The increase in acoustic power output of a constant‐strength point monopole caused by boundaries can be found directly from the value of the imaginary part of the reflected pressure at the source. Waterhouse obtained an expression for the power output of a source by assuming that the plane could be specified by a pressure‐reflection coefficient (R) that is Independent of the angle of incidence. It is shown here that for some geometries the power output is independent of the angular dependence ofR. When the source is located over an infinite plane, the increase in acoustic power output can also be found by using admittance boundary conditions. Some solutions are presented for this configuration and are compared with the results obtained by Waterhouse.