2D Modeling of the Human Ear Using the Equivalent Mechanical Impedance

Several mass–spring–damper models have been developed to study the response of the human body parts. In such models, the lumped elements represent the mass of different body parts, and stiffness and damping properties of various tissues. The aim of this research is to develop a 2D axisymmetric model to simulate the motion of the human tympanic membrane. In this contribution we develop our model using a Comsol Multiphysics software to construct a 2D axisymmetric objects, the acoustic structure interaction between the ear canal (field of propagation of the acoustic wave) and the structure of ear (skin, cartilage, bone, tympanic membrane) was solved using finite elements analysis (FEA). A number of studies have investigated the motion of the human tympanic membrane attached to the ossicular chain and the middle ear cavity. While, in our model the tympanic annular is assumed to be fixed and the loading of what comes behind the tympanic membrane as the ossicular chain, middle ear cavity and cochlea were replaced by the equivalent mechanical impedance of a spring mass damper system. The obtained results demonstrate that the maximum displacements of the umbo are obtained at the frequency range of [0.9 - 2.6] kHz, the sound pressure gain had the shape of peak with a maximum at [2 – 3] kHz frequency range. The umbo displacement depends on the damping coefficient d, and the sound pressure at the tympanic membrane was enhanced compared to that at the ear canal entrance.

Mimicking the Human Tympanic Membrane: the Significance of Geometry

The human tympanic membrane (TM) captures sound waves reaching the outer ear from the environment and transforms them into mechanical motion. The successful transmission of these acoustic vibrations in varying frequency ranges is attributed to the structural architecture of the TM. However, a limited knowledge is available on the contribution of its discrete anatomical features, which is important to fabricate functional biomimetic TM replacements. This work synergizes theoretical and experimental approaches toward understanding the significance of geometry in tissue engineered TM scaffolds. Three test designs along with a plain control were chosen to decouple some of the dominant structural attributes, such as, the radial and circumferential alignment of the collagen fibrils. In silico models suggested a geometrical dependency of their mechanical and acoustical responses, where the presence of radially aligned fibers was observed to have a more prominent effect compared to their circumferential counterparts. Following which, a hybrid fabrication strategy combining electrospinning and additive manufacturing was optimized to manufacture hierarchical scaffolds within the dimensions of the native TM. The experimental characterizations conducted using macro-indentation and laser Doppler vibrometry were in line with the computational models. Finally, biological studies performed with human dermal fibroblasts and human mesenchymal stromal cells, revealed a favorable influence of scaffold hierarchy on cellular alignment and subsequent collagen deposition.Abstract FigureGraphical abstract.Schematic diagram illustrating the overall flowchart of the work. 3D: three-dimensional; ES: electrospinning; FDM: fused deposition modeling; TM: tympanic membrane.

Application of Multispectral Imaging in the Human Tympanic Membrane

Multispectral imaging has recently shown good performance in determining information about physiology, morphology, and composition of tissue. In the endoscopy field, many researches have shown the ability to apply multispectral or narrow-band images in surveying vascular structure based on the interaction of light wavelength with tissue composition. However, there has been no mention to assess the contrast between other components in the middle ear such as the tympanic membrane, malleus, and the surrounding area. Using CT, OCT, or ODT can clearly describe the tympanic membrane structure; nevertheless, these approaches are expensive, more complex, and time-consuming and are not suitable for most common middle ear diagnoses. Here, we show the potential of using the multispectral imaging technique to enhance the contrast of the tympanic membrane compared to the surrounding tissue. The optical absorption and scattering of biological tissues constituents are not the same at different wavelengths. In this pilot study, multiwavelength images of the tympanic membrane were captured by using the otoscope with LED light source at three distinct spectral regions: 450 nm, 530 nm, and 630 nm. Subsequently, analyses of the intensity images as well as the histogram of these images point out that the 630 nm illumination image features an evident contrast in the intensity of the tympanic membrane and malleus compared to the surrounding area. Analysis of such images could facilitate the boundary determination and segmentation of the tympanic membrane (TM) with high precision.

Analytical Study of Nonlinear Vibrations of the Tympanic Membrane by Homotopy Perturbation Method

Nonlinear vibration problems are generally of great importance in physics, mechanical structures, and other engineering research. This type of equation is very difficult and time-consuming. Researchers, therefore, focus on analytical and numerical methods; In this paper, using the new Newton-Harmonic Balance analytical method, which includes a combination of Newton methods and the harmonic balance method, the common Homotopy Perturbation method is used to solve the nonlinear equation of human tympanic membrane vibration and are compared and validated.