BSTRACTWe developed a sound absorber using a magnetorheological fluid(MR-F) based on the density and alignment angle of carbonyl iron powder(CIP) chains by the controlling the magnetic field strength and direction. The magnetically arranged CIP lattice structure considerably influenced the sound transmission loss(STL). We used optical microscopy

energy-dispersive X-ray spectrometry

and X-ray diffraction to investigate the STL by varying the magnetic field strength from 0 to 40 mT and the angle from 0 to 30°. The STL was markedly increased (133%) owing to an ∼10-fold increased density and the CIP alignment. These results were verified using the developed MR-F porous model.