A note on “Quasi-analytical solution of two-dimensional Helmholtz equation”

The recent paper of Van Hirtum in this journal repeats a number of misconceptions about the use of conformal mappings in solving the two-dimensional Helmholtz equation. These are discussed, as is the fact that the numerical approach presented does not lead to accurate results. In general conformal mapping is not useful in solving Helmholtz's equation. Other, accurate, techniques are briefly reviewed.