Do you ever want to make those annoying kids just go someplace else? Well, now you can : The device, called the Mosquito (”It’s small and annoying,” Mr. Stapleton said), emits a high-frequency pulsing sound that, he says, can be heard by most people younger than 20 and almost no one older than 30. The sound is designed to so irritate young people that after several minutes, they cannot stand it and go away. By way of demonstration, he emitted a batlike squeak that was indeed bothersome.