 Several examples will be provided to illustrate the effectiveness of DAT and compact finite difference schemes in numerically solving heterogeneous Helmholtz equations with variable wave numbers.
<clarity>  Several examples will be provided to illustrate the effectiveness of DAT and compact finite difference schemes in numerically solving heterogeneous Helmholtz equations with variable wave numbers.
 Several numerical examples are provided to illustrate the effectiveness of DAT and compact finite difference schemes in numerically solving heterogeneous Helmholtz equations with variable wave numbers.