A device placed in front of or around a microphone to shield the mic element from wind. Wind screens are generally made of foam, or a foam-like material – something porous. The idea is for the device to allow sound to pass through without interference, but to limit larger pressure variations such as those caused by wind. Mic elements are necessarily sensitive to extremely small changes in air so they can pick up sound properly. Wind is interpreted by a microphone as a very, very large change in pressure – far beyond what it is designed to handle – thereby causing distortion either due to the element moving in a non-linear fashion and/or because the electronics driven by the output of the element distort. The result is a very unpleasant sound. When operating a microphone in windy conditions it is usually a good idea to employ a wind screen. Many professional microphones have wind screens made specifically for them and their shape, but it is not uncommon to use generic wind screens in some applications.