White noise (periodically) when recording sound

FIrst time here - is this the right forum for Sony Movie Studio Platinum 13?? I'm not sure??

Wow - I am really upset as lately I have been having what I call, "white noise" when recording in Sony Movie Studio Platinum 13.

I never had this happen before but now - sometimes - I get this low hum or white noise or static sound especially evident during pauses. It's baffling as I never had it before.

Does it even matter? Maybe it will not be noticeable when speaking? I don't think it is so maybe I should not worry?

I did some reasearch and I know people say it can be like 100 different things. Interference from other electrical appliances RFI, EMI - I prob got those terms wrong but something like that. 

To me, it seems to be picking up the low hum of the fan in my computer. I am using the AT2020 USB so of course it plugs into the computer usb port. 

Other times, the sound is perfect and there is no static or white noise during brief pauses in speaking. 

I tried shutting off all appliances, well except the computer modem - which actually sits close to where my computer is - maybe I should move it farther away. I prob need to have it running when in Movie Studio I would think.

From the background research I see where people are saying it took them weeks to figure it out, tried all different things.

I can try grounding wire. Someone said to hook up a wire to the computer and ground it. Haven't tried that yet.

I didn't see anything under noise reduction in Sony Movie Studio Platinum 13 so I dont' think it has that feature. 

I see there are also plugins like ISOTOPE although that looks quite expensive.

I remembered I do have Sony Soundforge - though I never used it. However, I fired it up and saw where there is a method to suppress background noise but so far it hasn't worked. Maybe I need to play w the settings more. 

This is frustrating as I am on the verge of finishing my long worked on project.

I guess I"ll try messing w Sound forge some more, moving he modem further away, shutting off all other electrical devices/unplugging them, turning off bluetooth devices - I even turned off the refrigerator, hooking up a grounding wire (I know I read that somewhere) etc.

Any other tips will be appreciated!