That loud toy under the Christmas tree might do more than drive parents crazy. Researchers at UC Irvine have found that some children's toys, if held close enough, can reach decibel levels similar to a subway train or a chain saw. Researchers suggest buying toys with speakers on the bottom and testing them in the store to see if they're painful to the ear. For noisy, must-have toys already under the tree, they recommend supervision and putting tape over the speakers to lessen the sound.