What is a reflection filter?
The reflection (also known as pop shield or pop screen) filter is the type of product whose purpose is to provide some helpful absorption of sounds that would otherwise reach the rear-facing sides of the mic. Also, it catches and absorbs some of the direct sounds from the vocalist. The latter helps to minimize the amount of energy that gets out into the room in the first place, thus reducing the amount that subsequently bounces around to get back into the mic.
A typical pop filter has one or more layers of acoustically semi-transparent material such as woven nylon stretched over a circular frame and often includes a clamp and an adjustable mounting bracket. Metal pop filters use a fine mesh metal screen in place of the nylon. Some studio condenser microphones have an integral pop filter built into their design.
An improvised pop shield, functionally identical to the professional units, can also consist of material from tights or stockings stretched over a kitchen sieve, embroidery hoop or a loop of wire such as a bent clothes hanger. It is crucial that you do not attach the pop shield directly to the microphone. Vibrations will be transmitted from the shield to the mic.
Popping sounds occur mainly in the pronunciation of aspirated plosives (such as the first ‘p’ in the English word “popping”). Pop filters attenuate the energy of the plosive. It otherwise might exceed the design input capacity of the microphone, leading to clipping. In effect, the strands of the filter material intercept and brake the discrete plosive envelope of sound energy 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 people use de-essing. Whereas most products use a simple acoustic foam panel, companies like the SE design uses clever multi‑layer panel construction. Its design extends the LF performance without making the unit excessively heavy or thicker.
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 utilized by vocalists on stage to reduce plosives and saliva. However, they may not be as acoustically transparent as a studio pop filter. The differences between the various alternative filter designs come down to the usual compromises of size, weight, cost and the efficiency of their low‑frequency absorption. Bigger is generally better, as is thicker (both lower the LF‑absorption frequency roll-off).