A Multicoloured Symphony of Sound Noises

Sound noises, often referred to as ambient or background sounds, hold a unique place in the realm of auditory perception. These auditory textures, akin to the colours in a painting, encompass a wide spectrum of frequencies and amplitudes.

In the world of sound, beyond the symphonies and melodies, lies a sonic landscape that often escapes conscious attention—the realm of sound noises. These are ambient sounds that surround us, intricately woven into the auditory tapestry of our lives. Sound noises emerge from a myriad of sources, both natural and artificial. Think of the humming of your fridge, the sound of the rain or sea, the fan of your computer, distant voices and car traffic. It is a canvas splashed with colours, sound noises bring forth a palette of sonic hues, each evoking emotions and states of mind. They all contribute to the tapestry of sound noises and our auditory environment.

Good to note is that this article is about certain frequency ranges across the audible spectrum, not about we as human might consider as noise or the volume of sounds.

The Colours of Sound Noises

Much like colours in a painting, sound noises are diverse in their characteristics. The low rumble of a waterfall might elicit a sense of tranquility, while the rhythmic clatter of a train can evoke a contemplative mood. These auditory hues have been metaphorically associated with colours, such as the “blue noise” resembling the sound of ocean waves, or the “pink noise” akin to rainfall. These sonic shades offer a spectrum of emotional and cognitive experiences.

There are many coloured noises but the ones below are the most distinct:

1. Grey Noise:

Grey noise is characterized by equal energy per octave, rendering it perceptually flat across the entire audible frequency spectrum. It lacks the prominence of higher frequencies found in white noise.

Frequency Range: Throughout the entire audible range.

Use: Grey noise is often used for psychoacoustic studies, as it allows researchers to explore how humans perceive sound energy at different frequencies.

2. White Noise:

White noise exhibits equal energy across all frequencies, creating a consistent sonic spectrum akin to the static on a television or radio.

Frequency Range: Throughout the entire audible range.

Use: White noise is commonly used for sound masking, promoting concentration, and aiding sleep.

3. Blue Noise:

Description: Blue noise has a higher energy in higher frequencies, rendering it a sharper and more pronounced sound than white noise. It is akin to the sound of ocean waves crashing.

Frequency Range: Increases logarithmically with frequency.

Use: Blue noise finds application in audio testing, especially for assessing high-frequency capabilities of audio equipment.

4. Brown Noise:

Brown noise, also known as red noise, has more energy in lower frequencies (twice as strong as Pink noise), creating a deeper, rumbling sound reminiscent of a thunderstorm or a waterfall.

Frequency Range: Decreases logarithmically with frequency.

Use: Brown noise is favoured for relaxation, stress reduction, and aiding sleep. Recently a lot of articles have popped up of the use of brown noise to help focusing when you have ADHD.

5. Pink Noise:

Pink noise has equal energy per octave, resulting in a balanced frequency spectrum that decreases as frequency increases. It has a smoother and more natural sound compared to white noise.

Frequency Range: Throughout the entire audible range.

Use: Pink noise is beneficial for enhancing focus, improving cognitive performance, and aiding relaxation.

6. Violet Noise:

Violet noise, also known as purple noise, emphasises the highest frequencies, making it a sharper and crisper sound compared to white noise. It resembles the hiss of a high-powered waterfall.

Frequency Range: Increases logarithmically with frequency, with higher energy in higher frequencies.

Use: Violet noise has potential applications in improving hearing sensitivity and aiding auditory processing.

Deeper into coloured noise

In the book Sonic wonderland, A Scientist Odissea of Sound by Trevor Cox he mentioned that he moved his head from side to side, voices in the room change as if someone was rapidly altering the settings on a hi-fi’s graphi equaliser.  This colouration was caused by a change in the balance of the sound, with some frequencies being boosted while others were suppressed. In short he was experiences noises this is what he had to say about the colouration of noises:”

It might seem odd to talk about the colour of a sound …The link between colour an sound goes back many centuries, with Sir Isaac Newton spotting the similarity between the distance his prism spread out light colours and the lengths of strings needed to sound out a musical scale”

Trevor Cox mentions that also today, acoustic engineers use terms as ’white and ‘pink’ noise. In a way it is similar as he explains when paints are mixed together the frequency balance of the reflected light changes from the original colours presenting a different colour. He explains further that blue paint reflects light of a higher frequency than red paint and therefor acoustic engineers use colours to describe the dominant frequencies in sounds,

What is interesting is that he also found that sound most likely influenced the way our ancestors painted. He mentions acoustic archaeologist Steven Waller who wrote a paper on this subject. (We delve into this subject in another blog) apparently the sheer volume of evidence that prehistoric rock art was influenced by cave acoustics is growing. But Cox does refer to David Lubman, a retired aerospace engineer who has been applying acoustic science to archaeological sites, warns that correlation does not necessarily mean causation.

Benefits and Negatives

The benefits of sound noises are multifaceted. They can mask intrusive sounds, enhancing concentration and aiding relaxation. Studies (see below this article) highlight the positive effects of sound noises on cognitive performance and stress reduction. However, excessive exposure to certain sound noises can lead to noise pollution and even adverse health effects. Our world is increasingly becoming louder and louder. Interestingly enough these coloured noises can be used to mask the “noise” from the world around us helping us to relax or focus. Also there are more and more experiments and research is done to find the benefit of these noises for healing in hospitals, to enrich musical soundscapes and increase productivity in normal noisy environments.

Brain processing

The human auditory system’s response to sound noises is an interplay of neural processes. When exposed willingly to sound noises, the brain’s default mode network can deactivate, promoting mindfulness and concentration. Neuroimaging studies, such as those by L. Liikkanen (see the last one of the list, below this article), illuminate the brain areas involved in processing sound noises, shedding light on their cognitive and emotional effects. The world of color noise offers a diverse spectrum of auditory experiences, each with its unique frequency distribution, emotional impact, and cognitive effects.

Self Help versus the research

If you are inspired to start listening consciously to noises it is good to note, most scientific research on this subject is not a 100% clear on how often, how to use, what colour to use exactly for what kind of mental effect you want to reach. Wether it is to focus, to mask sounds or fall asleep or stay asleep, the best advice we can give you is to experiment with the different noises in different situations. You can use the description of the colours above as a starting guideline. Experiment with different factors: the colour, the volume and the exposure time and see what works best for you. Our tracks are made in such a way you can easily put them in a loop. To read further at the bottom of this articles are some interesting links.

You can purchase our album with the different noises here: @claudio

Interesting research and articles to delve into:

Spectral Content (colour) of Noise Exposure Affects Work Efficiency: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7986458/

Effects of masking sound on train passenger aboard activities and on other interior annoying noises: http://www.diva-portal.org/smash/record.jsf?pid=diva2:341431&dswid=-2379

Effects of sound source localization of masking sound on perception level of simulated tinnitus: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8795453/

Unintended Consequences of White Noise Therapy for Tinnitus-Otolaryngology’s Cobra Effect: A Review https://pubmed.ncbi.nlm.nih.gov/30178067/

Cognitive Performance and Sounds: The Effects of Lyrical Music and Pink Noise on Performance

https://inside.nku.edu/content/dam/gero/docs/NYSA/Nysav1/Chitwood_Cognitive Performance and Sounds.pdf

Different Effects of Adding White Noise on Cognitive Performance of Sub-, Normal and Super-Attentive School Children https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4231104/

The Effect of Noise Exposure on Cognitive Performance and Brain Activity Patterns: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6901841/

Background white noise and speech facilitate visual working memory: https://www.biorxiv.org/content/10.1101/2020.04.07.030114v1.full.pdf

Can pink noise help you fall asleep

https://www.sleepfoundation.org/noise-and-sleep/pink-noise-sleep

Musical activities predispose to involuntary musical imagery

https://journals.sagepub.com/doi/abs/10.1177/0305735611406578

To read more in sound in general and also noises we can recommend: Sonic wonderland, A scientist odissea of sound by Trevor Cox

If you are interested in de description and the technical aspects of the colour noises we can recommend the wikipedia page https://en.wikipedia.org/wiki/Colors_of_noise#White_noise