Journal ArticleDOI
Measurements of acoustic impedance in a free field with two microphones and a spectrum analyzer
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TLDR
In this article, a technique for evaluating the normal acoustic impedance at the surface of a panel of absorbing material in a free field is presented by measuring the pressure and the acoustic velocity with two microphones set very close to the panel.Abstract:
A technique is presented for evaluating the normal acoustic impedance at the surface of a panel of absorbing material in a free field. The evaluation is achieved by measuring the pressure and the acoustic velocity with two microphones set very close to the panel. This technique allows measurements of impedance for panels of area about 1 m2, the two microphones being located very close to the panel so that, contrary to other methods, the effect of the finite dimension of the panel is negligible. Because of the very small spacing between both microphones, this technique allows precise measurements only for frequencies higher than 500 Hz.read more
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Journal ArticleDOI
Surface impedance control for sound absorption: direct and hybrid passive/active strategies
TL;DR: In this paper, active and passive means are combined for the design of locally controlled absorption liners in air, whose basic principles were described by Olson and May and subsequently investigated practically by Guicking and his colleagues at the beginning of the 80's.
Journal ArticleDOI
Free field surface impedance measurements of sound-absorbing materials with surface coatings
TL;DR: In this article, surface impedance measurements of two sound-absorbing materials with surface coating are presented and compared with measurements performed in a reverberant room, in normal and oblique incidence, for these materials.
Journal ArticleDOI
A Review of the In Situ Impedance and Sound Absorption Measurement Techniques
TL;DR: The results of several studies are discussed in order to connect the ideas and insights of many authors and provide an overview of the state of the art technologies in this particular field of acoustics and the path which has led the scientific community to this point.
Combined wave and ray based room acoustic simulations of small rooms : [challenges and limitations on the way to realistic simulation results]
Marc Aretz,Michael Vorländer +1 more
TL;DR: This thesis establishes a complete framework for the combination of FEand GA-based room acoustic simulation results and discusses the inherent challenges and limitations including all aspects of sound generation, sound reflection and sound reception.
Journal ArticleDOI
Evaluation of the characteristic dimensions for porous sound‐absorbing materials
TL;DR: The concept of characteristic thermal dimension was recently introduced to predict the behavior at high frequencies of the bulk modulus of fluids saturating a porous frame as discussed by the authors, which is closely related to the specific surface of the solid porous frame.