# RN,PI Spectrum

The RN,PI (Random Noise, Periodic Interference) Spectrum graph provides additional insights into the noise measurements. It is a qualitative tool only; the noise spectrum is aliased and the vertical axis is not labeled.

Because the signal is under-sampled, all periodic components are aliased down below 20 kHz. The RN (Random Noise) is calculated as the area of the power spectral density excluding any peaks in the spectrum (for example, the baseline noise of the power spectral density).