I honestly don't know, but some chargers (and other things) make whistling noises. For example, my HP laptop power supply makes that kind of whistling. So does my cheap phone charger. Never had a problem with them. My monitor makes a quiet humming noise when the screen brightness is near the middle...

I just got a new Raspberry Pi 3 Model B, with a generic 5V/2A adapter Everytime I plug it in, the adapter makes a whistling sound. I only connect an ethernet cable to it, using SSH to login. The sound stops when I shut down the Pi using sudo halt -h Is this a broken adapter? Or is it OK? Will it bre...