AbstractThe question of whether there exists an approximation procedure to compute the resonances of any Helmholtz resonator, regardless of its particular shape, is addressed. A positive answer is given, and it is shown that all that one has to assume is that the resonator chamber is bounded and that its boundary is $${{\mathcal {C}}}^2$$
C
2
. The proof is constructive, providing a universal algorithm which only needs to access the values of the characteristic function of the chamber at any requested point.