A noise power spectrum (NPS) displays the various frequency components that comprise the noise in a time-based signal. A Fourier transform is performed on the signal to convert it from the time domain to the frequency domain. The NPS then shows the mean-square noise per unit frequency interval versus the frequency.
In this simulation background noise is simulated by adding together two sine waves with user-defined frequencies, amplitudes, and phase difference, along with Gaussian white noise. The power spectrum is calculated and both the time-based signal and the NPS are displayed.
(Reference: Ingle and Crouch, Spectrochemical Analysis, Prentice-Hall 1988)