Are you really talking about the brand new Surface Laptop 4? Does the new Surface Laptop 4 have the exactly same issue as Surface Laptop 3?
Yes, the description in this thread seems to match what I've experienced. There's a sound that seems electric rather than mechanical in the SL4 that appears to come from the back edge of the keyboard. It appears to have a bit of a pattern to it, not a constant buzz. I've found that if I hold down a key such as page up or page down, the sound stops, then starts again as soon as I let go. CPU load is ~1%, pretty much idle.
It's not loud. It's just on the edge of my hearing, just enough to be annoying in a quiet room. The fans are silent unless the system is under load.