BFR sound files.

[Infernus]

In your planetside directory open the Patch 3 folder... there should be a sound file called 'Patch3', it contains all of what sounds to be the BFR sounds...

[Spee]

Argh Theres A Lockdown Sound File In There, Noooooooos!!!11

[MrPaul]

Argh Theres A Lockdown Sound File In There, Noooooooos!!!11
Let's hope to God that that is to do with the VS wings locking into position, rather than a giant TR anchor systam.

[Roswell34]

damn, I cant see them
Because i have left PS last month so i didnt dl the patches

[Sokko]

Um... sorry to break it to you, but patch3.wav contains nothing but Capitol Dome, Deliverer Variant, Earthquake, and Meteor sound effects, and those last two were the most recently added things. If you doubt me, see for yourself: patch3.idx contains a listing of all sounds in patch3.wav, and there's not even a hint of anything sounding remotely like BFRs in there. Aside from the earthquakes and meteors, everything in that file has been there since the Deliverer Variant patch.

EDIT: It also contains the modified TR lockdown noises to go with the faster animations and lockdown time they were given. That might account for the "locking down" noise you hear.