Gearbox nose

An often overlooked aspect of a clutch is it doesn't just connect the drive on the gear box.
It's applying pressure on the flywheel and therefore the crankshaft.
Worn thrust bearings on the crankshaft can make the crank actually move along it's axis.
so you applying the clutch actually "MOVES" the flywheel in towards the engine.
So I'd remove the alternator drive belt and push/pull crankshaft pully in/out .
Your checking for crankshaft longitudinal play,
can the crank be pulled/pushed in out of the engine.
And while the belt is off start it up,
now your checking for the noise to be from a faulty aspect of the drive belt system.
If the noise is gone it could have come from any drive pully.
or from a failed crankshaft pully.
Many are constructed from steel/rubber and can fail.
de/laminate.
and this can make some very strange noises.
Take the belt off.

G/box layshaft bearings ? , though not usually a " whoop whoop " noise .

I actually had one in not long ago with layshaft bearing failure.
And the best way to describe the noise was like a ratchet on some ancient farm mechanical device that hadn't seen lube for years.
Honestly it made my blood run cold.