoustic pressures. Little quantitative data exist on how ME mechanics deals with these large quasi-static pressure changes and because of this lack of data, only few efforts could be made to incorporate quasi-static behavior into computer models. When designing and modeling ossicle prostheses and implantable ME hearing aids, the effects of large ossicle movements caused by quasi-static pressures should be taken into account. We investigated the response of the ME to slowly varying pressures by measuring the displacement of the umbo and the stapes in rabbit with a heterodyne interferometer with position decoder. Displacement versus pressure curves were obtained at linear pressure change rates between 200 Pa/s and 1.5 kPa/s, with amplitude +/-2.5 kPa. The change in stapes position associated with a pressure change is independent of pressure change rate (34 microm peak-to-peak at +/-2.5 kPa). The stapes displacement versus pressure curves are highly nonlinear and level off for pressures beyond +/-1 kPa. Stapes motion shows no measurable hysteresis at 1.5 kPa/s, which demonstrates that the annular ligament has little viscoelasticity. Hysteresis increases strongly at the lowest pressure change rates. The stapes moves in phase with the umbo and with pressure, but the sense of rotation of the hysteresis loop of stapes is phase inversed. Stapes motion is not a simple lever ratio mimic of umbo motion, but is the consequence of complex changes in ossicle joints and ossicle position. The change in umbo position produced by a +/-2.5 kPa pressure change decreases with increasing rate from 165 microm at 200 Pa/s to 118 microm at 1.5 kPa/s. Umbo motion already shows significant hysteresis at 1.5 kPa/s, but hysteresis increases further as pressure change rate decreases. We conclude that in the quasi-static regime, ossicle movement is not only governed by viscoelasticity, but that other effects become dominant as pressure change rate decreases below 1 kPa/s. The increasing hysteresis can be caused by increasing friction as speed of movement decreases, and incorporating speed-dependent friction coefficients will be essential to generate realistic models of ossicle movements at slow pressure change rates.

Current finite-element (FE) models of the eardrum are limited to low pressures because of the assumption of linearity. Our objective is to investigate the effects of geometric nonlinearity in FE models of the cat eardrum with an approximately immobile malleus for pressures up to +/-2.2 kPa, which are within the range of pressures used in clinical tympanometry. Displacements computed with nonlinear models increased less than in proportion to applied pressure, similar to what is seen in measured data. In both simulations and experiments, there is a shift inferiorly in the location of maximum displacement in response to increasingly negative middle-ear pressures. Displacement patterns computed for small pressures and for large positive pressures differed from measured patterns in the position of the maximum pars-tensa displacement. Increasing the thickness of the postero-superior pars tensa in the models shifted the location of the computed maximum toward the measured location. The largest computed pars-tensa strains were mostly less than 2%, implying that a linearized material model is a reasonable approximation. Geometric nonlinearity must be considered when simulating eardrum response to high pressures because purely linear models cannot take into account the effects of changing geometry. At higher pressures, material nonlinearity may become more important.

This study was designed to clarify whether the pars flaccida (PF) as a flexible part of the tympanic membrane is capable of reacting to pressure oscillations (PO) with amplitudes and frequencies typical for natural atmospheric pressure fluctuations in the far infrasound frequency range (APF). If so, the PF mechanical reactions to APF might be involved in the overall physiologic regulation processes, which make organisms susceptible to APF. The displacements of the PF in response to PO were measured in vitro in ears of gerbils and rabbits by means of laser Doppler vibrometry. The index of the PF reactivity (R(a)) was determined as the ratio of the amplitude of the PF oscillations (PFO) to the amplitude of the PO. All kinds of PO applied caused PFO. The amplitude of the PFO increased when the amplitude of the PO was increased. In gerbils, a decrease in R(a) with the increase in amplitude of the PO was observed. In the range of PO lowest amplitudes (4-20 Pa) R(a) proved to be 1.4 times higher than in the range of highest amplitudes (90-105 Pa). Considering that the natural APF are usually within the range of +/-20 Pa, this fact points to an important contribution of the PF to the pressure dynamics in the middle ear (ME) of gerbils. In rabbit ears, R(a) was lower and recovery from plastic deformation was slower than in gerbils. Our findings are in line with the suggestion that the PF might play an important role in respect of adaptation to natural APF.

We have adapted a Mach-Zender type laser velocimeter for making simultaneous measurements at several, arbitrarily chosen points. The optical design is based on a single laser source and two acousto-optic modulators, which generate a common heterodyne carrier frequency in all measurement channels. By using two modulators, one to increase the frequency of the reference beam with 80 MHz, and a second one which decreases the frequency with a bit more than 80 MHz, we can adjust the heterodyne beat signal to any frequency of choice, thus adapting it to the input of commercially available FM demodulation chips or avoiding noisy parts of the laser noise spectrum. The apparatus is intended for simultaneous vibration measurements at several points of instable objects, such as biological specimens or MEMS, so that instantaneous phase relationships and amplitude ratios can be determined. So far, instrument performance has been tested with measurements on two points of interest. In a multipoint system, especially when it uses a single laser source and a common heterodyne frequency, channel cross talk is a major point of concern. The optical design ensures very good channel separation and allows expansion to at least four channels. We present channel separation measurements obtained with one channel focused on a vibrating membrane or a vibrating plate and the other focused on an adjacent solid object. Even with these object points less than 0.4 mm apart, channel separation was found to be better than 78 dB at all frequencies. The velocity calibration of the system is determined by the laser wavelength and the sensitivity of the FM detection circuitry only. With a maximal velocity amplitude of 52 mm/s, the velocity resolution and the detection limit of our system were determined to be 2.6 square root(bandwidth) μm.s-1Hz-1/2 in both channels.

Transmucosal CO2 exchange in the middle ear (ME) of the New Zealand White rabbit (Oryctolagus cuniculus) was studied using an accurate novel detecting and recording system for measuring gas volume changes at constant pressure, based on a principle that was previously used by Kania et al. (Acta Otolaryngol 124:408–410, 2004). After the ME cavity was washed with ambient air, the initial diffusion rate of CO2 ( % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!% MathType!MTEF!2!1!+-% feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX% garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz% aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq% Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq% Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaada% WfGaqaaiaadAfaaSqabeaacqGHIaYTaaGcdaWgaaWcbaGaaeyAaaqa% baqcaaMaae4qaiaab+eakmaaBaaajeaybaGaaGOmaaqabaaaaa!3EAD! $${\mathop V\limits^ \bullet }_{{\text{i}}} {\text{CO}}_{2} $$ ) from the blood perfusing the ME mucosa was calculated from gas volume change measurements. In nine cases, the % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!% MathType!MTEF!2!1!+-% feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX% garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz% aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq% Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq% Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaada% WfGaqaaiaadAfaaSqabeaacqGHIaYTaaGcdaWgaaWcbaGaaeyAaaqa% baqcaaMaae4qaiaab+eakmaaBaaajeaybaGaaGOmaaqabaaaaa!3EAD! $${\mathop V\limits^ \bullet }_{{\text{i}}} {\text{CO}}_{2} $$ calculated after normalization due to shifts in baseline was 314 ± 112 μL·h−1 (mean ± SD). In two cases where normalization was not needed, % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!% MathType!MTEF!2!1!+-% feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX% garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz% aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq% Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq% Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaada% WfGaqaaiaadAfaaSqabeaacqGHIaYTaaGcdaWgaaWcbaGaaeyAaaqa% baqcaaMaae4qaiaab+eakmaaBaaajeaybaGaaGOmaaqabaaaaa!3EAD! $${\mathop V\limits^ \bullet }_{{\text{i}}} {\text{CO}}_{2} $$ was 409 μL·h−1 (276 and 543 μL·h−1). Normalization of % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!% MathType!MTEF!2!1!+-% feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX% garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz% aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq% Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq% Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaada% WfGaqaaiaadAfaaSqabeaacqGHIaYTaaGcdaWgaaWcbaGaaeyAaaqa% baqcaaMaae4qaiaab+eakmaaBaaajeaybaGaaGOmaaqabaaaaa!3EAD! $${\mathop V\limits^ \bullet }_{{\text{i}}} {\text{CO}}_{2} $$ data was also made in five additional cases where secretion of fluids from the lining of the ear canal was observed. In these cases % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!% MathType!MTEF!2!1!+-% feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX% garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz% aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq% Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq% Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaada% WfGaqaaiaadAfaaSqabeaacqGHIaYTaaGcdaWgaaWcbaGaaeyAaaqa% baqcaaMaae4qaiaab+eakmaaBaaajeaybaGaaGOmaaqabaaaaa!3EAD! $${\mathop V\limits^ \bullet }_{{\text{i}}} {\text{CO}}_{2} $$ was 245 ± 142 μL·h−1. No differences were found between results obtained in the three groups. Thus, an overall mean value of % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!% MathType!MTEF!2!1!+-% feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX% garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz% aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq% Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq% Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaada% WfGaqaaiaadAfaaSqabeaacqGHIaYTaaGcdaWgaaWcbaGaaeyAaaqa% baqcaaMaae4qaiaab+eakmaaBaaajeaybaGaaGOmaaqabaaaaa!3EAD! $${\mathop V\limits^ \bullet }_{{\text{i}}} {\text{CO}}_{2} $$ of 305 ± 131 μL·h−1 (n = 16) was calculated. An effective coefficient of conductance of CO2 (G 2) between the mucosal circulation and the ME gas cavity of the New Zealand White rabbit was estimated to be ≈0.05 μL (h·Pa)−1 and compared to the G 2 estimated for humans in a different study.

Refractive index of tissue is an essential parameter in many bio-optical experiments, yet little data can be found in literature. Several methods have been proposed to measure refractive index in tissue samples, but all have specific limitations, such as low accuracy, the need for large amounts of tissue, or the complexity of the measurement setup. We propose a new method using a standard confocal microscope and requiring only small tissue samples. A thin slice of tissue is put next to a layer of immersion fluid of exactly the same thickness. The actual thickness of the fluid layer is directly measured with the microscope, as there is no refractive index mismatch. A difference between index of refraction of the tissue and of the immersion medium causes an axial scaling factor. The optical thickness of the specimen is thus measured with the microscope, and as its actual thickness equals the known thickness of the fluid layer, the axial scaling factor is readily determined. From this factor, we calculate the refractive index of the tissue. We use a diffraction model to take the point spread function (PSF) of the microscope into account, so we can determine the index of refraction to a very high accuracy. We demonstrate the method on bovine muscle tissue and find a value of n = 1.382 +/- 0.004, at 592 nm. (C) 2005 Society of Photo-Optical Instrumentation Engineers.

The aim of this study was to measure the spatial thickness distribution of the cat tympanic membrane (TM), a very thin, virtually transparent and delicate biological membrane. Axial fluorescence images taken perpendicular through isolated TM were recorded for five different cats using confocal laser scanning microscopy. Thickness was measured on the cross-section of the membranes in the axial images. A correction for focal shift due to refractive-index mismatch was applied. Similar thickness distributions were obtained in all measured samples (n = 9). The pars tensa had a rather constant thickness in the central region between the annulus and manubrium. The thickness increased steeply toward the peripheral rim. Thickness was smallest in the inferior region, with values ranging between 5.5 and 9 microm in the central part and up to 50 microm near the annulus. More superiorly, thickness was slightly higher, up to 20 microm, between the annulus and manubrium. The anterior part was thicker than the posterior side. These findings are strongly different from a current value in the literature. Our data allow a more precise representation of the eardrum in mathematical models, which are a prerequisite for a better understanding of middle-ear mechanics. The optical sectioning technique of the confocal microscope did not result in any preparation artifacts and was therefore also used to quantify shrinkage due to preparation of histological sections of TMs.

Thickness data for the gerbil tympanic membrane, an extremely thin biological membrane, are presented. Thickness measurements were performed on fresh material using fluorescence images taken perpendicular through the membrane with a commercial confocal microscope. Thickness varies strongly across the membrane. Similar thickness distributions in all samples (pars tensa n = 11; pars flaccida n = 3) were observed. The pars tensa has a rather constant thickness of about 7 microm in the central region curving as a horse shoe upwards around the manubrium. In the most superior parts of the pars tensa thickness becomes gradually twice as large. Thickness increases also steeply from the central region towards the edges (about 35 microm near the annulus and 20 microm near the manubrium). A pronounced, local thickening of about 30 microm is present close to the edge and extends as a ring along the entire annular periphery of the pars tensa. Overall, the pars flaccida is thicker than the pars tensa and has a rugged surface. Its central region has a mean thickness of about 24 microm with a mean variation of about 4 microm. The average thickness in the inferior region is slightly larger than in the superior region. The pars flaccida thickens steeply, up to about 80 microm, near the edges.

In unstable objects, such as biological specimens, vibrational patterns can change quickly with time. To determine phase relationships between several vibrating points in such an object, it is therefore necessary to measure those points simultaneously. We describe a dual channel heterodyne interferometer capable to acquire vibrational data at two arbitrary spatial points simultaneouly over the entire acoustic frequency range. The design allows extension to four or even eight independent channels. Channel cross-talk is measured to be about -30 dB, below the S/N ratio within the signal channel. Velocity resolution is estimated to be 10 mu m/s, corresponding to an amplitude resolution of 1.5 nm at 1 kHz.

HYPOTHESIS The mechanical and structural properties of the tympanic membrane change after a perforation has healed. BACKGROUND In previous studies, efforts have been made to enhance the healing process of tympanic membrane perforations. The strength of the healed perforation has been tested with moire interferometry in gerbils, but in no other species. METHODS A laser myringotomy was made on 10 Sprague-Dawley rats and 10 CBA mice, and assessments were made after 2 or 4 weeks with moire interferometry and light and electron microscopy. RESULTS The mean peak displacement at pressure loads of +350 daPa and of -350 daPa did not differ significantly in the healed perforations as compared with the untouched tympanic membranes. Morphologic assays showed fivefold increased thickness at the site of the perforation due to invaded fibroblasts and extracellular matrix. CONCLUSION Moire interferometry was successfully performed in the rat ears, whereas in mouse ears the method was not easily applicable due to technical difficulties. The stress-strain curve of the rat tympanic membrane displays an S-shape. The strength of the spontaneously healed tympanic membrane after myringotomy was not significantly impaired. The site of the perforation became significantly thickened at 2 and 4 weeks post-myringotomy. This information is of clinical importance, because recently closed perforations will be challenged by pressure gradient in everyday life.

A phase-shift shadow moiré interferometer was used to measure the shape of the cat eardrum with a normal mobile malleus and with an immobile malleus as it was cyclically loaded with static middle-ear pressures up to +/-2.2 kPa. The shape was monitored throughout the loading and unloading phases, and three complete cycles were observed. The mobile-manubrium measurements were made in five ears. In three ears, the malleus was then immobilized with a drop of glue placed on the head of the malleus. Eardrum displacements were calculated by subtracting shape images pixel by pixel. The measurements are presented in the form of gray-level full-field shape and displacement images, of displacement profiles, and of pressure-displacement curves for selected points. Displacement patterns with a mobile malleus show that pars-tensa displacements are larger than manubrial displacements, with the maximum pars-tensa displacement occurring in the posterior region in all cats except one. Displacements vary from cycle to cycle and display hysteresis. For both the mobile-malleus and immobile-malleus cases, the eardrum response is nonlinear. The response is asymmetric, with lateral displacements being larger than medial displacements. With a mobile malleus, manubrial displacements exhibit more pronounced asymmetry than do pars-tensa displacements.