Predicted Absorption Performance of Cylindrical and Rectangular Permeable Membrane Space Sound Absorbers Using the Three-Dimensional Boundary Element Method

Abstract

Three-dimensional, permeable membrane space sound absorbers have been proposed as practical and economical alternatives to three-dimensional, microperforated panel space sound absorbers. Previously, the sound absorption characteristics of a three-dimensional, permeable membrane space sound absorber were predicted using the two-dimensional boundary element method, but the prediction accuracy was impractical. Herein, a more accurate prediction method is proposed using the three-dimensional boundary element method. In the three-dimensional analysis, incident waves from the elevation angle direction and reflected waves from the floor are considered, using the mirror image. In addition, the dissipated energy ratio is calculated based on the sound absorption of a surface with a unit sound absorption power. To validate the three-dimensional numerical method, and to estimate the improvement in prediction accuracy, the results are compared with those of the measurements and two-dimensional analysis. For cylindrical and rectangular space sound absorbers, three-dimensional analysis provides a significantly improved prediction accuracy for any shape and membrane sample that is suitable for practical use.

Application of Paper Folding Technique to Three-Dimensional Space Sound Absorber with Permeable Membrane: Case Studies of Trial Productions

“…10 This shape is applicable to 3-D PMA, and is particularly easy to apply to cylindrical 3-D PMA, to offer better designability and luminescence distribution for the aesthetic benefit of sound absorbing technique. 5,6…”

“…4 Therefore, in order to determine the expected absorptivity value of the test specimen, we made a BEM simulation for a cylindrical 3-D PMA (without folding) to give a first approximation of expected absorptivity of the test specimens made of the selected material. 6 The method of the BEM simulation was detailed in Toyoda et al 6 As is shown in Fig. 5 of subsequent section, the result of the simulation, with the parameters of the selected material above, showed that the selected material can offer moderately high sound absorptivity, i.e., around 0.5 to 0.6 at middle and high frequencies.…”

“…3,4 Recently, the authors proposed space sound absorbing systems using PMs, including textiles and woven or non-woven fabrics, which are constructed in a three-dimensional object such as a cylinder, rectangle, or plane, and studied their sound absorbing characteristics experimentally as well as analytically and numerically with boundary element method (BEM) simulations. [5][6][7] The results showed that these membrane space sound absorbers offer moderate sound absorptivity, about 0.5-0.6 at maximum, in the middle to high frequency ranges, depending on the absorber's parameters and conditions. Therefore, it was confirmed that these space absorbers can be effectively used in some situations.…”

Sound Absorption of Sustainable Polymer Nanofibrous Thin Membranes Bonded to a Bulk Porous Material

“…All these numbers show that sound absorbing materials based on fiberglass and mineral wool report high environmental impacts, mainly due to their embodied energies [3]. Moreover, Toyoda et al [4] have pointed out some of the environmental drawbacks of using fiberglass as a sound-absorbing material, including durability issues, difficult recycling, and that its dust is harmful to humans. The acoustic characterization of green materials has been discussed by Iannace [5] and a comprehensive review on acoustical eco-materials can be found in [2].…”

“…The statistical sound absorption coefficients of permeable membranes of different airflow resistance and sizes have been presented more recently [12]. On the other hand, Toyoda et al [4] have presented a numerical method to predict the sound absorption performance of cylindrical and rectangular permeable membrane space sound absorbers. Kalinova [9] has demonstrated that the nanofibrous layer has a resonant effect on sound absorption when the nanofibers are arranged with respect to the layer.…”