This paper presents the development and performance of micro-perforated panels(MPP)from natural fiber reinforced composites.The MPP is made of Polylactic Acid(PLA)reinforced with Oil Palm Empty Fruit Bunch Fiber(OPEFB...This paper presents the development and performance of micro-perforated panels(MPP)from natural fiber reinforced composites.The MPP is made of Polylactic Acid(PLA)reinforced with Oil Palm Empty Fruit Bunch Fiber(OPEFBF).The investigation was made by varying the fiber density,air gap,and perforation ratio to observe the effect on the Sound Absorption Coefficient(SAC)through the experiment in an impedance tube.It is found that the peak level of SAC is not affected,but the peak frequency shifts to lower frequency when the fiber density is increased.This phenomenon might be due to the presence of porosity in the inner wall of the holes.Increasing or decreasing the air gap and perforation ratio shifts the peaks of acoustic absorption either way.展开更多
A new acoustic barrier structure with resonant sound of micro-perforation board absorption structure and impedance composite sound-absorption structure is proposed.The acoustic impedance and the sound-absorption coeff...A new acoustic barrier structure with resonant sound of micro-perforation board absorption structure and impedance composite sound-absorption structure is proposed.The acoustic impedance and the sound-absorption coefficient of the acoustic structure are calculated via means of equivalent circuit.MATLAB is used to calculate the relationship between the parameters of the ontology structure and the sound-absorption coefficient and the sound insulation.It is revealed that the sound barrier of the new ontology structure is 7.659.80 dB,which is more than the sound barrier of the traditional reflective structures.The relationships among the parameters of sound-absorption structure,sound-absorption coefficient,and sound insulation performance are obtained.In addition,the parameters can be transformed to satisfy the noise reduction requirements of various road sections,which has a admirable adaptability.The acoustic barrier can have tremendous acoustic performance only if there is a splendid sound insulation in the traffic noise frequency band.展开更多
The multilayer impedance composite sound absorption structure of the new muffler is proposed by combining the microporous plate structure with the resonant sound absorption structure of the porous material.Firstly,the...The multilayer impedance composite sound absorption structure of the new muffler is proposed by combining the microporous plate structure with the resonant sound absorption structure of the porous material.Firstly,the acoustic impedance and acoustic absorption coefficient of the new muffler structure are calculated by acoustic electric analogy method,and then the noise attenuation is calculated.When the new muffler structure parameters change,the relationship among the noise frequency,the sound absorption coefficient and the noise attenuation is calculated by using MATLAB.Finally,the calculated results are compared with the experimental data to verify the correctness of the theoretical calculation.The variation of resonance peak,resonance frequency and attenuation band width of each structural parameter is analyzed by the relation curve.The conclusion shows that it is feasible to use multilayer sound absorbing materials as the body structure of the new muffler.And the influence relationship between the change of various parameters of the sound absorption structure with the sound absorption coefficient and noise attenuation is obtained.展开更多
A composite absorber made of a polyurethane sponge and multi-layer micro-perforated plates is pre-sented in this study.Results from an acoustic impedance tube test show that the polyurethane sponge can exhibits higher...A composite absorber made of a polyurethane sponge and multi-layer micro-perforated plates is pre-sented in this study.Results from an acoustic impedance tube test show that the polyurethane sponge can exhibits higher low-frequency sound absorption in front of the micro-perforated plate,while sound absorption at medium and high-frequencies remains low.The physical mechanism behind this is that the micro-perforated plate increases the denpth cavity.If the polyurethane sponge is placed behind the micro-perforated plate,the amplitude of the original absorption peak will remain constant,but the ab-sorption peaks will shift to lower frequencies.The reason for this phenomenon is that porous materials with low flow resistance can be approximately equivalent to fluid,which not only does not affect the res-onance absorption coefficient of micro-perforated plate,but also makes the peaks move to low frequency.This study has the potential applications in the sound absorption design of composite structure.展开更多
The geometric parameters of micro-perforated panels with irregular holes cannot be directly known,making it difficult to calculate the sound absorption performance.Therefore,we propose a method of estimating the geome...The geometric parameters of micro-perforated panels with irregular holes cannot be directly known,making it difficult to calculate the sound absorption performance.Therefore,we propose a method of estimating the geometric parameters of micro-perforated panels.The irregular holes are treated as equivalent circular ones,and the model of estimating the geometric parameters is established by using Maa's theory about the panel with circular holes.The result of the parameter estimation of a type of micro-perforated panel is used to predict the absorption performance,resulting in good agreement with experiments.According to the influences of the geometric parameters of the panel on the high absorption region,we discuss the relationship between the application limit of Maa's theory and the geometric parameters,and investigate the evolution law of the sound absorption performance when the panel is polluted by dust.If the parameters of the panel are designed near the center of the high absorption region,large value of the application limit of Maa's theory can be obtained;and if the parameters are located in the upper right part of the high absorption region,a certain degree of dust pollution of the panel does not decrease the sound absorption performance.展开更多
基金sponsored by Taylor’s University Flagship Research Grant TUFR/2017/001/05。
文摘This paper presents the development and performance of micro-perforated panels(MPP)from natural fiber reinforced composites.The MPP is made of Polylactic Acid(PLA)reinforced with Oil Palm Empty Fruit Bunch Fiber(OPEFBF).The investigation was made by varying the fiber density,air gap,and perforation ratio to observe the effect on the Sound Absorption Coefficient(SAC)through the experiment in an impedance tube.It is found that the peak level of SAC is not affected,but the peak frequency shifts to lower frequency when the fiber density is increased.This phenomenon might be due to the presence of porosity in the inner wall of the holes.Increasing or decreasing the air gap and perforation ratio shifts the peaks of acoustic absorption either way.
基金National Natural Science Foundation of China(No.51175195)Guiding Plan of Textile Industry Federation,China(No.2017053)
文摘A new acoustic barrier structure with resonant sound of micro-perforation board absorption structure and impedance composite sound-absorption structure is proposed.The acoustic impedance and the sound-absorption coefficient of the acoustic structure are calculated via means of equivalent circuit.MATLAB is used to calculate the relationship between the parameters of the ontology structure and the sound-absorption coefficient and the sound insulation.It is revealed that the sound barrier of the new ontology structure is 7.659.80 dB,which is more than the sound barrier of the traditional reflective structures.The relationships among the parameters of sound-absorption structure,sound-absorption coefficient,and sound insulation performance are obtained.In addition,the parameters can be transformed to satisfy the noise reduction requirements of various road sections,which has a admirable adaptability.The acoustic barrier can have tremendous acoustic performance only if there is a splendid sound insulation in the traffic noise frequency band.
基金National Natural Science Foundation of China(Nos.51705545 and 15A460041)。
文摘The multilayer impedance composite sound absorption structure of the new muffler is proposed by combining the microporous plate structure with the resonant sound absorption structure of the porous material.Firstly,the acoustic impedance and acoustic absorption coefficient of the new muffler structure are calculated by acoustic electric analogy method,and then the noise attenuation is calculated.When the new muffler structure parameters change,the relationship among the noise frequency,the sound absorption coefficient and the noise attenuation is calculated by using MATLAB.Finally,the calculated results are compared with the experimental data to verify the correctness of the theoretical calculation.The variation of resonance peak,resonance frequency and attenuation band width of each structural parameter is analyzed by the relation curve.The conclusion shows that it is feasible to use multilayer sound absorbing materials as the body structure of the new muffler.And the influence relationship between the change of various parameters of the sound absorption structure with the sound absorption coefficient and noise attenuation is obtained.
基金by Aeronautical Science Foundation of China(Grant 20181553015)Foundation of Shaanxi Educational Committee(Grant 2018BSHYDZZ03)+1 种基金the National Natural Science Foundation of China(Grant 11704314)China Postdoctoral Sci-ence Foundation(Grant 2018M631194).
文摘A composite absorber made of a polyurethane sponge and multi-layer micro-perforated plates is pre-sented in this study.Results from an acoustic impedance tube test show that the polyurethane sponge can exhibits higher low-frequency sound absorption in front of the micro-perforated plate,while sound absorption at medium and high-frequencies remains low.The physical mechanism behind this is that the micro-perforated plate increases the denpth cavity.If the polyurethane sponge is placed behind the micro-perforated plate,the amplitude of the original absorption peak will remain constant,but the ab-sorption peaks will shift to lower frequencies.The reason for this phenomenon is that porous materials with low flow resistance can be approximately equivalent to fluid,which not only does not affect the res-onance absorption coefficient of micro-perforated plate,but also makes the peaks move to low frequency.This study has the potential applications in the sound absorption design of composite structure.
基金supported by the General Project of College Natural Science Research of Jiangsu Province(16KJD460002)the National Natural Science Foundation of China(51605209)
文摘The geometric parameters of micro-perforated panels with irregular holes cannot be directly known,making it difficult to calculate the sound absorption performance.Therefore,we propose a method of estimating the geometric parameters of micro-perforated panels.The irregular holes are treated as equivalent circular ones,and the model of estimating the geometric parameters is established by using Maa's theory about the panel with circular holes.The result of the parameter estimation of a type of micro-perforated panel is used to predict the absorption performance,resulting in good agreement with experiments.According to the influences of the geometric parameters of the panel on the high absorption region,we discuss the relationship between the application limit of Maa's theory and the geometric parameters,and investigate the evolution law of the sound absorption performance when the panel is polluted by dust.If the parameters of the panel are designed near the center of the high absorption region,large value of the application limit of Maa's theory can be obtained;and if the parameters are located in the upper right part of the high absorption region,a certain degree of dust pollution of the panel does not decrease the sound absorption performance.
