Influences of Compression Ratios on Sound Absorption Performance of Porous Nickel–Iron Alloy

Abstract

Abstract:The improvement of sound absorption performance of porous metal is a focus of research in the field of noise reduction. Influences of compression ratios on sound absorption performance of a porous nickel-iron (Ni-Fe) alloy were investigated. The samples were compressed with ratios from 10% to 80% at an interval of 10%. Based on the standing wave method, sound absorption coefficients of compressed samples with different thicknesses were obtained. It could be found that with the same compression ratio, sound absorption performance was improved with the increase of thickness. Based on the modified Johnson-Allard model with a correction factor, the sound absorption coefficient of the porous Ni-Fe with a thickness of 20 mm for different compression ratios was derived, whose aim was to quantificationally analyze influences of the compression ratio. The results indicated that the sample with a compression ratio of 70% exhibited optimal sound absorption performance, and its average sound absorption coefficient reached 88.97% in a frequency range of 1000-6000 Hz. Meanwhile, the section morphologies of compressed samples were investigated by a scanning electron microscope, which studied the sound absorption performance by analyzing structures of the porous Ni-Fe samples with different compression ratios. The obtained achievements will promote the application of the porous Ni-Fe alloy in the field of acoustics.

Improving and Optimizing Sound Absorption Performance of Polyurethane Foam by Prepositive Microperforated Polymethyl Methacrylate Panel

“…Meanwhile, when the frequency range was 100-2000 Hz, the absolute value and relative percentage of improvement of the theoretical average sound absorption coefficient fell from 0.3690 and 247.76% to 0.1050 and 15.44% respectively with thickness of the polyurethane foam increased from 10 mm to 40 mm. The major reason for this phenomenon was that sound absorption performance of the polyurethane foam in the entire frequency range was raised when its thickness rose, which was consistent with normal absorption property of the porous material [15][16][17]31,33,35]. Comparisons of theoretical data, simulation data, and experimental data of the sound absorption coefficients of the composite sound-absorbing structure are shown in Figures 9 and 10 respectively.…”

“…Judging from theoretical sound absorption mechanism of the microperforated panel absorber [18][19][20], it could be found that its sound absorption performance was determined by its geometric parameters and had little to do with its physical or chemical parameters. Owing to the investigated frequency ranges of 100-1000 Hz and 100-2000 Hz, the diameter of the prepared composite structures was 96 mm, which satisfied the requirement of the utilized AWA6128A detector for standing wave tube measurement of the sound absorption coefficients [33,35]. Through replacing the detected polyurethane foam by the prepared composite structure in Figure 4, actual sound absorption coefficients of the composite sound-absorbing structures were tested, which could provide experimental validation of the identification and optimization results.…”

“…The investigated polyurethane foam samples in this study were purchased from the GreenCARE International (Guangzhou) Ltd., Guangzhou, Guangdong, China. Sound absorption coefficients α a of the polyurethane foam were achieved by the AWA6128A detector (Hangzhou Aihua instruments Co., Ltd., Hangzhou, Zhejiang, China) based on the standing wave tube measurement [32][33][34][35], which acted in accordance with the ISO 10534-1: 1996 Acoustics-Determination of sound absorption coefficient and impedance in impedance tubes-Part 1: Method using standing wave ratio and the ISO 10534-2: 1998 Acoustics-Determination of sound absorption coefficient and impedance in impedance tubes-Part 2: Transfer-function method [36,37]. In order to improve the accuracy of the identification and examine the effectiveness of the identified acoustic characteristic parameters, the polyurethane foam samples with thicknesses of 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm were measured, and the selected frequency range was [100 Hz, 6000 Hz] with an interval of 100 Hz.…”

“…Through replacing the detected polyurethane foam by the prepared composite structure in Figure 4, actual sound absorption coefficients of the composite sound-absorbing structures were tested, which could provide experimental validation of the identification and optimization results. Moreover, in order to decrease the accidental measuring error in the testing program, each composite structure was tested 10 times, and the final experimental data was the average value of the 10 tests Owing to the investigated frequency ranges of 100-1000 Hz and 100-2000 Hz, the diameter of the prepared composite structures was 96 mm, which satisfied the requirement of the utilized AWA6128A detector for standing wave tube measurement of the sound absorption coefficients [33,35]. Through replacing the detected polyurethane foam by the prepared composite structure in Figure 4, actual sound absorption coefficients of the composite sound-absorbing structures were tested, which could provide experimental validation of the identification and optimization results.…”

“…Afterwards, identification of acoustic characteristic parameters of the polyurethane foam and optimization of structural parameter of the composite structure were realized through the cuckoo search algorithm [24][25][26][27]. Later, the composite structure was verified by the finite element simulation method [28][29][30][31] and validated through the standing wave tube measurement [32][33][34][35]. Finally, the accuracy of identified acoustic characteristic parameters of the polyurethane foam and effectiveness of improved sound absorption performance of the composite structure were proved.…”