Selective hearing

Filling your ears with music from noise-blocking earphones doesn’t just diminish outside noises, but also reduces the ability to hear things you might want to, like traffic noise when you cross a street, reports the New York Times. To reduce this nuisance of taking the earphones in and out of your ears, Shure is packaging a push-to-hear switch with its E500 earphones, which cut ambient noise by 30 to 37 decibels. Press it, and the music in the headphone mutes, while an external microphone picks up ambient sounds.

Riot control

US researchers are working on a new non-lethal weapon that could quite literally bring rioters to their knees ? by sliming them, according to the New Scientist. Riot police would wear a back pack with three cylinders ? one containing compressed air, another filled with plain water and a third containing very dry, finely ground, polyacrylamide powder. A nozzle would spray these in the direction of a mob. As the two jets mix in the air, they create a slimy mixture that covers the ground and causes everyone in the area to fall down.