Under heavy load, CPU produces noise.
Under heavy load, CPU produces noise.
You're likely dealing with a pump inside the CPU area. Try listening near the fans for any unusual sounds. Check how the power supply fan operates.
Great observation! Could be an overheating pump or debris in the fans. @Ayush007: Including HWMonitor images with CPU, GPU temps and fan speeds would be really useful.
I gave it a shot, but I'm still puzzled. My original PC case has a low PSU, making it hard to say for sure. However, the case cooler fan seems to be working fine.