The procedural generation of terrain with coherent noise is a useful technique but limited in the range and realism of the terrains it can output. Often the results are repetitive. The aim of this paper is to present a method of parameterizing control of the frequency spectra of multi-octave Perlin noise allowing a greater range of terrain characteristics. The frequency spectra of the noise function are selectively attenuated with the use of a cosine function. The parameters are used to control the phase and frequency of the cosine function allowing a wide range of complex spectral characteristics of the noise function to be modulated. The result is that a more varied selection of terrain types can be generated than the standard algorithm alone. The work may be improved upon by using automated control of the filter parameters and adding additional parameters.