To make fans work quietly,manufacturers use slow-runningmotors to spin the blades. Thisreduces noise but also reducespower, producing weak airflow. To make powerful fans, theyuse fast motors to spin the blades.But fast motors create more noise.Powerful and quiet is very difficultto achieve in a conventional fan. The new Dyson Cool fans have beenengineered to be quieter, use less energy- yet generate powerful airflow.