Synthesizing a friction sound of deformable objects by a computer is challenging. We propose a novel physics-based approach to synthesize friction sounds based on dynamics simulation. In this work, we calculate the elastic deformation of an object surface when the object comes in contact with other objects. The principle of our method is to divide an object surface into microrectangles. The deformation of each microrectangle is set using two assumptions: the size of a microrectangle (1) changes by contacting other object and (2) obeys a normal distribution. We consider the sound pressure distribution and its space spread, consisting of vibrations of all microrectangles, to synthesize a friction sound at an observation point. We express the global motions of an object by position based dynamics where we add an adhesion constraint. Our proposed method enables the generation of friction sounds of objects in different materials by regulating the initial value of microrectangular parameters.