Design of Underwater Impedance Tube for the Measurement of Material Acoustic Characteristics
Date Issued
2003
Date
2003
Author(s)
Chiu, Ta-Wei
DOI
zh-TW
Abstract
The thesis mainly discusses the design and fabrication of underwater impedance tube for the measurement of material acoustic characteristic. This test method can be applied to measure sound reflection coefficient, normal incidence sound absorption coefficient and specific acoustic impedance ratio of materials.
Firstly, the impedance tubes of different sizes are made according to ASTM standards and the theory of plane wave propagation. Then the theory of a transfer function method of measuring normal incident in-duct acoustic properties is presented. However, the elastic moduli and density of the tube wall and the fluid are often of similar magnitudes, and the rigid wall approximation is invalid. As a result, for example, the plane-wave mode characteristic of the rigid wall waveguide degenerates to a mode with phase velocity somewhat slower than the intrinsic sound velocity. So we study the two (ET0 and ET1) low-frequency axisymmetric propagation modes in the liquid-filled elastic tube waveguide and it is be shown for numerical calculations of modal dispersion curves and particle displacements. The properties measured with this test method are useful in basic research and product development of sound absorptive materials.
Subjects
阻抗管
Impedance Tube
Type
thesis