Array of absorbing pyramid cones are widely used in anechoic chambers. When the period of the array is small compared with wavelength, which is in the low-frequency limit; the plane wave reflection problem is simplified and can be studied in one-dimensionally inhomogeneous media. This article deals with the optimal design parameters of pyramid cone absorbers via genetic algorithm for the normal and oblique incidence of plane wave. The optimization parameters are the dielectric permittivity and the length of the absorber over a wide frequency band and incidence angle range. The cost function of the optimization algorithm is the reflection coefficient of the absorber which is to be minimized. The algorithm is applied to different frequency bands and incidence angles. The results show that the minimized reflection coefficients and corresponding relative permittivities and absorber lengths are acceptable for each application. (C) 2008 Wiley Periodicals, Inc.