the dvm probably measures rms ac voltage. the accuracy of that measurment decreases with frequency. at 60 hz rms voltage is [2^0.5]/2 of the peak voltage. i think your 2.83v is really 2.83/0.707 peak voltswith pink noise (equal power in each octave?) you've got a bunch of frequencies, not a single sine wave, so i can't begin to guess how the rms value relates there.
just a little rambling from what little i think i know ;-^