A Model Updating Technique Based on the Constitutive Relation Error for In Situ Identification of Admittance Coefficient of Sound Absorbing Materials

Abstract

The development of new absorbing materials and the description of their acoustical properties take an important place in the current acoustical researches. This paper focuses on the identification of the admittance coefficient of sound absorbing material from in situ measurements, using the constitutive relation error (CRE)-based updating technique. This technique consists of a two-stage approach, allowing to regularize the inverse problem. Moreover, the technique allows the detection of faulty sensors and therefore the correction of the erroneous measurements before the updating process. The technique is developed, in a first part of this paper, for acoustical problems with generalized boundary conditions, and illustrated, in a second part, on a numerical and a physical two-dimensional (2D) test case.

Assessment of the Measurement and Prediction Methods for the Acoustic Properties of Natural Fiber Samples and Evaluation of Their Properties

“…According to these measurements, the quantities k and Z c depend mainly on the frequency ω and on the flow resistivity σ of the porous media. A proper fit of the measured values of k and Z c was obtained with the following expressions (Progneaux, Bouillard, and Deraemaeker 2015):…”

“…In the case of multiple layers, Miki (1990) recognized that the real part of the surface impedance when computed with the Delany-Bazley model sometimes becomes negative at low frequencies (indicating a nonphysical result), and new coefficients were proposed. The so-called Delany-Bazley-Miki model has the same formula structure as the Delany-Bazley model; however, the coefficients (c 1 , c 3 , c 5 and c 7 ) and the degrees (c 2 , c 4 , c 6 and c 8 ) are different (Progneaux, Bouillard, and Deraemaeker 2015). The Delany-Bazley-Miki model regression constants are listed in Table 3.…”