In this study a numerical study of a suction muffler in a hermetic reciprocating compressor of a domestic refrigerator is performed using a finite volume based flow solver (Fluent). In order to reveal the behavior of the flow realistically, unsteady experimental pressure data has been used in the outlet boundary condition for the simulations. Detailed investigations are carried out to reveal the instantaneous flow behavior in different muffler sections such as channel and chambers based on the mass flow rate variation with respect to crankshaft angle. Power spectrum of pressure fluctuations at selected points help to reveal the noise characteristics of the muffler. This study gives a comprehensive insight into the interaction of muffler chambers with flow through the channel. In a previous study, the ratio of the chamber volumes were shown to be an important design parameter. To verify this assumption, three prototype muffler geometries were simulated. In these prototypes, the plate that divides the muffler into two chambers was moved by 7 mm and 10 mm in the direction to enlarge the second chamber. The flow through the prototype geometries were investigated numerically. The results showed that the aerodynamic performance increased while the aero-acoustic performance slightly decreased. Furthermore, this study aims to be an initial step to a more complicated optimization process which involves the inlet valve dynamics.