SMARTER EVERY DAY DIARIES:
Safe and Sound

Most of us have experienced moments of terror caused by an unexpected noise, be it a scream on a playground or footsteps in the middle of the night. Spotting a potential problem with our ears, not our eyes, is as old as mankind. Today this ancient instinct has a modern update—sensors that listen for the sounds of a cracked wheel to help keep trains from coming off their tracks. 

9 years ago