background: sound is one of the most important factors threatening workers’ health. the most efficient and practical method for controlling noise pollution is the use of sound-absorbing materials. impedance tube with two microphones is used to determine the sound absorption coefficients and should be tested periodically for accuracy and efficiency. the purpose of present study was assessing the...

A method is developed for measuring acoustic impedance. The method employs a one-dimensional tube or duct with excitation at one end and an unknown acoustic impedance at the termination end. Microphones placed in the tube are then employed to measure the frequency response of the system from which acoustic impedance of the end is calculated. This method uses fixed instrumentation and takes adva...

Background: Normal Eustachian tube function is one of the important factor required for successful tympanoplasty outcome. A clinically useful test for assessment of Eustachian tube function is still lacking. Aims And Objectives: To evaluate Eustachian tube function by impedance audiometry and compare the outcome of surgery with respect to graft take up in normal and abnormal Eustachian tube fun...

The primary objective is to obtain experimental measurements of the plane wave reflection coefficients from laboratory and in situ sediments using impedance tube [1] and acoustic resonator tube [2, 3] methods, in the frequency range of approximately 300 Hz to tens of kHz. This approach will also yield measurements of the acoustic impedance, sediment sound speed, attenuation, and complex density...

In accelerators with very short bunches, such as is envisioned in the undulator region of the Linac Coherent Light Source (LCLS)[1], the wakefield due to the roughness of the beam-tube walls can have important implications on the required smoothness and minimum radius allowed for the beam tube. Of two theories of roughness impedance, one yields an almost purely inductive impedance[2], the other...

We present a stochastic formulation of the inverse problem of determination of the inner radius and electromagnetic properties of metal tubes from the measured coil impedance. The inversion procedure is based on the Monte Carlo Markov chain method and the analytical impedance model developed and validated in our previous work. The impedance measurement uncertainty is included as the prior proba...

In an oscillatory flow, the resistance to flow, more appropriately defined as the impedance to flow, is a function of oscillating frequency, which refers to the harmonic composition of the driving pressure wave. Flow in an elastic tube may be resisted in numerous ways such as the fluid viscosity, fluid inertia and tube elasticity. The concept of impedance arises in the dynamics of the Resistanc...

Impedance pump is a simple valveless pumping mechanism, where an elastic tube is joined to a more rigid one; a periodic asymmetrical pinching on the elastic tube will produce a unidirectional flow. This pumping concept offers a low energy, low noise alternative at both micro and macro scales. This paper describes an experimental investigation of the performance of a two-stage, open loop impedan...

Measurement of respiratory impedance (Zrs) in intubated patients requires corrections for flow-dependent resistance and air compression inside the endotracheal tube (ET). The purpose of this study was to test a new correction technique for these effects. We therefore studied 110 patients in two conditions: breathing normally (C1), or breathing through an ET placed at the mouth (C2). In C1, we m...