WEIRD noise from iMac speakers - Static?

So this is whats been happening all of a sudden overnight…

https://streamable.com/ya7ay

When I plug in my headphones and open iTunes, the headphone jack doesn’t work (Tried 2 different headphones) I played around with the sound settings - muting sound, microphone etc to no avail. This “static sound” comes from both speakers and comes on when the Mac plays a sound file (notification) iTunes or a website that has media files on it. When the notification or song finished, the noise continues for another 20 seconds before it turns of. When I play songs or divert the sound to a bluetooth speaker it works perfectly. I have done a NVRAM reset but didn’t do the job.

Morning guys, I sincerely appreciate your help! So I first did the SMC reset and during restart no static noise occurred when you hear the chimes when the Mac first starts up.

I then installed VLC and played a random song and although the static sounds now sounds more faint it still remains there. I then opened iTunes, same static sound, same level of static noise on both speakers..

It also appears in internet browsing, when there is a commercial thats playing or a sound file. It starts as the same time the notification or commercial does, then turns off 20 sec after.…..am starting to think it is the power board and socket?…. I have nothing else attached to the 6 plug power board except a lamp. I should try relocating the Mac to another room and try a different power socket?

I have put the iMac in the kitchen and plugged it in there, no static noise through the apple chime but as soon as I open iTunes, a website or a notification comes on so does the static noise, however it seems more faded. the intensity of the noise seems to vary. I believe it might be an issue on the logic board. I attempted to log out and log into a guest account to see if its a software issue however it does the same thing. frustrating! If I knew where on the logic board the problem is located I would take it apart and inspect it.