The power brick on my thinkpad is making a fizzing/buzzing noise, almost like a highly carbonated drink, just a little more muted. It's still working fine and giving a charge. Is it likely there's something wrong with it? It just started today, I think (though I hadn't checked in the past)
Make sure the line cord is firmly seated into the brick.
Try a different power outlet.
Test a different adapter, if you have one available, just to be sure.
If those don't work, and if the machine is under warranty, just call Lenovo and tell them the adapter is audibly making noise, and that you've tested it in multiple locations, the machine works fine otherwise, and the noise is certainly coming from the adapter. They should ship you a replacement with no trouble - make sure to keep the line cord because they only ship the brick piece. (The odds of the line cord being defective, especially with a noise, is basically nil.) Make sure you have the machine model type and serial number available immediately when you call. (These are on the same black-and-white sticker on the bottom of the machine, TYPE: and S/N:)
If it's not under warranty, you should buy another. The odds of it actually damaging the machine are slim-to-none but it will probably just quit working soon enough and will also probably start to overheat, so there is a fire hazard involved.
Sounds like one of the capacitors is going. Usually gives crackling sound. That or sometimes when a transformer insulation starts to break down - begins to sizzle. Either way, sounds like you may need to get a new adapter.