Bought thru MO, don't remember having the receipt.
But anyway, the buzzing cound is kind of soft, so even the same charger judged by different people will have different option about it. Not to mention the surrounding noise level that u plug your charger.
So just giving a small suggestion here b4 u decide to call the MO guy:
If your charger still able to charge battaries and complete charging at the correct timing and temperature did goes too hot. I don't think you really need to charge the set.
OR
If you still find thye sound too much for u too feel safe, try borrow a set, maybe from anyone here that say the charger is slience, and try it yourself, just too prove that your ears are too POWERFUL.
Cos chances are, you're likely to get a set that behave the same. Hope this might lighten the stress on person who is in-charge of the MO. All this exchanging is no jokes, very stressful. :cry:
But like what I said if by anyway you feel uneasy, go check it out. Cos you pay to get a product you trust, and not to worry that you might ended up in flames middle of the night!