AC Charger makes a high pitch sound when connected, Is this normal?

[OceanView]

I noticed a high pitch sound coming from the AC charger when connected.
The sound is faint so you can only hear it when there is no other sound in the area.

Is this normal or do I just have a bad charger?

 

[B. Diddy]

The charger for my Acer A100 does that only when it isn't actively charging the device. So I hear a buzzing when it's plugged into the wall but not connected to the tablet, or when the tablet is fully charged but still connected to the charger. I don't think it's a bad sign.

 

[D-Caf]

It's "probably" ok, but if it's annoying I would see if you can take it to a Barnes and Noble and get it swapped out. I have not carefully listened to my charger, but I've never noticed any high pitched sound from it (that or my hearing is just shot). Generally in electronics if there is a sound from it is either: badly designed/constructed, old and warn out, or the outlet it's plugged into is providing voltage/current out of spec or badly grounded.