Almost, in all industries, acoustic noise is one of the harmful physical agents for human. In order to control noise, different methods are applied and acoustic absorption is one of the passive methods. For sound absorption wide range of absorbers are used. In recent year, perforated sheets are considered for sound absorption in industries and constructions. Usually perforated sheet are used with one of porous or fibrous materials, like rock fibers. Effective parameters on a flat perforated sheet are as follows; thickness, hole diameter, perforation ratio, and clearance of perforated plat from the solid back plate. In pyramidal perforated sheet a new parameter is defined, apex angle. Aim of this study was evaluation of apex angle effect on acoustic absorption coefficient. The first step of this study was construction of pyramidal geometry. Then, acoustic absorption coefficient measurments were carried out for apex angles of 24, 29, and 36 degree without any absorbing material.