Audio Frequency Spectrum Explained

Music is a universal language. Most of us find it fascinating to study the science behind the audio frequency spectrum and its ideal balance in search of the perfect sound. We use Hertz (Hz) as a measuring unit for sound frequency, resulting in the multiple categories and classifications under it.

Every living organism has a unique interpretation level of sound observed. For example, the audible frequency range of an average person after birth lies between 20Hz to 20kHz. This article focuses on an intricate piece of the audio frequency spectrum in the simplest form possible.

What is the Audio Frequency Spectrum?

The frequency ranges that the ear of a human can interpret is what we refer to as the audio frequency spectrum. Another term used to describe this concept commonly is the sound frequency spectrum. As one grows older, so does the range degrade over time. The damaging of your ear potency is associated with multiple factors, the most prominent one being the aging effect. This range dictates what we hear in terms of music, frequency or pitch. Expanding your knowledge on the topic in question can come in handy in your daily activities.

One of the many advantages of understanding the audio frequency spectrum is that one gains confidence when discussing sound, especially its technical subjects. You will also understand technical specifications better and develop a simpler route to explain to other parties. For those who face problems when adjusting graphic equalizers, this is the long-term solution for your troubles. This knowledge also plays a role in your hearing capabilities as one gets to acquire a more profound definition of quality sound & improving your hearing.

The information available related to this concept appears complicated and its terminologies are technical. This trait makes it almost impossible to effectively spread the word and is most likely to complicate its understanding. Our final expectations will be to advance your knowledge of common subjects under the topic.

What Are Sound Frequencies?

The basic concept of sound is that it is relative to vibration. For example, if you make a musical sound in a medium like air, its molecules must vibrate to create audible sound. After these vibrations come into contact with our ears, our eardrums vibrate at the same frequency, converting the signal to brain interpretable electric signals. Although musicians opt to refer to the vibration as pitch, most of us refer to this sound property as frequency.

The audio frequency spectrum refers to the number of times when a sound wave repeats per second. Frequency is directly proportional to pitch- the greater the frequency, the higher the perceived pitch.

The image above is a digital representation created using a digital oscilloscope, and it represents a single cycle of a sine wave. Note that the most basic sound we can produce is the sine wave. The complete length of the cycle runs from point A to B. Since frequency is measuring sound in cycles per second, the lower the frequency value, the slower its cycling speed. For example, a sound sample that features a frequency of 20Hz means that its cycling is twenty times in every second. In another example, a sine wave of 10kHz will cycle incredibly fast, precisely ten thousand times a second.

Representation of Sound to Listeners

Most music listeners do not have access to oscilloscopes, complicating the interpretation and explanation process. It is for this reason that a meaningful representation is necessary for the successful analysis of basic sounds. A trait that most individuals ignore concerning music is its complex nature. To ideally dissect its properties, graphic representation tools are practical, regardless of hardware or software forms.

Music entails more than just basic tones. It is a mixture of thousands of frequencies that correctly blend to birth one uniform rhythm. In graphic equalizers, one gets access to knobs that manipulate all these frequency ranges and adjust the music’s spectrum and tone. The field is divided into multiple classifications making it easier to control and describe.

The Seven Frequency Bands

Sub-Bass; 20 to 60 Hz

The sub bass allows you to manipulate the low frequencies that appear first on most sound waves. The deep bass found here serves the purpose of being felt over being heard, giving a sense of power. Its range is from 20 to 60 Hz. More power from your amplifier is necessary to reproduce the low range sound, having factored out any distortions.

Only bass-heavy instruments can achieve this frequency range as the others find it hard to maintain the sound wave’s tempo and potency. An excellent example of a musical instrument that can quickly enter this frequency range is the bass guitar, and it has the lowest achievable pitch of 41 Hz. The Fletcher Munson Curves make it difficult for one to hear this pitch at low volumes. Although the earth-shaking properties of the range are impressive, excessive manipulation might leave your music muddy.

We recommend no equalization boost in this region without using quality monitor speakers. On the one hand, excessive boosting in the sub-bass range will make the sound overly distorted. On the other hand, too much curtailing can lead to an overly anemic low end.

Bass; 60 to 250 Hz

The bass range is the primary determinant of how fat or thin the sound is. Coincidentally, it is the range that most individuals are familiar with and passionate about in music. Under this region, the fundamental rhythm notes are centered, proving their importance and effect in every musical compilation.

Most of the bass signals present in modern music revolve around the 90-200 Hz bracket. Those aiming to add a feeling of warmth without losing definition to the bass go for 250 Hz, making for a more detailed vibe.

One crucial factor to note is that perfect recreation of the range requires more power than the other fields. Factors like speaker designs and subwoofers also play a vital role in the representation of this range. Boost in this area needs to be moderate for ideal results. Note that excessive boosting in the bass region might result in a boomy and irritating sound.

Low Midrange; 250 to 500 Hz

The low midrange bracket comes third in our frequency band analysis. All the low order harmonics of most instruments fall under this grouping, and specialists refer to it as the bass presence range. Boosting the signal to around 300 Hz tends to enhance the bass clarity and lower-stringed instruments. If this range is not heard accurately, the instruments and vocals may sound unnatural.

Boosting it past the 500 Hz mark can muffle the high-frequency instruments, lowering the quality of the sound produced. Also, excess energy in this region can sound muddy, as is the case in many songs. Every time music lacks depth in its instruments, the problem associates directly with the lower midrange section.

Frequency Response from Reference Audio Analyzer

Midrange; 500 Hz to 2 kHz

The midrange is responsible for how prominent an instrument is in a frequency mixture, and its values range from 500 to 2000 Hz. Under this range, the content of the dialogue, vocals, films, and sound effects reside, ascertaining its importance to the audio frequency spectrum. Products that focus their output in this range include headphones, mobile phones and speakers. Settling for 1000 Hz provides a horn-like quality to the sound produced.

When boosting this grouping, be cautious on vocals and other vital aspects of sound and music. The sensitivity of the ear is high when it comes to human voice sounds and frequency coverage.

Upper Midrange; 2 to 4 kHz

The upper midrange is the range where human hearing is most sensitive to the sound frequency band range. Even the slightest twitch can bring about a significant impact on the sound quality and timbre. Consonant sounds, for example, k, p, and s are most heard under this range. For this reason, we find it better to reduce manipulation of this range and stick to an ideal setting for satisfactory results. Because of our ears’ evolution and design, the ear canal naturally resonates with the sound intake to around 3.5 kHz.

To better understand this range, let us look at the canal as an in-built amplifier since it allows one to pick up sounds within range better. If the music is lacking in this range, we will notice immediately. The opposite is also true because excess emphasis often leads to sharper leading edge transients. When auditioning for headphones or speakers, this is a pivotal aspect to focus on as reproduced midranges dictate quality.

It is the role of the upper midrange to attack percussive and rhythm instruments. If boosted correctly, the range may add presence to your sound sample. However, over-boosting past the 3 kHz range will result in listening fatigue. Take extra caution on vocals when boosting since they are most prominent within this midrange.

Treble; 4 kHz to 6 kHz

Everything related to clarity and definition of sound falls under the presence range. An example of this range at work is in most home stereos. These devices center their treble control under this grouping, improving the sound quality significantly. If this range is correctly constructed and straightforward, one gets a similar feeling to sitting in front of a live performance.

You may have come across remastered classic albums. The remastering procedure is boosting the presence of music that replicates modern sounds or music made using modern production techniques. The correct balancing of this range adds warmth and sweetness to synths, high strings, and orchestral music.

Over boosting this range may provide a harsh sound that is irritating to the human ear. Cutting or extremely limiting the scope can make the sound appear distant and somewhat transparent.

Upper Treble; 6 to 20 kHz

The upper treble or brilliance range is our final range in the seven audio frequency bands analyzed in this article. Its entire composition is harmonics and is responsible for the air and sparkle of a sound. Boosting it to around 12 kHz enhances the recording of Hi-Fi quality. The 10kHz is the ideal range for optimal clarity and is heard as a high-frequency sheen, giving music detail and sparkle.

The “air” band is a term used to describe any value over 10 kHz under this classification. Musically, there is no word to describe this state, but one can imagine the air getting excited during a musical performance. Over boosting in this region can bring out an accentuate hiss and ear fatigue to its listeners.

Harman Curve Target

Frequency responses are often heavily relied upon for the final tuning of headphones or earphones. In fact, Sean Olive (then senior fellow at Harman International) performed blind tests on headphone listeners to see what sound most users preferred. The result of his studies culminated in the well known ‘Harman Curve‘ which had formed the building block for a universally praised frequency response.

Image result for ideal harman curve

Frequently Asked Questions

What is the Best Sound Frequency?

20 to 20,000 Hz is considered and accepted as the audible range of frequency. It is from this limit that most headphones are built on, while others feature a higher response. Despite the difference in values, higher frequency responses do not automatically accommodate better sound quality.

How Does Hz Affect Sound Quality?

Hertz, Hz, is the standard unit for measuring sound frequency. Generally, waves with high frequencies appear closer to each other, resulting in shorter wavelengths, while low-frequency waves are widely spaced and feature long wavelengths. It shows that frequency has a significant effect on wavelengths, which determines the quality of sound produced.

Image result for high frequency vs low frequency waves

Does Higher Frequency Mean Louder Sound?

A high frequency does not produce a loud sound. Instead, it results in a high-pitched sound and can only apply to sounds with a purpose, such as music. For one to create a loud sound, you will need larger vibrations. This concept is also called high amplitude- the vibration is directly proportional to the sound produced.


It is right to claim that our ears can ingest and digest more information than any other sense in the human body. When the frequency balance is ideal, our listening experience is elevated. The knowledge shared in this article is enough to improve how you handle yourself in audio frequency spectrum subjects. In addition, it is useful to know how the different portions of the frequency spectrum convey different traits for a headphone or in-ear monitor. By now, you are fully equipped with the technical and subjective concepts that revolve around music and its creation whether it be for the purposes of music listening or comprehending audiophile terminology.

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