Tehran University of Medical Sciences International Journal of Occupational Hygiene 2008-5109 11 3 2019 10 10 164 178 Mohammad Reza Monazzam School of Public Health and Center for Air Pollution Research (CAPR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran Zahra Hashemi Behbahan Faculty of Medical Sciences, Behbahan, Iran 2020 04 17 2020 05 03 Nowadays, micro-perforated absorbers are one of the structures that are widely used nowadays. The sound absorption mechanism is performed by viscous energy losses in the cavities on the plate. This paper examined the effect of the surface shape on the micro perforated absorber performance at low frequencies (less than 500 Hz). The three-dimensional finite element method was used to predict the absorption coefficient of this group of adsorbents. Also, the results obtained from the shaped absorbers were compared with the flat micro perforated absorbers. After validating the numerical results, six different designs were defined as the surface shape of the micro perforated plates in the COMSOL Multiphysics, Ver. 5.3a software. The results reflected the fact that the factor of the surface shape can be used as a contributing factor in some frequencies. In general, the dented or concave shapes provide better outcomes than other flat designs and shapes and the convex or outward shapes bring the weakest results. https://ijoh.tums.ac.ir/index.php/ijoh/article/view/418 https://ijoh.tums.ac.ir/index.php/ijoh/article/download/418/568