Experimental Studies on the Sound Absorbing Materials by Using of the Bundle of Narrow Clearances between Two Planes

Shuichi SAKAMOTO, Kazuyuki SAITO, Nobuaki MURAYAMA, Katsuya HIGUCHI
2013 Transactions of the Japan Society of Mechanical Engineers Series C  
In this study, the sound-absorption coefficients of the sound-absorbing structure using bundle of narrow clearances between a number of thin plates were measured for various formations and size. It is found by the experiment that, when the clearance between thin plates is reduced, the peak sound absorption value is increased and the frequency decreases. This phenomenon is related to velocity boundary layer thickness. Therefore, its occurrence is limited to clearances of 70 microns or more. When
more » ... crons or more. When the clearances decrease in depth, the absorption coefficient is high compared with the case where clearances remain constant. This decrease also tends to improve the dip in the frequency characteristic curve of the absorption coefficient. However, when the clearances change to lateral direction continuously, this dip is not improved. When the amounts of materials constituting thin plates are identical, sound absorption performance of a folding-fan-type sound-absorbing structure is equivalent to a wedge-shaped sound-absorbing structure.
doi:10.1299/kikaic.79.4141 fatcat:ox3qrkifljhivg3ey3z65lzmlu