2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/74194We prove uniform Morrey-Campanato estimates for Helmholtz equations in the case of two unbounded inhomogeneous media separated by an interface. They imply weighted $L^2$-estimates for the solution. We prove also a uniform $L^2$-estimate {\em without weight} for the trace of the solution on the interfaceTo appear in Proceedings of the Royal Society of Edinburgh AAnalysis of PDEs35J05, 35B45text