Diagnosis
That’s coil whine. It’s not super common, but it happens with some electronics. It’s caused by electrical components (like inductors or capacitors) vibrating at a high frequency under load. It’s generally not a sign of imminent failure, but it can be annoying.
How to Fix It
First, identify which point it is. Unplug them one at a time until the noise stops. For the noisy unit, try plugging it into a different outlet, preferably on a different circuit if you can. Sometimes poor or “dirty” power from the wall can exacerbate coil whine. If changing outlets doesn’t help, the internal power supply in that specific unit is likely the source.
If That Didn't Work
If the noise is persistent and bothersome, and you’ve ruled out the outlet, the unit itself has a minor manufacturing variance. Since this can be subjective but is a physical characteristic, your best bet is to contact Google support within your warranty period. They are typically aware of this issue and should be able to process a replacement for the affected point.
Heads Up
The noise might change or become more noticeable when the network is under heavy load (like a big file transfer or multiple 4K streams). It’s a physical vibration, so if the unit is on a hard surface like a wooden shelf, it might resonate more. Putting a soft pad or cloth underneath it can sometimes dampen the sound.