You have probably seen pictures of your favorite band recording vocal tracks in the studio and you have probably noticed a pop filter in front of the microphone that the singer was using to record the vocal track with. The reason that pop filters are used are basically for control over the source of the audio that is being recorded.
A microphone, just about any microphone, has a diaphragm mounted inside of it. This diaphragm is connected to a coil of wire and is mounted inside of the head section of the microphone. When you record any kind of sound with a microphone it causes this diaphragm to vibrate. When the diaphragm inside of the microphone vibrates due to changes in air pressure it creates an electrical signal as the coil of wire connected to the diaphragm vibrates back and forth inside a magnetic field. These electrical impulse are transferred down the microphone cable and received by your recording equipment in order to capture the sounds produced by the source. The source can be a voice, a guitar amplifier or any other source of sound pressure.
If these impulses are greater than the ability of the microphones impulse range to produce they will cause a popping sound and result in very poor audio capture. The diaphragm in a microphone is much like a very small speaker in reverse. Instead of producing sound like a speaker would the diaphragm is a passive form of a speaker that produces electrical impulses to be recorded as a sound. Just like a speaker a microphone has a certain range it can operate in and if the sound pressure is greater than the range it can accept then undesirable effects will be present in the audio recording. This is where a pop filter comes into play.
A pop filter will reduce the highest sound pressure instances such as when a singer pronounces the letter “P” in a vocal track. This sound produces a much higher amount of sound pressure than most other sounds that are normally heard and must be reduced to nominal levels in order to be able to record a certain range of sound on a scale of decibels that the diaphragm can accept without causing undesirable effects. When this “P” sound is vocalized it causes the diaphragm to slam into the mount or it can cause the coil to bottom out in the electrical magnetic field that it uses to produce the electrical impulses. When this happens in real time a pop filter can reduce this effect while remaining transparent to the other impulses that it will receive during a recording session. These pop filters are made of materials that are light and flexible and that can allow certain types of sounds to pass without interruption and reduce those sounds that will cause a “pop” in the diaphragm of the microphone.
You might have seen several different types of pop filters that are normally used in video and audio recordings. Some are simple foam caps that are placed over the head of the microphone while others might be mounted a short distance away from the microphone being used to capture the sound. In all cases the pop filter will reduce unwanted effects while retaining as much of the source material as possible. It is always recommended that you use some form of pop filter because if not the unwanted effects can not be repaired later in post production with compressors or an equalizer. The source of your audio material should be of the highest quality during the initial capture of the sounds in order to produce the finest end product for your listeners.
Pop filters are relatively inexpensive and can provide years of service for your studio. Some studios may even hand make pop filters for specific use in certain environments that may have windy conditions or a high level of background noise that needs to be filtered out during a recording session.