The Short Guide To Listening Vol. 8 - Low Pass Filter
Low Pass Filter - An EQ filter that allows the low frequencies to pass because it cuts the High end out of the track
High Pass Filter - An EQ filter that allows the high frequencies to pass because it reduces the low end out of the track
This article is some basic information for people that are getting started in live production, audio postproduction, and sound design.
If you were to talk to sound engineers, read articles, or watch Youtube tutorials about mixing music - You are sometimes told to use a High Pass filter on everything but the Kick or Kick Sub and the Bass Guitar. This might a good starting out, and it is one of those hard and fast rules to start to make the mix sound cleaner; this an excellent tip, so you're mixes to stop sounding to bassy or boomy.
Low Pass Filter in Live Sound
If you are a Front of House engineer or known as the sound guy at local events and are using a less expensive board, some of them do not have a lot of plugins or the ability to use more FX channels.
The board I use for live sound does not have a De-Esser (An Audio Plugin that takes out those harsh' S' sounds), and the microphones being used tend to be very bright. To reduce the higher frequencies harshness of people's voice and to try to remove those harsh "S" sounds, I'll use a low Pass Filter. Not only does it help with the harshness of those sounds; it makes the voice feel warmer and more full-bodied
Low Pass Filter In Audio Post
I love using both Low Pass & High Pass filters on most of my audio tracks or at least clips in my Pro Tools sessions sound editing for a project. It's fantastic to use these on background ambiances in a scene. If there is an external scene where two characters are speaking to each other in a forest, and you place some high-quality wind and cricket ambiance in the background. There is a big chance that the cricket within the ambiance will sound way too close and taking up valuable frequencies covering up some of the dialogue in the film. You can allow the dialogue to shine through while still putting the cricket in the distance by merely using a Low Pass filter. For ambiances, I like to start the low pass filter at around 5k Hz or even down to 1.5 k Hz. Are the two characters inside a house at night? You can drag that filter even lower to about 500 Hz. This will seem like the cricket is outside the home and not chirping inside.
Low Pass Filter is a very simple but great tool for you to use working on anything audio and very easy to test out and try for yourself!