RMS value

[Boffin]

This very simple plug-in converts a sound into its RMS (root-mean-squared)
amplitude. The sound is windowed into 10 ms segments, the rms computed,
and the sound re-interpolated to the original sample rate.

It consists exactly of the Nyquist command:
(force-srate *sound-srate* (rms s))

The resulting "sound" is not a playable sound, but can be read as the
magnitude of the sound as a function of time. When viewed as
Waveform (dB) the dB values are equal (with a constant offset) to
the sound level, for example SPL.

This plug-in is part of a set, including RMS.ny, OctaveBand.ny, and DecayRate.ny
meant to be used to compute reverberation times over octave bands.

Boffin

[kozikowski]

When viewed as Waveform (dB) the dB values are equal (with a constant offset) to the sound level, for example SPL.

There's a loaded phrase. A "Constant Offset" given the same type of microphone with the same frequency response, polar patterns, linearity and standardized compensation curve at the same point in a room. Then, yes. You can do dBSPL like that.

Koz