PC Noise Issue

Here’s a video. that sound comes in bursts - every 5 or so seconds. sometimes longer sometimes shorter and sometimes stops altogether for several minutes

the same sound occurred on my old pc too. i’m not sure if it’s a fan down there or an issue with the actual psu.

it’s been making that noise for several months now, honestly from when i purchased it. happened with my old pc too so not sure if it's normal or ..?

if anyone could give me more information, it would be much appreciated