Abstract: A frequency synthesizer for use by an operator or other means for continuously generating an output noise signal, the frequency synthesizer comprises a digital means for directly synthesizing random noise having controlled spectral amplitudes. The synthesized random noise is characterized by a series of digital composite frequency synthesizer output noise signal sample values. The digital means comprises a means for providing and for periodically changing a series of sets of shifted segment frequency values, each set of shifted segment frequency values having a controlled series of random frequency values. Each frequency value is a random digital number selected to be within a range corresponding to a segment frequency band and characterizes a shifted segment frequency value. A plurality of digital oscillators is included, each oscillator having a corresponding segment frequency band.