Ben recently made me aware of this article about earplugs that protect the hearing of soldiers:
British troops getting ready to deploy to Afghanistan are being issued with electronic sound-cancelling earplugs designed to let them hear what they need to — orders, conversations, enemy footfalls — but prevent hearing damage caused by explosions, gunfire and so on.
Science fiction author Larry Niven predicted this technology in 1975. From his story “The Borderland of Sol”:
“Earplugs,” said Ausfaller, holding up a handful of soft plastic cylinders.
We inserted them. Ausfaller said, “Can you hear me?”
“Sure.” “Yah.” They didn’t block our hearing at all.
“Transmitter and hearing aid with sonic padding between. If you are blasted with sound, as by an explosion or a sonic stunner, the hearing aid will stop transmitting. If you go suddenly deaf, you will know you are under attack.”
The real-world earplugs are slightly better than Niven’s; instead of cutting off all sound, they can simply reduce it to a safe level. (So you can hear the explosion without suffering hearing damage from it.) But apart from that detail, Niven’s description was spot on.