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Headphones and earphones have many extremely small holes or narrow slits; they use sound-absorbing or porous material (i.e., dampers) to suppress vibratory system resonance. The air viscosity in these acoustic paths greatly affects the acoustic properties. Simulation analyses such as the finite element method (FEM) therefore require knowledge of the material properties of sound-absorbing or por...

A method to compute the acoustic characteristics of a simplified three-dimensional vocal-tract model with asymmetric wall impedances is presented. The acoustic field is represented in terms of both plane waves and higher-order modes in tubes. This model is constructed using a connected structure of rectangular acoustic tubes, and can parametrically represent acoustic characteristics in higher f...

A preliminary evaluation of several nondestructive testing methods for flaw detection in hightemperature structural ceramic components is being carried out. The ceramics components being investigated include silicon carbide heat-exchanger tubes and silicon nitride rotors. The nondestructive evaluation techniques under consideration include dye-enhanced radiography, holographic interferometry, i...

We combine numerical simulations and experiments to design a new class of reconfigurable waveguides based on three-dimensional origami-inspired metamaterials. Our strategy builds on the fact that the rigid plates and hinges forming these structures define networks of tubes that can be easily reconfigured. As such, they provide an ideal platform to actively control and redirect the propagation o...

A model for calculating the acoustic characteristics of 3-D vocal tract con guration is presented. A mode-matching technique and an impedance transformation are used to calculate the higher-order modes in this model where both propagative and evanescent higher-order modes are considered. A cascaded structure of rectangular acoustic tubes is introduced as an approximation of the real vocal tract...

Acoustic waves in a rigid axisymmetric tube with a variable cross-section are considered. The governing Helmholtz equation is solved using Neumann series (expansions in Bessel functions of various orders) with a stretched radial coordinate, leading to a hierarchy of one-dimensional ordinary differential equations in the longitudinal direction. The lowest approximation for axisymmetric motion in...

A model for calculating the acoustic characteristics of three-dimensional vocal tract con guration is presented. A cascaded structure of rectangular acoustic tubes, connected asymmetrically with respect to their axes, is introduced as an approximation of the real vocal tract geometry. Both propagative and evanescent higher-order modes are considered in these tubes. The number of higherorder mod...