How to calculate audio rms level from basic oscilloscope image
You can also use Audacity to record audio signals and measure Spectral Analysis.

Using a sine wave on Line out and record on Line In or Aux you can use a sine to see \$V_{RMS}=V_{PK}/\sqrt2  ~~\$  or Vrms=Vpp/2.828 as @Barry said, then repeat with your white noise source ( asymmetric from poor input bias perhaps for CM range)  It also has a white noise PRSG source and FM sine log sweep.

Depending on duration of the noise sweep or sequence of a PRSG 98% of the time the RMS value of white noise is about 25% of the peak value.  while @Barry suggested Vpp=Vrms*3.5 or Vrms=28.5% 


which implies a longer capture time (1sec) with bigger peaks), so I still agree with him., but you only show a fastsweep