1. A method of processing a set of input data X(v) representing a desired signal component plus an undesired contamination component, the method comprising the following steps: obtaining an ensemble-averaged power spectrum of the signal component, <&verbar;K S (v)&verbar; 2 >; obtaining an ensemble-averaged power spectrum of the contamination component, <&verbar;K N (v)&verbar; 2 >; forming a term B 2 &equals;<&verbar;K N (v)&verbar; 2 >/<&verbar;K S (v)&verbar; 2 >; forming a filter function W(v), where &verbar;W(v)&verbar;&equals;&lsqb;1&plus;b 2 B(v) 2 &rsqb; −1, and b is greater than zero; forming a term U(v), where &verbar;U(v)&verbar;&equals;&lsqb;W(v)(1−W(v))&rsqb; ½ ; and processing X(v) to form a result U(v) X(v).