Buzzing low pitch noise near PSU area - electrical terminal arcing?

There is a constant buzzing/higher pitched noise coming from the second gril (counting from bottom up). It reminds me of an arcing terminal (which due to poor connection sometimes happens inside electrical outlets for example).

The buzzing is noticeable when the machine is idle.

Does anyone else have this sound when the device is idle? The dBm is around 72 at the closest point near gril area, so its not excactly silent.