A pop filter or pop shield is a noise protection filter for microphones, typically used in a recording studio. It serves to reduce or eliminate 'popping' sounds caused by the mechanical impact of fast-moving air on the microphone during recorded speech and singing. It also keeps moisture off the microphone, which can cause mold growth. Additionally, a pop filter can protect against the accumulation of saliva on the microphone element. Salts in human saliva are corrosive; therefore, use of a pop filter may improve the lifespan of the microphone.
A typical pop filter is composed of one or more layers of acoustically semi-transparent material such as woven nylon stretched over a circular frame, and often includes a clamp and a flexible mounting bracket. Metal pop filters use a fine mesh metal screen in place of the nylon. An improvised pop shield, functionally identical to the professional units, can be made with material from tights or stockings stretched over a kitchen sieve, embroidery hoop or a loop of wire such as a bent coat hanger. It is important that the pop shield not be attached directly to the microphone as vibrations will be transmitted from the shield to the mic.
Popping sounds occur particularly in the pronunciation of aspirated plosives (such as the first 'p' in the English word "popping"). Pop filters are designed to attenuate the energy of the plosive, which otherwise might exceed the design input capacity of the microphone, leading to clipping. In effect, the plosive's discrete envelope of sound energy is intercepted and broken up by the strands of the filter material before it can impinge on, and momentarily distort, the sensitive diaphragm of the microphone. Pop filters do not appreciably affect hissing sounds or sibilance, for which de-essing is used.
A pop filter differs from a microphone windscreen. Pop filters are generally used in a studio environment, while windscreens are typically used outdoors. Windscreens are also used by vocalists on stage to reduce plosives and saliva, though they may not be as acoustically transparent as a studio pop filter.
Some studio condenser microphones have an integral pop filter built into their design.