Topology optimization of an acoustic horn

We present a method for topology optimization of an acoustic horn with the aim of radiating sound as efficiently as possible. Using a strategy commonly employed for topology optimization of elastic structures, we optimize over a scalar function indicating presence of material. The Helmholtz equation modeling the wave propagation is solved using the finite element method and the associated adjoint equation provides the required gradients. Numerical experiments validates that the result of the optimization provides horns with the desired acoustical properties. The resulting horns are very efficient in the frequency span subject to optimization.