This gem comes courtesy of ResourceShelf (Gary Price is one of my personal heroes--when I used to work here he and Tara Calishain were like mentors, unbeknownst to them I am sure).
Of the 22 toys the Sight and Hearing Association tested this holiday season, 5 were louder than a chainsaw. (As an aside, I will say that anyone who purchases a toy called the "Light & Sound Weed Trimmer" for their child deserves what they get at 100 decibels.)
The article goes on to explain how much exposure to such a noise can lead to hearing loss. Myself, I don't really need to know. "Louder than a chainsaw" is a sufficient descriptor. The prospect of long term hearing loss is less daunting than the more immediate possibility of me seizing the toy and performing some sort of jailable offense with the it and perhaps the child as well.