Do I need a new PSU or psu cable ?

Are you referring to the power cable from the outlet or a cable inside the system?

Yes

the kettle plug coming out of the power supply

nothing to do with the thing inside.

The only reason a psu might buzz is if something is contacting the cooling fan.

I might consider replacing the unit, particularly if it is a poor quality brand.
A failed psu can damage anything it is connected to.

If it's oxydized then replace the power cable (if the buzzing occurs at the connection) or replace the whole PSU.

what is oxidised ?

It makes the sound of when you haven't plugged something in properly and you hear crackling

except I have checked and it is plugged in properly



So should I just but a new PSU kettle plug ?

Crackling implies a bad connection. If it crackles at the PSU connection, then visually inspect the connectors. If they are not the normal color, then replace the power cord and the PSU if it also is discolored (usually brownish caused by sparks).

actually it crackles at a point in the wire

By that I mean, If it is crackling, If I just move the wire left or right and I can stop the crackles

Replace it ASAP.

the wire or the psu ?

The power cord and make sure you use one that's rated for your PSU. Replace the PSU only if the connector is damaged.

A power cord is cheap, they are standard.
Try using one from somewhere else, like your monitor.
If you still hear the noises, replace the psu.
If a different cord fixes the problem, then OK.

What brand and model is the PSU?
Some are so bad that you should replace them regardless.