Frequency range at a glance

What does audio frequency mean?

Audio frequency refers to the rate at which sound waves oscillate or vibrate, producing the sensations of pitch and tone that our brain interprets as sound.

Sound waves are essentially vibrations in air pressure that travel through the air and reach our ears, where they are converted into electrical signals and processed by our brain.

The frequency of a sound wave is measured in Hertz (Hz) or Kilohertz (kHz), which represents the number of cycles or vibrations per second.

The higher the frequency of a sound wave, the higher the pitch we perceive. For instance, a sound wave with a frequency of 20 Hz would be a very low-pitched sound, while a sound with a frequency of 20,000 Hz (20 kHz) would be a very high-pitched sound.

Our auditory system is sensitive to a wide range of frequencies, typically from 20 Hz to 20 kHz. However, as we age, the ability to hear higher frequencies tends to degrade due to various factors, such as natural ageing, exposure to loud noises, and other environmental influences.

Moving up an octave in terms of audio frequency means doubling the frequency. For example, if a note has a frequency of 200 Hz, moving up one octave would result in a frequency of 400 Hz. This doubling of frequency gives the sound a higher pitch but retains the same fundamental note.

Every sound we hear is composed of a fundamental frequency and harmonics. The fundamental frequency is the lowest and most audible pitch of the sound. When a sound is produced, it also generates higher frequencies at integer multiples of the fundamental frequency, known as harmonics. These harmonics give the sound its characteristic timbre and brightness.

The presence and distribution of harmonics are what distinguish different musical instruments or voices even when playing the same fundamental note.

In music, the audio frequency range is critical for creating different notes and tones. Musical instruments are designed to produce specific frequencies to achieve desired pitches. For example, the lowest note on a piano is typically an A with a frequency of 27 Hz, and the highest note is a C with a frequency of 4186 Hz.

By manipulating audio frequencies, we can create melodies, harmonies, and complex sounds that evoke emotions, enrich storytelling, and add depth to our auditory experiences.

Ranges in the audio frequency spectrum

Sub-bass

The sub-bass region, spanning from 20Hz to 60Hz, is a challenging part of the frequency spectrum. It houses the deep foundation of sound, often felt more than heard, lending a sense of raw power to music.

This domain is occupied by instruments like kick drums, the lowest piano notes, bass synthesizers, and certain orchestral instruments such as the harp and tuba. However, most instruments struggle to enter this range due to its extremely low frequencies.

To accurately reproduce it you’ll need quality headphones, full-frequency speakers, or subwoofers; speaker design and woofer size influence the amount of bass produced.

Applying EQ adjustments to this region should be done carefully as excessive boosting can lead to overpowering sound, while excessive cutting weakens the audio and blurs frequencies.

Bass

The bass region houses frequencies 60Hz to 250Hz and forms the foundation of the audio spectrum. Accurate reproduction of this range demands more power as it’s not very sensitive to human ears. This means you’ll need powerful amplifiers or headphones with minimal distortion.

Boosting or adjusting this range can profoundly alter sonic characteristics. A moderate boost enhances warmth and presence, while excessive boosting leads to muddiness and boominess.

Instruments like bass guitars, lower notes of pianos, and the body of drums fit into the bass range and they all shape the thickness of sound. It’s pivotal for rhythmic elements, with many bass signals in modern music concentrated between 90Hz and 200Hz.

Frequencies around 250Hz can give warmth to the bass without sacrificing definition. Termed the “lows” or “low-end,” this range can tip the balance of music, influencing its thickness.

Lower midrange

The lower midrange spans from 250Hz to 500Hz and is a super important part of the audio spectrum for shaping the character of sound. It houses the fundamental frequency of numerous acoustic instruments, such as brass instruments and woodwinds like alto saxophones and clarinets. The low-order harmonics of most instruments also reside here, adding richness and complexity to their tonal profiles.

Boosting around 300Hz enhances clarity in bass and lower-stringed instruments, while excessive boosting around 500Hz can muffle higher-frequency instruments. This region holds the key to depth in instruments like the voice, cello, bass guitar, and snare drums; deficiencies in this area can lead to sonic shallowness.

Balancing this range is essential for maintaining clear and well-defined audio, especially as it’s crucial for defining the fundamental pitches of many instruments!

Midrange

The midrange, from 500Hz to 2kHz, dictates the prominence and texture of instruments in a mix. For instance, sound engineers and producers often focus on this range when they want music to “pop” out of the speakers or headphones.

Boosting around 1000Hz can lend a horn-like quality to instruments. Boost too much – in the 1kHz range – and you can end up with a metallic quality that will potentially lead to listener fatigue. Particularly when dealing with vocals, caution is advised while boosting in this area, as the human ear is especially sensitive to vocal sounds and their frequency coverage.

Beyond the fundamental frequency and lower harmonics or overtones, the midrange adds clarity and detail to the sound.

Upper midrange

The upper midrange of the audio frequency spectrum, between 2kHz and 4kHz, is where the harmonics of instruments with lower fundamental frequencies are found. This region significantly influences the clarity and character of these instruments.

Human hearing is particularly sensitive to this range; even minor boosts lead to noticeable changes in timbre. It’s where consonant and plosive sounds like ‘p’ and ‘s’ reside, making it crucial for clear speech and singing.

The ear canal naturally resonates around 3.5kHz, naturally emphasising this area. This means you should be careful when boosting the upper midrange – it can add presence, but too much can cause listening fatigue.

Percussive and rhythmic instrument attacks are defined by the high midrange. For voice-centric genres like choral music, opera, or podcasts, headphones or speakers that excel in this range are beneficial.

Presence

The 4 to 6kHz presence region can make or break the detail of your sounds. Shaping sound clarity and definition, this range is where harmonics for instruments like the violin and guitar lie. If you boost the presence in your mix, you’ll enhance the clarity and articulation.

Many home stereos centre their treble control around this frequency band due to its significance in defining upper-range details.

When well-reproduced and clear, the presence range creates an immersive listening experience, as if the music is being performed right in front of you. However, over-boosting can lead to an annoying, harsh quality that can be distracting. Conversely, cutting in this range can create a more distant and transparent sound, though excessive cuts might diminish essential details.

Brilliance

The 6kHz to 20kHz brilliance audio frequency region is where high-frequency sheen and clarity come into music. Composed entirely of harmonics, this range imparts – as its name suggests – brilliance, adding sparkle and detail to the sound. The 10kHz range is particularly influential in affecting clarity, often referred to as the “air” band as we move upwards from this point.

This range is also where sounds become more like high-pitched whines and whistles. It includes sibilant sounds, which are the unwanted whistling noises sometimes heard when pronouncing an ‘s’, and the harmonics for certain percussive sounds like cymbals.

A boost around 12 kHz can give a recording a more hi-fi quality. However, boost carefully as too much brilliance can accentuate hiss and potentially cause ear fatigue. Therefore, balance is key to achieving a rich, detailed sound without discomfort.

Our favourite EQ plugins

FabFilter Pro-Q 3

The modern industry-standard, FabFilter Pro-Q 3 makes complex parametric EQ simple with its incredibly user-friendly interface.

Based around a modern drag-and-drop functionality, it does away with traditional controls and lets you edit up to 24 bands completely freely, adjusting each independently from bell filters, shelves, or filters.

Where traditional EQs provide no visual feedback, Pro-Q 3 features a customisable frequency analyser, highlighting any changes you’ve made to the output audio signal.

Following the ultra-modern theme, each band can be dynamic. This mode lets you set a threshold at which EQ will only apply processing when the audio level crosses the threshold, creating a highly natural and transparent EQ tone.

How audio frequency range affects enclosure design

When engineering an audio system, be it for a home, car, or portable device, the audio frequency range profoundly influences enclosure design, constituting a delicate balance between size, cost, and quality.

The size of the speaker and enclosure are intrinsically linked to frequency response. Low frequencies need a larger diaphragm for sufficient air movement as matching the perceived loudness of higher pitches requires greater air displacement.

Smaller speakers are suited to high frequencies due to their quicker response, reducing unwanted harmonics. This size relationship extends to the enclosure – smaller speakers enable compact enclosures, saving space and materials.

Resonance, characterised by an object’s natural vibrational frequency, directly affects enclosure design. Unwanted rattles and buzzing can arise if the enclosure resonates at the same frequency as the expected audio output. Careful enclosure design ensures resonance avoidance, while controlled resonance widens the resonance range based on application requirements.

Materials play a vital role in diaphragm construction. Diaphragms must be light enough for rapid response yet rigid enough to prevent deformation during movement. Choices like paper and mylar offer this balance, with mylar’s moisture resistance being particularly beneficial. Rubber connecting the diaphragm to the frame must be both sturdy and pliable to facilitate movement without interference.

There can be trade-offs when it comes to sensitivity, frequency range, robustness, and sound pressure level (SPL) across speakers and microphones. Speaker cone weight is more critical for higher frequencies, while lower frequencies need durable suspensions. Enclosure materials influence resonance and sound absorption, with lower frequencies requiring better damping.

FAQs

What is frequency range?

Frequency range refers to the distance between the lowest and highest frequency a piece of audio equipment can reproduce. It is measured in Hertz and is represented between the typical human hearing range of 20Hz to 20kHz.

Why is frequency range important?

Understanding the audio frequency range is key to understanding how sound works. It will help you grasp the technical specifications of audio equipment as well as provide insight into why music sounds as it does, allowing for adjustments (like EQ settings) to optimise listening experiences.

What are the frequency ranges in music?

The most common frequency ranges in music are as follows:

• Sub bass: 20 – 60Hz
• Bass: 60 – 250Hz
• Lower midrange: 250 – 500Hz
• Midrange: 500Hz – 2kHz
• Higher midrange: 2 – 4kHz
• Presence: 4 – 6kHz
• Brilliance: 6 – 20kHz

Final thoughts

The founding basis of how sound works, understanding the frequency range provides invaluable information for anyone with a keen interest in high-fidelity audio, audio equipment, and Hi-Fi systems or those looking to venture into music production.