A signal generator generates amplitude noise on a selected segment of a test signal. A user interface is used for selecting a segment of the test signal and an associated power level for applying amplitude noise at a selected power level to the test signal segment. A signal processing unit compiles the selected power level of the selected segment with the test signal to generate digital data representative of the test signal with selected segments having amplitude noise. A waveform generator receives the digital data and generating a test signal output having amplitude noise at selected segments of the test signal. The method includes the steps of: selecting a segment of the test signal to add amplitude noise; selecting a power level for the amplitude noise; and applying the amplitude noise at the selected power level to the selected segment of the test signal.