Summary: We prove an estimate for the Dirichlet-Neumann operator, and for the \(H^1\) local norm for solutions of the Helmholtz equation outside an obstacle without trapping rays. We give an algorithm solving the Helmholtz equation outside a union of such obstacles. Convergence follows from this estimate. At each step of the resolution, only one obstacle is considered for itself; this defines a decomposition domain technique fitting this equation. One can use different numerical schemes, one at each step, adapted to the considered component of the obstacle; therefore, this algorithm is a hybrid computation. The results are given for two obstacles, and the generalization is straightforward.