Some of the most popular Christmas toys including Road Rippers Lightning Rods and the I Am T-Pain musical microphone may hurt hearing, U.S. researchers say. Dr. Hamid Djalilian of the University of California, Irvine, and colleagues measured the noise levels of two dozen popular toys in stores and purchased the 10 loudest. Using a soundproof booth at UC Irvine Medical Center, the reseachers found all exceeded 90 decibels and several reached 100 or more -- equivalent to the noise of a chain saw, subway train or power mower. \"Generally, toys are safe if used properly,\" Djalilian said in a statement. \"We tested the sound levels at the speaker and again at 12 inches, which is about the length of a toddler\'s arm.\" However, if a noisy toy is held too close to the ears, problems could arise, Djalilian said. \"Children are very sensitive to loud and high-pitched sounds. Unfortunately, hearing loss from noise damage is permanent and not currently curable,\" Djalilian said. \"The louder a sound is, the less time it takes to cause hearing loss.\" Unprotected exposure to sounds above 85 decibels for a prolonged period can lead to hearing impairment, the American Academy of Otolaryngology said.