Author Topic: Audio Spectrum Explained  (Read 4846 times)

Offline Rotten Johnny

Audio Spectrum Explained
« on: December 28, 2012, 09:22:43 AM »
Found a handy reference explaining the audio spectrum so figured I'd repeat it here.  All credit to Teach Me Audio.

The audio spectrum is the audible frequency range at which humans can hear. The range spans from 20Hz to 20,000Hz and can be effectively broken down into seven different frequency bands, with each having a different impact on the total sound.

The seven frequency bands are:

Sub-bass > Bass > Low midrange > Midrange >Upper midrange > Presence > Brilliance

Sub Bass: 20 to 60 Hz

The 'sub bass' provides the first usable low frequencies on most recordings. The deep bass produced in this range is usually felt more than it is heard, providing a sense of power. Many instruments struggle to enter this frequency range, with the exception of a few bass heavy instruments, such as the bass guitar which has a lowest achievable pitch of 41 Hz. It is difficult to hear any sound at low volume level around the 'sub bass' range because of the Fletcher Munson curves.

It is recommended that no or very little boost is applied to this region without the use of very high quality monitor speakers.

Too much boost in the sub-bass range can make the sound 'too powerful', whereas too much cut will weaken and thin out the sound.

Bass: 60 to 250 Hz

The 'bass' range determines how fat or thin the sound is. The fundamental notes of rhythm are centred on this area. Most bass signals in modern music tracks lie around the 90-200Hz area. The frequencies around 250 Hz can add a feeling of warmth to the bass without loss of definition.

Too much boost in the 'bass' region tends to make the music sound boomy.

Low Midrange: 250 to 500 Hz

The 'low midrange' contains the low order harmonics of most instruments and is generally viewed as the bass presence range. Boosting a signal around 300 Hz adds clarity to the bass and lower-stringed instruments. Too much boost around 500 Hz can make higher-frequency instruments sound muffled.

Beware that many songs can sound muddy due to excess energy in this region.

Midrange: 500 to 2 kHz

The 'midrange' determines how prominent an instrument is in the mix. Boosting around 1000 Hz can give instruments a horn like quality. Excess output at this range can sound tinny and may cause ear fatigue. If boosting in this area, be very cautious, especially on vocals. The ear is particularly sensitive to how the human voice sounds and its frequency coverage.

Upper Midrange: 2 kHz to 4 kHz

Human hearing is extremely sensitive at the 'high midrange' frequencies, with the slightest boost around here resulting in a huge change in the sound timbre.

The 'high midrange' is responsible for the attack on percussive and rhythm instruments. If boosted, this range can add presence. However, too much boost around the 3 kHz range can cause listening fatigue. Vocals are most prominent at this range so as with the 'midrange', be cautious when boosting.

Presence: 4 kHz to 6 kHz

Cutting in this range makes sound more distant and transparent.

Brilliance: 6 kHz to 20 kHz

The 'brilliance' range is composed entirely of harmonics and is responsible for sparkle and 'air' of a sound. Boost around 12 kHz make a recording sound more Hi Fi.

Over boosting in this region can accentuate hiss or cause ear fatigue.

Summary Table of Frequency Ranges
  • Sub-Bass: 20 - 60 Hz, Power, rumble
  • Bass: 60 250 Hz, Boom, thump, fat
  • Low-Midrange: 250 500 Hz, Full
  • Midrange: 500 2000 Hz, Horn , cheap
  • Upper-Midrange: 2000 4000 Hz, Prominent, Horn
  • Presence: 4000 6000 Hz, Clear, bright
  • Brilliance: 6000 20, 000 Hz, Air, sparkle
« Last Edit: December 28, 2012, 09:34:04 PM by audiomuze »
I like beautiful melodies telling me terrible things -- Tom Waits

Free your mind...and your ass will follow.