Impedance tube measurement of propagation constant and characteristic impedance of porous acoustical material

1973 ◽  
Vol 54 (5) ◽  
pp. 1138-1142 ◽  
Author(s):  
Simone L. Yaniv
Keyword(s):  
Propagation Constant ◽  
Characteristic Impedance ◽  
Impedance Tube

Estimation and experimental test of the sound-absorption coefficient of a pin-holder structure (Case of sound waves incidence upon the side surfaces of a group of cylinders)

2021 ◽  
Vol 263 (3) ◽  
pp. 3714-3719
Author(s):  
Takamasa Sato ◽  
Shuichi Sakamoto ◽  
Isami Nitta ◽  
Shunsuke Unai ◽  
Takunari Isobe ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Propagation Constant ◽  
Characteristic Impedance ◽  
Physical Property ◽  
Sound Absorption Coefficient ◽  
Accurate Estimation ◽  
Sound Waves ◽  
Acoustic Characteristics ◽  
Measuring Tube

In this study, we conducted theoretical analyses and experiments related to the acoustic characteristics of the situation where sound waves are incident upon the side surfaces of a group of cylinders forming a pin-holder structure. The sound-absorption coefficient, entering its clearance between cylinders through the geometrical dimension of the clearance or the physical property of gas, was calculated. In the analytical model, the gap part of the pin-holder structure was divided into elements and approximated as a gap surrounded by two parallel planes. The characteristic impedance and propagation constant of the approximate gap were obtained and treated as one-dimensional transfer matrices; the sound-absorption coefficient was then calculated using the transfer-matrix method. The calculated value was compared to that obtained in an experiment with a sample prepared using a 3D printer; the sound-absorption coefficient was measured using a 2-microphone impedance-measuring tube. We attempted to make a simple yet accurate estimation of sound-absorption coefficient using these procedures. Our theoretical values displayed a similar tendency to that obtained by experiment.

Transmission Line Theories for the Analysis of Electromagnetic Transients in Coil Windings

2013 ◽  
pp. 1-44
Author(s):  
Akihiro Ametani ◽  
Teruo Ohno
Keyword(s):  
Transmission Line ◽  
Propagation Constant ◽  
Characteristic Impedance ◽  
Electromagnetic Transients ◽  
Distributed Parameter ◽  
System A ◽  
Three Phase ◽  
Distributed Parameter Circuit ◽  
Transformer Winding ◽  
Phase Transmission

The chapter contains the basic theory of a distributed-parameter circuit for a single overhead conductor and for a multi-conductor system, which corresponds to a three-phase transmission line and a transformer winding. Starting from a partial differential equation of a single conductor, solutions of a voltage and a current on the conductor are derived as a function of the distance from the sending end. The characteristics of the voltage and the current are explained, and the propagation constant (attenuation and propagation velocity) and the characteristic impedance are described. For a multi-conductor system, a modal theory is introduced, and it is shown that the multi-conductor system is handled as a combination of independent single conductors. Finally, a modeling method of a coil is explained by applying the theories described in the chapter.

Transmission Line

2020 ◽  
pp. 43-71
Keyword(s):  
Transmission Line ◽  
Transmission Lines ◽  
Magnetic Energy ◽  
Propagation Constant ◽  
Characteristic Impedance ◽  
Electric Energy ◽  
Electromagnetic Energy ◽  
The Other ◽  
Electrical Characteristics ◽  
Lumped Elements

A transmission line (TL) is simply a medium that is capable of guiding or propagating electromagnetic energy. The transmission line stores the electric (E) and magnetic (M) energies and distributes them in space by alternating them between the two forms. This means that at any point along a TL, energy is stored in a mixture of E and M forms and, for an alternating signal at any point on the TL, converted from one form to the other as time progresses. Transmission line is usually modelled using lumped elements (i.e., inductors for magnetic energy, capacitors for electric energy, and resistors for modelling losses). The electrical characteristics of a TL such as the propagation constant, the attenuation constant, the characteristic impedance, and the distributed circuit parameters can only be determined from the knowledge of the fields surrounding the transmission line. This chapter gives a brief overview of various transmission lines, with more detailed discussions on the microstrip and the SIW.

A Study of Characteristic Signal Propagation Buried Pipeline 2

2010 ◽  
Vol 36 ◽  
pp. 387-394
Author(s):  
Hisashi Oohira ◽  
Serikawa Seiichi
Keyword(s):  
Propagation Constant ◽  
Characteristic Impedance ◽  
Signal Propagation ◽  
Measuring System ◽  
Long Distance ◽  
Actual Measurement ◽  
Fault Resistance ◽  
System A ◽  
Characteristic Signal ◽  
Heavy Construction

It was reported in the previous report that the propagation constant measuring system for long distance pipelines was produced based upon the distribution constant theory for the purpose of maintenance and management of long distance pipelines buried underground and to have a system to directly measure the propagation constants and characteristic impedance of the pipeline buried underground. This time, a simulator for the signal propagation of a pipeline, referring to these actual measurement values, was constructed and various signal modes were simulated. On the prediction of accidents where heavy-construction equipment, such as backhoe or boring machine, has contact with a pipeline and damages the coating of pipeline, the damage simulations with a backhoe and boring machine were performed and the fault resistances of these heavy-construction pieces of equipment at the time of accidents were identified. As a result, it was revealed that the fault resistance generated by the metal-to-metal contact caused by the boring machine, which damages pipeline the most, was approximately 20-50Ω when water was used, and that caused by the backhoe was approximately 100Ω. In order to verify the detectable property of this system, a simulation was performed to determine how each distributed constant changed when this degree of grounding faults occurred in the monitoring section of the pipeline, and validated it with an actual pipeline.

Electromagnetic Wave Propagation

2020 ◽  
pp. 78-88
Author(s):  
Magdalene Wan Ching Goh
Keyword(s):  
Wave Propagation ◽  
Electromagnetic Wave ◽  
Electromagnetic Radiation ◽  
Electromagnetic Wave Propagation ◽  
Propagation Constant ◽  
Characteristic Impedance ◽  
Helmholtz Equations ◽  
Basic Principles ◽  
Atmospheric Windows

Electromagnetic wave propagation is an invisible phenomenon that cannot be detected by the human senses. To understand wave propagation, one must first learn what wave propagation is and the basic principles that affect wave propagation. This chapter introduces the atmospheric windows which allow electromagnetic radiation from bands to penetrate Earth. Helmholtz equations, i.e. the equations which govern wave propagation, and the properties of waves (such as propagation constant and characteristic impedance) are then briefly explained. When waves encounter different media during its propagation, they may be reflected, refracted, or diffracted. These phenomena are also covered. The last part of this chapter concisely explains the terminologies commonly used to describe electromagnetic radiation.

Boundary Element Prediction of Sound Propagation in Ducts Containing Bulk Absorbing Materials

1998 ◽  
Vol 120 (4) ◽  
pp. 976-981 ◽  
Author(s):  
A. F. Seybert ◽  
R. A. Seman ◽  
M. D. Lattuca
Keyword(s):  
Boundary Element ◽  
Sound Propagation ◽  
Propagation Constant ◽  
Characteristic Impedance ◽  
Normal Incidence ◽  
Test Method ◽  
Cavity Method ◽  
Rectangular Duct ◽  
Complex Characteristic ◽  
Foam Filled

In this paper the sound propagation in a rectangular duct containing a bulk absorbing foam liner is investigated. The foam is characterized by the complex characteristic impedance and propagation constant which are measured using an improved two-cavity method. These quantities are used to predict the normal incidence impedance and absorption coefficient of the foam which is compared to measured data obtained using the ASTM E-1050 test method. The complex characteristic impedance and propagation constant are also used to predict the attenuation through a layer of foam in a plane-wave tube for which measured results are also available. Finally, the boundary element method is used to predict the attenuation of sound in a rectangular duct where one surface is replaced by a foam-filled cavity. Comparison with experiment is shown for several frequencies.

Sign in / Sign up

Export Citation Format

Share Document