Typo: should have been -1.9 dB (now corrected in my original post.
Select all, then “Effect > Amplify” shows the peak amplitude to be -1.9 dB.
or install this “show peak amplitude” plugin Peak Amplitude (Analyze plug-in) which shows the peak amplitude to be -1.87 dB.
For 100 ms window rms:
Select a “noise only” section.
Nyquist Prompt effect.
(linear-to-db (peak (rms s) ny:all))
Repeat for a couple of other “noise only” sections to check.
For a window size equal to the selection length, same procedure as above but replace the code with:
(let ((step (truncate len))
(s-sq (mult s s)))
(linear-to-db
(snd-fetch
(snd-sqrt
(snd-avg s-sq step step op-average)))))
Or as Gale suggested: “Analyze > Contrast”
Alternatively, use this “wave stats” plug-in: "Wave Stats" plug-in which gives you peak, rms, and DC offset measurements.
Interesting to note that each of these rms measurements give slightly different values, but they are all in the same ballpark.
I used 100 Hz 12 dB/Octave.