Models and tutorials and stuff for Comsol. Files to help work with the program COMSOL Multiphysics. Year: 2011 Producer and writer: COMSOL Language: English This note is devoted to a domain decomposition method solving the Helmholtz equation in the frequency domain. This is meant for computing the acoustic profile of a cavity when forced at a given fre- quency k. This profile depends, of course , on the global geometry of the cavity, that we call here domain and denote it by Ω. Let a par- tition of the cavity Ω be given, as a union of disjoint subsets, called subdomains: Ω = ∪Ωi. We need to perform this global computa- tion as a sequence of local computations, each computation beeing performed on a single subdomain Ωi, without any knowledge of the geometry and meshing of the other subdomains. This is useful when the global geometry is too big to be stored in a single computer, or when such a computation is performed in a distributed process, each computer knowing only about the geometry of a subdomain. In order to compute the global solution via local computations, one need in- teraction conditions between subdomains, hence boundary conditions on the boundaries Γij between subdomains Ωi and Ωj . We give such boundary conditions for an iterative algorithm, prove its convergence, and show some simulations performed using Femlab and Matlab pack- ages.