Abstract
Curtailment of the ambient noise level for providing a better living environment is immensely important. Accordingly, acoustic isolation via different combinations of porous materials is the most widely used passive soundproofing system. The present study focuses on the optimization of single and double-layer absorbers in different frequencies. To this end, the transfer matrix and the Evolution Strategy (ES) method are firstly explained. Afterward, the optimization of single and double-layer absorbers is considered for up to 10 parameters (material porosity, air gap, perforated plate characteristics among others) at 350 Hz frequency and has been compared with the results obtained through other methods (Genetic Algorithm among others). It has been illustrated that ES algorithm provides better optimization in this field. Subsequently, since the incident sound in most cases is a correlation of different frequencies, the broadband optimization of the single and double-layer absorbers is considered in three frequency ranges (100–800 Hz, 800–1600 Hz, 1600–3000 Hz), with an increment of 1 Hz, for three different materials (polyester, fiber and foam). After the optimization, the resulting optimum parameters are presented in form of characteristics charts of the optimized materials for different frequency ranges, as a reference for material designers and manufacturers. Also, the absorption coefficient of all optimized cases are calculated and presented in range of 100 Hz to 3 kHz as a reference for the absorber selection for different situations. Finally, by presenting the improvement chart of double layer versus single layer combinations, it has been shown that double layer combination can improve the absorption coefficient of different materials up to 4% in different frequencies depending on the material (4% for polyester and foam for under 800 Hz, 3–4% for polyester and fiber for 800–1600 Hz and 2.6% for foam in 1600–3000 Hz).
Highlights
In 1970, the World Health Organization (WHO) carried out an assessment about the global disease burden from the occupational noise in which the noise characteristics and their relevance to workers’ health were studied and quantified
Transfer Matrix approach and Evolution Strategy (ES) algorithm are used in order to achieve an optimized design for single and double-layer formations for Foam, Fiber and Polyester porous absorbers with maximum sound absorption
This comparison proves that the ES algorithm offers favorable results based on the limitations that are imposed on the design problem with superiority over the absorption coefficient obtained by the widely used method of Genetic Algorithm
Summary
In 1970, the World Health Organization (WHO) carried out an assessment about the global disease burden from the occupational noise in which the noise characteristics and their relevance to workers’ health were studied and quantified. It was proved that high level of environmental noise in a working area is the main cause of worker’s psychological and physiological diseases [1] It has always been a challenge for engineers to design an optimized sound absorber in order to obtain suitable absorption in a broadband frequency range [2]. Different arrangements of porous layers have been studied by Lee et al [24] in order to achieve maximum transfer loss based on topology method In another attempt, Lee et al [25] optimized two-dimensional foams for maximum sound absorption. Different characteristics of single-layer and double-layer sound absorbers are optimized to obtain the best absorption coefficients This is done at three different frequency bands for three different porous materials of foam, fiber and polyester, using transfer matrix and ES optimization method. The mathematical formulation of transfer matrix method and the Evolution Strategy is presented, followed by the optimization of single and double layer combinations of foam, fiber and polyester
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