Audio Effects: Filters

Filters affect the timbre or frequency content of a sound. As a point of reference to the examples, here is the clean recording:

Low pass filter (LPF)

An LPF removes frequencies above a cutoff point.

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The clean recording going through an LPF with the cutoff set to 1KHz

 

High pass filter (HPF)

Removes frequencies below a cutoff point.

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The clean recording going through an HPF with the cutoff set to 1KHz

 

Band pass filter (BPF)

A BPF removes frequencies above and below a certain range. A BPF can also be defined as using an LPF and an HPF simultaneously.

 

Notch filter

A notch filter emoves a specific frequency or range of frequencies. This is the opposite of what a BPF does.

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The clean recording going through an notch filter at 200Hz and succeeding octaves

 

Equalization

Most of you will understandably be unfamiliar with the above filter shapes. However, I am sure that just about everyone has encountered equalization. They are also included in this group of effects. Equalization (EQ) is the increase or reduction of various frequencies in a signal. There are two commonly used types of equalization

Graphic EQ

Provides separate controls for specific frequencies across a given spectrum.

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The clean recording going through a 10 band graphic EQ for added brightness (decrease in lower and increase in upper midrange and high frequencies)

Parametric EQ

A single control (knob or slider) on a parametric EQ, on the other hand, is able to control a range of frequencies. The center of this range is the frequency that is affected the most by the controller. The amount of change then decreases the further the frequency is from the center. While not as precise as a graphic EQ, it’s more intuitive and effective for broad and quick changes.

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The clean recording going through a parametric EQ for an old radio sound effect

 

Filter effects actually abound, and perhaps we can cover more of them later. But for now, these are among the ones you will find most useful.

And… that’s all I want to cover regarding audio effects! We’ll undoubtedly get into this some more. But for now, I’d like everybody to take the time to explore them in your respective DAWs.

Good luck and have fun!