Scattering-Matrix Formulation for Both Measurement and Prediction of Acoustical Performances of Hybrid Cells and Their Active and Passive Elements

Abstract

The design of panels improving both sound absorption and insulation performance overawide frequencyrange is ap roblem of considerable practical interest for transport and building industries. In this work, an analytical method for predicting both the absorption coefficient and the transmission loss of hybrid active/passive multilayered cells and the associated experimental investigation are presented. These cells combine passive and active control by using passive layers and an active plate. Passive layers consist of absorbing materials located on the reception side in order to increase absorption overawide frequencyrange. The active plate vibrates as asecondary source in order to reduce sound transmission at lowand/or at resonance frequencies. To validate the analytical approach, measurement methods in ducts based on the scattering-matrix description are applied to characterise three types of system: (i)-passive discontinuities such as multilayered sandwiches including porous layers (ii)-active discontinuities here the active plate playing the secondary source role, (iii)-hybrid cells equipped with active control system. Forthese three cases, the correspondence between theoretical simulations and experimental results is satisfactory.

Archives of Acoustics

“…To characterize the acoustic behavior of duct discontinuities with rigid wall and lined parts, numerous methods were proposed like the work of Miles (1946), Peat (1988a;1988b), Munjal (1987), Kergomard and Garcia (1987), Amir et al (1996) and Selamet et al (2004). To evaluate the acoustic performance of ducts systems, different matrices were used such as the transfer matrix (Peat, 1988a;Munjal, 1987;Craggs, 1989), reflection matrix (Akoum, Ville, 1998;Sitel et al, 2003), transmission matrix (Sitel et al, 2003) or multimodal scattering matrix (Åbom, 1991;Leroux et al, 2003;Bi et al, 2006;Sitel et al, 2006). The latter matrix showed its efficiency in modeling duct elements and liner impedance at higher-order modes.…”

Adaptive metamaterials for broadband sound absorption at low frequencies

“…The major advantage of the absorptive structure is the deep-subwavelength size with the thickness less than the operating wavelength by up to two orders of magnitude [8,9]. In the current design, the active strategy, which has been widely implemented previously [19][20][21][22][23], is employed to render tunable peak absorption frequencies as an attempt to extend the bandwidth of the total acoustic absorption. To this end, two piezoelectric films (PZT-5H) of thickness 0.2 mm with the shunting circuits are bonded on both sides of the aluminum membrane.…”

“…Tunable sound absorption using active materials and structures has been studied for a long time [18][19][20][21][22][23][24][25][26][27]. The active sound cancelation technique is the method for eliminating unwanted sounds by an additional feedforward control power source [18].…”

“…When the micro-perforated panel was made by flexible Polyvinylidene fluoride piezoelectric film, sound absorption could be also improved by using the shunt-damping technology [21]. Hybrid multilayered cells consisting of porous damping material and piezoelectric plate were investigated, in which active control has been proved to enhance sound transmission loss and absorption [22,23]. Acoustic absorbing systems designed with active materials have shown great potentials in the damping enhancement.…”