This link points to a measurement of the frequency noise at the 40m.

'MC_F' means the feedback to the VCO used to keep the MC locked. Below ~100 Hz, there is also feedback to the MC length and so you cannot assume its frequency noise.

From 100-1000 Hz its all acoustic pickup on the PSL table. Above 1 kHz, I believe its all VCO phase noise.

I also suggest that from now we all decide to post the actual data along with the plots we post here. Also the .m matlab file which generates the plot as done at GEO. This makes it much easier to reproduce the result a year down the line.