Audio Frequency Spectrum Explained

(Last Updated On: December 12, 2018)

Have you ever wondered what those numbers on the back side of some audio device packaging mean? We bet you have. Among the information about impedance, SPL, etc. there is one that is very important for us right now and we want to give you a thorough explanation of what it means and what it says about our devices.

As you have probably guessed, we are talking about frequency response. It is expressed in Hertz (Hz) and it’s different for every audio device. It is given in a form of range (for example – 18Hz-22kHz). This range tells us the lowest and the highest frequency some audio device (speaker, headphones) can deliver. The frequencies within the range that a human ear can hear are called audible (or audio) frequencies and this range is known as our audio spectrum.

Audio Spectrum

The property that makes it possible to define a sound as high or low is the pitch. It can be determined only in terms of clear and stable frequency, which makes that very sound distinguishable from common noise, and it is one of the sound attributes (along with timbre, duration, and loudness). Although some consider it objective property, the pitch is more subjective attribute because people define sound characteristics in different ways. If one person considers that a certain sound is high, the other doesn’t have to feel the same way about it. We all generally agree about sounds being high or low but there are some nuances in sound perception. This is the main difference between frequency and pitch – while frequency is an objective characteristic that can be measured, the pitch is more like a subjective sound perception that can’t really be measured.

What is the Audio Frequency Spectrum?

As all of you probably know, the range of audible frequencies (audio frequency spectrum) spans from 20 Hz to 20 kHz. Just like every device is different, every human ear is different and audio spectrum of every one of us is different. This means that not all of us hear the same sounds or all the sounds. Some of us will hear deeper or higher sounds than others but, on average, we can all hear the sounds within the mentioned spectrum.

The frequencies below 20 Hz are extremely deep. They are, in fact, so deep that they are hardly audible. Experts love to say that they are more felt than heard thanks to their great vibration amplitude. On the other hand, frequencies above 20 kHz are so high that they can cause severe hearing problems as well as hearing loss. The high sounds are actually considered noise or, simply, nebulous sounds.

As far as 20 Hz – 20 kHz spectrum is concerned, we can divide it into several frequency bands that affect the sound (as a final product) in different ways. The bands we are talking about are sub-bass, bass, low midrange, midrange, upper midrange (high-mids), lower treble, and highs. If you stay with us, we will explain what they refer to, how they affect the sound, and what kinds of instruments can produce different frequencies.

Sub-bass (20 Hz – 60 Hz)

Sub-bass frequency band refers to the deepest and the lowest sounds within the range audible to the human ear. We have mentioned that the tones lower than 20 Hz are better felt than heard but we can say the same thing for the tones within 20-60 Hz range. They are extremely powerful and very strong. All of this is proved by the fact that most of the instruments can’t produce sub-bass tones except for a few that have a low pitch (bass guitar, tuba, bass trombone, harp, etc.). Too much boost in this area can lead to an excessively powerful sound that is quite unpleasant for listening.

Bass (60 Hz – 250 Hz)

Bass range, as you can see, is quite wider than the sub-bass range and, subsequently, more instruments can produce the tones that belong to this group. In fact, we can say that the tones within this range are the most important for the human perception of the bass in every song and that they define their richness and fullness. This can be proved by the fact that most of the modern songs have their lows in the range that spans from 90 Hz to 200 Hz. These tones can be produced by many instruments (cymbals, trumpet, saxophone, clarinet, guitars, violins, etc.) as well as male and female voices. If you boost them too much, you will get some kind of boomy sound that is also unpleasant for listening.

Low midrange (250 Hz – 500 Hz)

This range also belongs to the group of low tones but these can be produced by the majority of instruments. Some human voices (male and female) can also produce these frequencies. When the tones from this group are heard clearly, it can be said that the bass is present. If you boost a signal at approximately 300 Hz, you can add some clarity to the bass instruments but if you boost it too much at 500 Hz, high-frequency sounds become quite muffled.

Midrange (500 Hz – 2 000 Hz)

Midrange tones are extremely important for the general impression of a song. The way that an instrument delivers these tones affects its prominence and it determines if the instrument will stand out in the music mix or not. Boosting a signal around 1000 Hz can make the instrument sound like a horn. If you exaggerate, you can make things much worse, especially in human voice area. Remember that when it comes to the midrange, the most important thing is to deliver the vocals in the best possible way.

Upper midrange (2 000 Hz – 4 000 Hz)

The upper midrange is the area where the percussion and rhythm instruments can be noticed, especially if you boost it a bit. However, if you boost it too much, it may cause fatigue. Remember that vocals are very noticeable in this range, too and bear in mind that excessive boosting can have negative consequences in this area as it changes the tone color.

Lower treble (4 000 Hz – 6 000 Hz)

The tones in this frequency range are the ones that define the clarity of sound. Boosting some frequencies from this range can result in an unpleasant and harsh sound. In the opposite case, the sound can be quite distant and also unpleasant.

Highs (6 000 Hz – 20 000 Hz)

This is the area that can’t be accessed by all the instruments. These frequencies add some freshness to the sound and they are extremely difficult to deliver. Too much boost in this area can cause sound distortion and the appearance of some kind of hissing that can be extremely unpleasant for hearing and even cause hearing issues.

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