The Difference Between Types of Noise Colors

Sound frequency spectrum

I’ve found customers have increasingly been calling in seeking to learn more about noise and how they can best utilize it for therapeutic effects. This is amusing as an expert in acoustics where I spend much of my time figuring out how to eliminate noise via soundproofing and sound control solutions. That said, “noise” does in fact have two different meanings, or rather the technical definition of noise includes two diametrically opposed experiences for our ears – one bad and one good.

In common parlance, noise typically refers to sounds that are an annoyance, such as creaky floors and the sounds of traffic outside the window. These are the types of situations I routinely help customers find solutions for to create a more peaceful environment by either blocking distracting, irritating noise or toning it down. There are, however, versions of noise that do the opposite of annoy; they soothe. Examples include the sound of rustling leaves and ocean waves. While we don’t often call these sounds noise, that is technically what they are, and science has shown us their properties and how to recreate them to very positive effects.

In this article, I will untease the mystery of noise and explain what it is technically, how it can be used to improve your sleep, mood, and concentration, and also techniques to make your acoustical environment ideal to get the most out of utilizing therapeutic noise.

What is Noise?

The technical definition of noise is a random variation in a signal. This definition of noise is quite broad as it has meaning in signal processing, electronics, acoustics, and data processing. We are going to focus on acoustical noise, or the noise we hear. While acoustical noise usually is a problem and something we want to get rid of, curiously there are many sounds that are quite soothing that are technically defined as noise, too. Let’s look at the characteristics of noise so that we can determine whether it is soothing or irritating:

3 Characteristics of Noise

1. The Frequency Spectrum

Without delving too far into the science of sound, let us just say that frequency refers to the pitch of a sound. Low frequency sounds include drums and bass guitars while high frequency sounds include cymbals, soprano vocalists, and whistles. When it comes to frequency and noise, there is broadband noise that is made up of many different frequencies and narrowband noise that concentrates around specific frequencies. An example of broadband noise is ocean waves – a noise we would consider pleasing. An example of narrowband noise is the whistling of a kettle at boil, and no one wants to hear that sound longer than to know when the water is boiling and turn it off!

2. Amplitude

Amplitude refers to the volume of sound, and volume can be experienced via noise in three different ways: intermittent noise, continuous noise, and impulsive noise. Intermittent noise refers to noise occurring at irregular intervals, like the sound of a barking dog or the on and off of someone at work with a power saw. Impulsive noise refers to sudden, brief bursts of sound, such as gunshots and fireworks. Finally, we have continuous noise, which can be our friend or our foe. Examples include the sounds of traffic, the hum of an air conditioner, or that soothing sound of waves crashing on a beach.

3. Duration

Although somewhat related to intermittent and continuous noise, duration refers to how long noise lasts. The duration of noise is either transient or steady. An example of transient noise is the sound of a dog barking at a squirrel in the yard; the dog barks when the squirrel appears and then stops when it runs off. Steady noise, on the other hand, is exemplified by our favorite example of the ocean, as the “noise” of ocean waves never ceases and is constant.

Now, using these characteristics we can determine the types of sounds that we find pleasing rather than annoying. We want to make sure they are broadband noise filled with many frequencies for balance, are continuous so as to not be jarring, and are steady for as long as we want to hear them. As noted in each of the three characteristics above, the sound (noise!) of ocean waves crashing on a beach meet all of these, and it’s why it is the go-to example for natural sounds that we find pleasing to the ear. Other examples of pleasing noise from nature include rain, wind rustling leaves, rapids in a river, and even the sounds of thunder, although thunder technically is an impulsive noise (more on that below).

The difference between these noises are identified as the noise color. Before listing the noise colors and their applications for therapeutic effects, let’s briefly untangle how a noise can be a color in the first place.

Why Noise is Classified by Colors?

For the musicians out there, you’ll be familiar with the concept of timbre, or “tone color.” Timbre is the characteristic we use to differentiate between two sounds that have the same pitch and loudness. For example, a piano and a violin can play the exact same note at the same loudness and sound completely distinct. While there is a technical explanation for this, we make it easier to understand by simply calling it the tone color, or timbre.

Noise color is similar but also involves an analogy to the color spectrum, as light waves are also classified by their frequency, just like sound waves. The easiest way to understand this is how white light is actually made up of all of the colors in combination. This is why the most common type of noise is called white noise. Now, let’s look at all of the noise colors and what makes them unique from one another.

Types of Noise and the Differences Between Them

There are six colors of noise, three of which are ideally suited for beneficial effects including better rest, relaxation, and concentration:

The 3 Best Noise Colors for Relaxation, Sleep, and Concentration

White Noise

You’ve likely heard of white noise as it is the most common color of noise. White noise is characterized by a constant power spectral density and therefore is equally intense across all frequencies, thus the analogy to white light. It is the definition of broadband noise and is often referred to as such. White noise is an artificial noise borne of electronic signals and sounds like a constant hiss, such as static or the sound of an old television set.

Applications for White Noise

White noise is most often used to provide a calming sound to improve sleep, specifically to help infants sleep, as well as sound masking. Interestingly, it is very often used in music, notably electronic music, to “fill out” the sonic space and make it more interesting, although it is kept in the background and hard to hear specifically without a discerning ear.

Pink Noise

While white noise was the first color noise to find interest due to its prevalence in radio and decades of television sets, pink noise has become the modern go-to for therapeutic effects as it’s more soothing. The reason it is more soothing than white noise is because the power density decreases 3 decibels per octave, meaning there is a more balanced distribution for the human ear because lower frequencies are slightly louder. Pink noise is the type of pleasing noise found in nature, such as ocean waves, steady rainfall, and wind rustling leaves.

Applications for Pink Noise

Because pink noise offers an enhanced balance as compared to white noise, it is a better choice for sleep therapy, relaxation, and a less intrusive background noise for concentration.

Brown (Red) Noise

Brown noise is similar to pink noise but its power density decreases by six decibels per octave rather than three. This correlates to even more energy at lower frequencies/less at higher frequencies. The result is a deep, rumbling sound, such as thunder, waterfalls, and rapids in a river.

Applications for Brown (Red) Noise

Due to the soothing rumble of its enhanced lower frequencies, brown noise is the optimal choice for relaxation. It is best described by the rumble of thunder, which is a great noise to hear when relaxing with a book or taking a short nap, but a bit disruptive for deep sleep as compared to pink noise.

The Other Three Noise Colors

The other three noise colors of note aren’t suited for relaxation, concentration, or sleep, but can be useful in acoustic therapies for

Blue Noise

Blue noise is a type of noise where the power doubles as the octaves increase, meaning it is the opposite of pink noise as it sounds sharp and high-pitched. Blue noise is utilized in signal processing and dithering.

Violet (Purple) Noise

Violet, or purple, noise is like blue noise but even more extreme. As octaves increase, the power spectral density rises by 6dB, emphasizing the higher frequencies even more. It has few use cases but may be utilized in scientific research.

Gray Noise

Finally we have gray noise, which is white noise that is adjusted so that the have equal perceived loudness across its frequency spectrum. This means that it sounds a bit more balanced and equal than white noise, but still has the artificial quality, unlike pink noise. Gray noise is utilized in hearing testing due to its equalized perceived loudness.

Improving Acoustics for Optimal Noise Playback

Sometimes the problem with a quiet space isn’t that it’s quiet, it’s that the silence amplifies unwanted noise and/or reverberation. For therapeutic noise to be most effective, it’s imperative that you rid unwanted noise from elsewhere via soundproofing techniques and make sure reverberation and echo isn’t a factor with sound control techniques. As it regards the latter, even just placing an acoustic panel or two, such as AlphaSorb® Fabric Wrapped Acoustic Panels, can make the positive attributes of therapeutic noise that much better.

Solve Your Acoustics Appropriately To Get the Most Out of Therapeutic Noise

Noise, ironically, is a surprisingly fantastic way to achieve better sleep, aid in concentration, and help us to relax. To make the most out of therapeutic noise like white, pink, and brown noise, it’s ideal to make sure your space has quality acoustics. I always recommend quality acoustic panels in the bedroom or a living room to make it the most inviting and relaxing space where we can rest and relax.

To learn more about how to upgrade the acoustics no matter the space and give therapeutic noise the right foundation to impart positive results, give me a call today.

To learn more about how Acoustical Solutions can solve your noise control problems, use our contact form, call one of our Acoustical Sales Consultants at (800) 782-5742, or visit us on the web at acousticalsolutions.com.