Strange grinding/whirring sound coming from iMac 21.5″

Over the past month my iMac 21.5" has produced a constant grinding sound whenever it is powered on.

I took it in for repairs to have its hard drive replaced, which was the initial assumed cause of the noise. With a new SSD installed, the exact noise remains. The interior of the machine/fan was thoroughly cleaned at this time.

I took the computer back in to check if the fan was broken instead, but the fan was determined to not be the cause either. At this time, the computer was rotated around to dislodge any potential loose material inside.

Both times when I took my computer into the repair shop the grinding sound seemed to stop/was less noticeable. The only difference in my computer's setup in the shop was a different main power cable, and it was also booted from the shop's own external hard drive. I have had my computer set up in two separate living spaces in the span of this last month, and in both spaces the noise remained. I have tried maneuvering the computer to dislodge any loose material inside with no luck.

The computer's functionality/cooling/diagnostics are otherwise fine. Could any type of software cause this? Anybody have any idea about what this could be?

Attached is an audio example of the sound: Grinding noise