Frequency Ranges and Equalization
The entire range of human hearing, from 20 Hz to 20,000 Hz, can be broken into a
spectrum of frequency bands: low, midrange, and high.
Note: Different devices define these ranges differently; the following ranges
are approximate.
Low (20–250 Hz)
Audible bass frequencies start around 20 Hz, though many speakers cannot reproduce
frequencies this low. This is an example of how audio meters can be deceiving, because
the meters may show very high signals but the speakers are not capable of making
sounds that low. The lowest frequencies are felt as well as heard, and require the most
power to amplify. Often, subwoofer speakers are used just to handle the low
frequencies in the mix (the 0.1 channel in a 5.1-channel surround sound mix is a
dedicated low-frequency effects channel).
If you are trying to increase the impact of sounds like kick drums or explosions, add
gain around 30 Hz or so. Filtering out 60–80 Hz removes a lot of low-end noise and
rumble from wind or microphone handling. Between 150 and 250 Hz, you can add
“warmth” to the audio signal (or subtract it).
Midrange (250–4000 Hz)
Humans are most sensitive to this part of the audio spectrum. Most of the frequencies
that make speech intelligible are in this range. You can make audio tracks stand out
more in the mix by subtly increasing the frequencies in this range. At the top of this
range, around 4 kHz, is where vocal sibilance occurs. Too much sibilance can be grating,
but a little bit can make the voice sound crisp and detailed. If your track has too much
sibilance, try reducing the 4 kHz range.
High (4000–20,000 Hz)
The high end of the frequency spectrum adds “brightness” or “brilliance” to a mix, but
no longer affects factors such as impact (bass) or speech intelligibility. High-end
frequencies can be grating, so don’t boost these frequencies too much.
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Part I
Audio Mixing