Loud power steering pump

When driving my 2008 Jimny, there's a loud droning noise that sounds like it's coming from the engine bay where the power steering pump is, it gets louder at higher speeds/

Has anyone had any experience with fixing this/ is it fixable? Or will I need to invest in some sound deadening 

Assuming it is the power steering pump, try replacing the fluid as the first step.

inspecting the fluid should tell you a bit as well. turn the wheel a few times side to side full over. the fluid should be almost  clear and not milky, hazy or foam and no particles or too much bubbles..

I had a pump fail on a vw and I went thru most of the above.

Most pump fails will make the pump make more noise when turning.the wheel or you will feel less power from it on the steering wheel.

to listen more presice you could use a piece of broom stick or similar piece of wood to transport and isolate the sound from the part you suspect and up to your ear. or just buy a car stethoscope.

When does it make the noise-

All the time the engine is running, moving or not, in neutral and in gear (both when moving and stationary)?

Only when the car is moving?

When stationary, all the time?

When stationary, only when the gearbox is in neutral, stops when it is in gear? (with the clutch full down obviously).

If the answer is "absolutely all the time, neutral or in gear, moving or stationary" and it sounds like it is coming from the power steering pump, slacken the idler pulley and take the power steering belt off.  If the noise goes it is either the power steering pump or the idler.

Gearbox has not been rebuilt (yet...) but seems to be running fine albeit a whine in 4th.

I'm assuming I can drive the car to test and see if the noise goes away?