Mastering Sound Quality: A Quick Guide to Audio Equalization

April 8, 2022
3 mins read

Being able to capture good-quality sound is a crucial step in filmmaking. It’s essential to capture location sound and room tone with good levels, as they form the foundation of good-quality sound in your film project. Post-production editing will be more challenging if you pick up very low-quality sounds. There’s only so much fixing you can do! Using equalization in post-production editing and understanding how it works will aid the editing process and help you be aware when recording sounds during a shoot.

What is Equalization?

Equalization, or EQ, is the process of adjusting the balance of frequencies in an audio signal. EQ is used to correct imbalances in the frequency spectrum and create the desired tonal effect. Adjusting the equalization of a recorded sound is usually done using an equaliser on a Digital Audio Workstation. The equaliser tool allows you to cut or boost specific frequency bands, which can help shape any sound’s tonal character or make it more suitable for a particular scenario.

Reading an Equalizer

On your chosen DAW, there will be a tool called an Equalizer. This is used to edit the frequencies of any audio. The equaliser will be in the form of a graph, with the x-axis denoting the frequency range (Hz) and the y-axis denoting the decibels (dB). Across the frequency range on the x-axis, there will be certain frequency zones. These can be adjusted using EQ points (usually shown by a number). The lower the number, the lower the frequency zone.

A graphical equaliser is what we call a Parametric EQ. This offers continuous control over every parameter. Parametric EQs are always a good option due to their flexibility and versatility. Here’s an example picture of a parametric EQ.

EQ example in logic - audio equalisation

EQ for removing unwanted sound

Noise can be found in an array of recording scenarios. If you’re a foley artist, eliminating noise is a must, as it can ruin the effect of the sound you want to create, such as footsteps. That noise sounds like a hissing sound and is present in the higher frequency spectrum. Alternatively, you can get a rumbling sound that falls on the frequency band’s lower end. We can use EQ to eliminate these certain noises.

All equalisers have settings called a high pass and low pass filters. A high pass filter allows only the higher frequencies to pass through, cutting off the low frequencies. This would be used to eliminate rumble. A low pass filter does the opposite, letting only the low frequencies pass and cutting away the higher frequencies. This would be used to get rid of any hiss.

It’s also essential to note the different shapes you can get for the EQ points. The shape will always be a shelf when using a high or low pass filter. This will allow the user to cut away frequencies.

EQ for Shaping Sound

While an everyday use for an equaliser is to eliminate unwanted frequencies, we can also shape the sound by enhancing specific frequencies. As we mentioned the shelf shape above, there is also a notch option. This is used when editing narrower frequency bands.

You can use notches to boost specific frequencies across the entire frequency spectrum. This can be done in the middle area of the frequency spectrum, where there are specific tones that you may want to bring forward. You can also use notches to dip at certain frequencies to reduce or even cut them out entirely. This can be an excellent tool for shaping sound and highlighting certain tones for better audio results.

EQ example - audio equalisation

Equalization and Dialogue

Using an equaliser will almost always be necessary when recording dialogue, whether for a podcast, voiceover or ADR. Having high-quality sounding dialogue can elevate your projects, resulting in crystal clear dialogue. However, some issues can arise from recording dialogue. One is room resonance. When any sound is produced, different rooms will build up certain frequencies more than others, which can, in turn, imbalance your dialogue recording. While you want only to capture the sound of someone’s voice, the sound of the room can be picked up.

Here’s a video from In The Mix with an in-depth tutorial on how to make your dialogue sound better. This video showcases audio editing in a precise manner. He breaks down each EQ zone and shows how to adjust certain frequency bands accordingly.

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Zoe Sones

Zoe Sones is a UK-based composer who focuses on acoustic contemporary classical and ambient electronic composition. In her works, she explores an array of textures and timbres of both instruments and nature’s very own sounds. She enjoys creating haunting electronic drones, writing harmonically rich and serene chords, while also being a bedroom DJ.