Started randomly, got a little louder as the week continued. Sounds like a power steering pump whining mixed with timing chain rattle.

No loss of power- seems to be RPM dependent, too. Just an awful noise thats constant so long as the engine is on

Its an auto 99 I30 with 154k on it

Any input would be helpful. I think the previous owner ( a "mechanic") said he replaced the timing chain - that'd have been before my brother bought it 20k miles ago.

Maybe..bad pulley bearing. When was the last time you replaced the belts?

I have personally done nothing to the car besides brakes and oil. I know the alternator was done, water pump too.

Check the idler pulley. It could possibly be the bearings going bad in the pulley. That would be my first guess.. by what I could hear in the video.

^^ Agreed. On my 98 I had a problem with my alternator bearing being bad, idler pulley, and ac clutch. Got a new alternator and AC clutch plate and bearing, and I was golden. Idler pulley wasn't really loud given that it's the smallest.

easiest way to do things is remove the accessory belt and start the engine, that way you can verify if its something like the AC compressor or alternator, or if its the timing chain.

if the noise goes away when you start the car without the accessory belt, you know its one of the accessories. get a mechanics stethoscope and with the car running, put it on all your accessories like the alt and power steering pump and see where the noise is coming from. also when the belt is off, spin the pulleys by hand and see if one is tensed up or spins rough

If the noise goes away when you turn on the AC then you will know for sure it is your AC compressor pulley/clutch. Happened to my 96.

+1 on the idler pulley