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How Loud is Too Loud? Video
Scientists measure the loudness of sounds in units called "bells", named after the inventor of the telephone, Alexander Graham Bell. Talking softly is about 30 decibels. Speaking in a normal way is about 60 decibels. But an airplane, a boom box, or a rock concert can be 100 to 140 decibels, and that is loud enough to cause a permanent hearing loss.