The Audio Frequency Spectrum

The range of human hearing generally spans from 20 Hertz (abbreviated Hz) up to 20,000 Hertz, and represents the main spectral focus of audio engineering. This is like the canvas that musicians, sound designers, and audio professionals use to express their art.

Have you ever looking at an image, and would describe it as "busy" or "a lot going on"? Just as our brains can be bogged down by too much visual information, it can also be overstimulated in the audio range. It's one of the goals of mixing a song, to place the different instruments and sounds in their best place, like paint on a canvas, so they don't overstep each other, or overstimulate the listener.

This frequency span can broadly be broken down into three categories: Bass (20-250 Hz), Mids (midrange, 250 Hz to 4 kHz), and Highs (also known as Treble, 4-20 kHz and above). When digging into the details, it's more helpful to segment these even further:

Sub-Bass

20-60 Hz

The lowest portion of the spectrum, where the sound is almost felt more than heard - very important in dance/club music. Your Bass instruments and kick drum should be present here, but not overly built up.

Bass

60-250 Hz

This is typically where the Bass and Rhythm section are focused, but plenty of other instruments, like piano and guitars, can creep down here as well.

Low-Midrange

250-500 Hz

Entering the mid-range, you are likely to find many instruments coming into the picture, especially around their fundamental frequency. That means this region is the start of a larger balancing act; ensuring there's room for all the instruments in the mix.

Midrange

500 Hz - 2 kHz

We're solidly leaving the low end area here, and where, while our balancing dance continues. Keeping the clarity of different instruments is very important here, so their not dancing on each others tones.

Upper-Midrange

2-4 kHz

This region tends to be where vocals are, and room often needs to be made to ensure they have a place to land. This also means that all the harsh parts of vocals can build up in this region, like sibilance and plosives. Human hearing is most sensitive in the 2-5 kHz range, so we can be more sensitive to the subtleties of this region.

Presence

4-6 kHz

This region can make the listener feel closer or further away, depending if it has been boosted or cut. Cymbals tend to inhabit this range, as well as overtones from other instruments in the mix.

Brilliance

6-20 kHz

This region tends to have a lot of the harmonics, so light boosting this region can lead to a pleasing, polished effect. Cutting this region can have the opposite effect, and make the sound feel warmer and more distant.

Training Your Ears

You might find some diagrams and charts that show you what frequent range an instrument is known for, but one should not rely as these as much as their own ears. A lot can affect an instruments sound, such as how and where it was recorded!

A really useful thing you can do in your DAW, is to set up some plugins to be able to solo these individual regions. Something like FabFilters Pro-MB multi-band compressor can allow you to mark out these frequency ranges and solo/preview each. If you don't have "one plugin" that can do this, you can also set up multiple stock EQs plugins with high/low pass filters to carve out the region appropriately, and toggle them on/off accordingly.

Making EQ changes to tracks while soloing regions on the master bus can really make the changes pop, leading to less heavy-handed edits. This trick also works well if you have a DAW project of reference tracks loaded, so you can hear how they were mixed in those regions.