What is noise? An unwanted sound that emerges at some point in life to annoy you.

You’re pro at trying to avoid it: you either close your ears, talk to the source of noise in an attempt to get them to quiet down, or simply run away from it. Worst of it all is trying to endure it.

But did you know that it’s not always annoying when it comes in colors?

Yes, noise has colors and you should buckle up because we’re getting sciencey!

Where do noise colors come from?

Now, although you don’t see or hear the noise color itself, you still hear the multiple superimposed sound waves of different frequencies that have color names. For clarification, frequency is the vibration of waveform per second (measured in hz).

Fair warning, this has nothing to do with the type of synesthesia where you see a color and start hearing certain sounds or frequencies. The phenomenon of synesthesia doesn’t limit you to hear colors alone.

Moving on, noise consists of infinite single source frequencies and it’s impossible to measure the power (amplitude or size of waves) of each frequency through hardware. For this reason we divide the frequencies on the noise spectrum  into bands such as 0-1khz, 1-5khz, 5-10khz, 10-15 khz and so on.

Then we measure the noise power per unit of bandwidth using spectral analysis. The number of divided bands depends on the measuring hardware and application needs.

The noise power is calculated for each band with the measurement of watts per second. This means we measure watts of energy that emit every second. Bear with me here because that’s when each band gets its color name.

What colors are there?

Warm colors like brown and pink assign to low frequencies and colder colors like blue and violet assign to high frequencies. White color is when all the frequencies are present in equal manner. Take a look at the noise spectrum as we go over each one in more detail.

White Noise

It’s no news that white color contains all 7 colors of the rainbow. Almost the same principle works for the noise spectrum as well. All the bands of frequencies that are equally present in the spectrum make up the white noise.

If you take a look at it, you’ll see flat spectral density. It’s also present in case of red, blue and green (RGB) colors producing the same intensity, since the noise colors are an analogy to the light colors.

white noise image

White noise can be used for a variety of cases since its frequencies are mainly audible to the human’s ear ranging from 20 Hz up to 20 kHz. White noise is widely present in music, specifically in percussion instruments. It is also used to help people who suffer with tinnitus and people who have trouble sleeping.

That is because our brain can determine a single source frequency, but it becomes difficult to hear multiple. White noise serves as a blocker for other background noises and makes our brain diminish them. Therefore, you can use it as sleep noise.

If you think of it, our Krisp helps diminish the background noises in real time too, except for it’s more powerful and can suppress the white noise as well and it doesn’t need to trick our brain into it. The only thing is that you have to be in a call, so that it cleans both your noise and the other speaking person’s noise. Try Krisp yourself to test it.

Coming back to our white noise, it sounds very similar to what you hear when you see a snow screen on the TV. Noise on TV appears in case of no transmission signal coming through the antenna receiver. It displays static dots (pixel patterns) all over the screen and represents the random electromagnetic noise that the antenna manages to catch.

Listen to the white noise before we move on to the next noise color, and just a heads up – you may want to lower your volume first:

Pink Noise

Pink noise is otherwise referred to as flicker noise or inverse 1/f noise since its spectral power density decreases with 3 dB per octave. Thus, the power of the pink noise band is inversely proportional to the frequency – the higher the frequency the lower the power. Pink noise appears much louder in lower frequencies.

Why exactly is it pink? Because pink noise spectrum emphasizes the lower frequency with warmer colors like red (brownian noise). So relative to the white noise, pink noise gets a red glow and becomes pink.

white noise and pink noise image in comparison

It is mainly utilized by scientists to test flat frequency responses, but it can also serve as a tool to diminish low frequency background noises. In fact, according to a study conducted by Neuron journal showed that people actually fall into deep sleep better with pink noise stimulation.

Listen to your heartbeat – you’ll be surprised but its rhythm has a pink noise pattern too.

Now listen to the pink noise itself, it sounds a lot milder and balanced as opposed to white noise and it seems to have a bass base:

Brown Noise

Brown (also referred to as red) noise is known as the Brownian noise. It’s said to describe distant ambient noise of underwater. In fact, that’s where the “Brownian” term is derived from – particles that randomly move in any liquid. If you are curious about the full scientific term of particle movement, it’s Brownian motion or pedesis.

Brownian is a deeper version of pink noise since it’s spectral power density decreases by 6dB per octave, so it’s inversely proportional to frequency by 1/f^2. Again, it has more power in lower frequencies.

Thanks to the reduced high frequencies in brown noise, it is widely used with focus improvement and can also aid your studying and sleeping routine.

brown noise and pink noise image in comparison

You’ll find brown noise a lot quieter than pink noise. Both of them are relatively more soothing sounds than the bright white noise.

Listen carefully, you may associate it with a mild underwater feeling similar to your blood flow sound when you put a seashell to your ear. 🙂

Blue Noise

Blue noise (also known as azure noise) is the exact opposite of pink noise, since its emphasis is on higher frequencies. It is proportional to the frequency by f – the higher the frequency the higher the power. The power density of blue noise has an increase of 3dB per octave. So, if we put it simpler each octave has the energy of the 2 previous octaves together.

blue noise and pink noise image in comparison

Blue noise is a good option to apply for processing digital audio and video data, to avoid color banding in images or other similar large-scale patterns. This is otherwise known as dithering.

For example, it can be used for turning a grayscale image into a black and white one to compensate the average gray level with dense enough black dots.

Get familiar with blue noise below. It’s a bit more straining to the ear because all the emphasized energy is in high frequencies.

Violet Noise

Violet noise (also called purple noise) is in its turn the opposite of brown noise, with power density increasing by 6 dB per octave. It is proportional to frequency by f^2.

blue noise and violet noise image in comparison

Violet has a lot of power in high frequencies which is why it will be a lot more annoying to listen for a long time. However, it can still be helpful with diminishing high frequency background noises and specific cases of tinnitus or hearing loss.

Here you go, be careful as you listen or rather turn the volume down, since it’s loud and irritating to the ear.

Grey Noise

Grey noise is a bit more complicated. Look at the curve, it’s an inverted A-weighting curve which is a psychoacoustic equal loudness curve. Thanks to this, you will hear the same loud noise for all the frequencies. It’s similar to white noise, except for it doesn’t have equal power for each frequency.

grey noise image

This noise is more intense for high and low frequencies, and less intense for middle-range frequencies (audible to human ear) which is what gives you the feel that it sounds the same for all frequencies. People use grey noise to test hearing too, more specifically to understand how does it differ from average human hearing.

Listen to it, it has a mild and pleasant vibe going on, unlike the screeching violet noise.

Now you know that you can not only hear the noise but visualize its colors as well.

 

Before you go, let’s see if you can guess what color of noise this is:

Leave your answers in the comments!