Donato, PatriziaLamacz, AgnesSchweizer, Ben2020-07-172020-07-172020-06-03http://hdl.handle.net/2003/3920610.17877/DE290R-21123We analyze the Helmholtz equation in a complex domain. A sound absorbing structure at a part of the boundary is modelled by a periodic geometry with periodicity ε > 0. A resonator volume of thickness ε is connected with thin channels (opening ε^3) with the main part of the macroscopic domain. For this problem with three different scales we analyze solutions in the limit ε → 0 and find that the effective system can describe sound absorption.enHelmholtz equationsound absorbershomogenizationcomplex domain610preprint