Abstract
The static flow resistivity is a fundamental parameter for measuring and classifying the sound absorption behavior of various types of materials. Several methods have been developed for measuring the static flow resistivity acoustically. Most of these methods cannot be implemented directly in the standard tubes which are widely used for measurements of sound absorption coefficients and impedance as defined in ISO 10534.2. The accuracy of the proposed method and the tube is verified through finite element analysis and the feasibility to determine the static flow resistivity is validated through experiments. It is validated that the accuracy of the proposed method is highly dependent on the position of the acoustic center of the measurement microphones and the accuracy can be enhanced by increasing the back cavity depth and/or decreasing the measurement frequency.
Highlights
Sound absorbing materials are essential considerations in building acoustics and noise reduction in the environment
Woodcock et al [11] measured the propagation constant and the characteristic impedance of the material by adopting two-cavity method and calculated the effective flow resistivity using the inverse equation of the Delany and Bazley empirical formulae [12]
For obtaining the static flow resistivity, the sound pressure has to be measured from the front side of the specimen on the rigid termination La and Lb respectively in dB
Summary
Sound absorbing materials are essential considerations in building acoustics and noise reduction in the environment. The normal sound absorption coefficient and the surface impedance of a material are often measured by an impedance tube [1] [2] These properties include complex characteristic impedance, complex propagation constant, and random incidence absorption coefficient. The flow resistivity plays a major role in the calculation of acoustic properties of materials like propagation constant, sound absorption and characteristic impedance. McIntosh et al [10] proposed to measure the sound pressure at both sides of the test specimen, and divided the sound pressure drop by the flow velocity and the specimen thickness to calculate the static flow resistivity. Woodcock et al [11] measured the propagation constant and the characteristic impedance of the material by adopting two-cavity method and calculated the effective flow resistivity using the inverse equation of the Delany and Bazley empirical formulae [12]. Jiancheng Tao et al [13] found out that a thicker specimen provides more stable flow resistivity and allows a higher measurement frequency
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