Originally Posted by JohnPM
Sort of, it is mostly the effect of the FFT which is used to generate the plot. The 50 dB (say) 'quiet' reading on an SPL meter is the total level summing across all frequencies. The waterfall plot is analysing and plotting within bands typically a fraction of a Hz wide, so the noise level in the piece between 50 Hz and 50.4 Hz (for example) is typically 20 dB or so lower than the overall 'quiet' SPL.
So, would an RTA with no source signal be the better noise floor measurement?
FYI, 46.5db was the RTA read for the attached graph.
Last edited by jim19611961; Today at 02:55 PM.