  We consider the propagation of time harmonic acoustic waves in a device with
three channels. The wave number is chosen such that only the piston mode can
propagate. The main goal of this work is to present a geometry which can serve
as an energy distributor. More precisely, the geometry is first designed so
that for an incident wave coming from one channel, the energy is almost
completely transmitted in the two other channels. Additionally, tuning a bit
two geometrical parameters, we can control the ratio of energy transmitted in
the two channels. The approach is based on asymptotic analysis for thin slits
around resonance lengths. We also provide numerical results to illustrate the
theory.
