Broadband acoustical characterization in a horn shaped impedance tube

Jean-Michel Coulon , Fabien Chevillotte , François-Xavier Bécot , Luc Jaouen

Impedance tube is widely used to characterize acoustical materials, but it is restricted to frequencies corresponding to plane wave mode propagation. Broadband measurements require testing samples within tubes of different cross-sections: the smaller the diameter the higher the maximum frequency allowed. This is a critical issue for materials or multilayer samples (i) with elastic frames for which shape and size affect vibrations (ii) which can not be considered as homogeneous for small diameters. In order to cope with the paradox of testing large samples with a small tube section, an impedance adaptation is necessary. A horn above its cut-off frequency can be a good coupling element. A horn shape portion has been designed using 1D and 3D modeling for the 1.6 kHz-6.4 kHz frequency range. This approach has been validated based on comparisons against “standard” impedance tube measurements for various materials. Selected materials represent a large range of weak to important structural behavior and single to multilayer arrangements. This opens interesting perspectives for the design of broadband frequency impedance tube apparatus.

Domaines: Acoustique [physics.class-ph]

Jean-Michel Coulon, Fabien Chevillotte, François-Xavier Bécot, Luc Jaouen. Broadband acoustical characterization in a horn shaped impedance tube. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00810731⟩