the SMPTE pink noise) will have peaks at -8 dBFS, as that noise has a 12 dB crest factor. Using the RMS reference, a -20 dBFS sine wave will have peaks at -17 dBFS as there's a 3 dB crest factor in sine waves, and a -20 dBFS pink noise (i.e. Speakers don't do square waves all that well, and neither do magnetic or optical analog film soundtracks, so sine waves are the reference.Ĭircling back to your post, when a -20 dBFS sine wave has peaks at -20 dBFS, that shows the meter and/or signal generator is in the peak reference mode. And there would be no optimal way to produce a 0 dBFS signal acoustically, as only a pure square wave would reach 0 dBFS. If we were to use the alternative peak reference, 85 dB would occur with -23 dBFS signals. In the world we inhabit around here wrt signals that translate to SPL, we ought to use the same (RMS) scale as the film industry, as they define reference SPL as 85 dB for -20 dBFS signals. In each case, a well defined signal represents 0 dBFS. One scale is better for electrical measurement (the peak scale) while the other is better for acoustic measurements (the RMS scale).

Programs like Audacity, Adobe Audition, and Room EQ Wizard, allow the user to select which reference they prefer. One is the peak value of a sine wave, and the other is the RMS value of a sine wave. On top of that, there's two references for 0 dBFS.

An interesting caveat being a standard PPM (peak program meter) will show that a -20 dBFS sine wave will have peaks -20.on the other hand -20 dBFS pink noise will have relatively constant peaks at approximately -10 dBFS.

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