SOUND & LIGHT (COLOUR)

Is there a relationship between sound and light?
You would not be the first to ask this question, in fact, this question was put "on the table" by some of great composers in the past, such as Hector Berlioz, Claude Debussy, Richard Wagner, Alexander Nikolayevich Scriabin, Nikolai Rimsky-Korsakov, and others. 
In this blog I will share some information about the relationship between Sound and Colour from various sources. The text quoted and images used belong to the authors I quote. I have provided links to their web sites, where you can find a lot more interesting information about this and other subjects.

ALEXANDER NIKOLAYEVICH SCRIABIN
Alexander Nikolayevich Scriabin was a Russian composer and pianist. Though Scriabin's late works are often considered to be influenced by synesthesia, a condition wherein one experiences sensation in one sense in response to stimulus in another. His colour system, unlike most synesthetic experience, accords with the circle of fifths: it was a thought-out system based on Sir Isaac Newton's Opticks.
Note that Scriabin did not, for his theory, recognize a difference between a major and a minor tonality of the same name.

In his autobiographical Recollections, Sergei Rachmaninoff recorded a conversation he had had with Scriabin and Nikolai Rimsky-Korsakov about Scriabin's association of colour and music. Rachmaninoff was surprised to find that Rimsky-Korsakov agreed with Scriabin on associations of musical keys with colors; himself skeptical, Rachmaninoff made the obvious objection that the two composers did not always agree on the colours involved. Both maintained that the key of D major was golden-brown; but Scriabin linked E-flat major with red-purple, while Rimsky-Korsakov favored blue.
(Source: Wikipedia)

So, how exactly can we compare and relate sound and light / colour?

WHAT DO SOUND AND LIGHT HAVE IN COMMON?

• Sound and light both exhibit oscillatory wavelike characteristics with various frequencies, wavelengths, and amplitudes.
• Both propagate at a finite speed.
• Both exhibit Doppler shifts toward higher frequencies when the source of the wave is approaching us.
• The sensed intensity is dependent on the amplitude of the wave.
  

WHAT IS THE DIFFERENCE BETWEEN SOUND AND LIGHT?

• The frequencies of visible light and audible sound differ from each other by more than ten orders of magnitude. Audible acoustic range: roughly 20 Hz to 20,000 Hz vs. visible optical range: roughly 380 trillion Hz to 760 trillion Hz.
• Light waves are composed of transverse waves in an electromagnetic field, while sound waves are mechanical longitudinal waves (alternate compression and expansion of matter).
• Sound requires a "medium" to propagate, light does not. Therefor while light does propagate through a vacuum (absence of a medium), sound does not.
• The denser the medium, the greater the speed of sound. The opposite is true of light.
• The speed of light in a medium is constant. The velocity of sound waves can change.
• Electromagnetic waves, including light is a "stream of particles" (photons). Sound does not consist out of particles.
• Light waves can be polarized, but sound waves cannot.

It’s also worth noting that while the frequency range of audible sound covers a factor of 1000, (about 10 octaves), the range of visible light covers only a factor of 2 (just one octave).

SENSATION OF SOUND AND COLOUR AND THEIR "DIMENSIONS"

"If our ears contained just a few individual sensing elements, each tuned to one particular absolute frequency, we might all be able to recognize the absolute “color” of audible tones just as well as we can recognize absolute red. However, the ear needs to respond over a much larger range of frequencies, and the dimensionality of the “space” of audible sensation is much greater, we can distinguish a much greater variety of spectral characteristics of sound than we can of light.

Roughly speaking, the coiled cochlea of the human ear has a varying elasticity along its length, so it can be regarded as a series of oscillators of different resonant frequencies, and these perform a fairly detailed spectral analysis of incoming sound waves, transmitting to the brain something a 3000 point spectral profile. The detailed mechanics of how the cochlea responds to stimuli are very complicated, and the study of this function is hampered by the fact that the mechanical properties change significantly if a cochlea is removed for study. Nevertheless, it seems clear that whereas the spectral analysis of optical stimuli has only three dimensions, the spectral analysis of aural stimuli has at least 3000 dimensions. It is not surprising that we (most of us) don’t memorize the absolute sensations associated with tones over ten octaves."  

(Source: www.mathpages.com)

Nick Anthony Fiorenza writes at his website www.lunarplanner.com:

"The octave of visible light, extending from the color red to the color violet, is forty octaves higher than the middle audio octave, that which you would hear on a piano keyboard. Light, however, is measured by its wavelength, whereas sound in measured by its frequency."

"Waves of light are quite short. For example, the center frequency of the color green has a wavelength that is 0.0000005132 meters long (0.5132 x 10-6meters). To make this easy, we measure visible light in a unit called the Ångstrom (Å) (that is a capital A with a little circle on top). One Ångstrom = 1 x 10-10 meters (that is 0.1 nanometers). The colors of the visible spectrum are measured in thousands of Ångstroms. As show in the following chart, the visible spectrum of light extends from about 7000 Å (red) to about 4000 Å (violet). Also shown in the chart are the center wavelengths for each of the seven basic colors; their corresponding audio frequencies; and the location of the musical notes of an audio octave translated to the the visible spectrum."

"Thus, when we raise each note in middle audio octave by forty octaves we find its corresponding color harmonic. As shown in the chart below, the note "G" lies in the red area of the color spectrum. The note "A" raised forty octaves lies in the orange part of the spectrum. The note "B" lies in the lemon (yellow-green) part of the spectrum. The note "C" in the green band; the note "D" in the turquoise-blue band; and the note "E" lies in the violet band. Notice that the note "F" lies in the far violet area of the visible spectrum. This is near where the human eye range of color perception begins to drop off (although unique to each person). Also notice that the note F# lies even further from violet, in the near-UV (ultra-violet) area of the spectrum. Thus (when raised 39 octaves rather than forty octaves), it also it resides in the far-red (or near infra-red). Because of this, the note F# embraces the visible spectrum, and thus has some red and some violet, a combination that produces more of a purple color."

INTERFERENCE: A Grand Scientific Musical Theory (by Richard Merrick)
Source: www.interferencetheory.com
Excerpt from "Synesthetic Coupling"

"There have been many attempts through history to establish an association between color and pitch, though none have been universally accepted. Composers like Berlioz, Debussy, Wagner and Scriabin all had ideas about which colors matched which tones. The Rosicrucian Order developed their own color mapping and even Charles Fourier suggested in his 1846 Theorie de l’Unite Universelle an alchemical connection between certain pitches, colors and metals. One of the more recent proposals suggests that we should reduce light frequencies down to the speed of sound in order to produce a color mapping. While this last theory is a reasonable approach, physicists would argue against this, pointing out that that sound and light waves are not the same kind of energy. Science requires some other causal link or coupling." 

"Rather than use any of the above methods, we will construct our synesthetic model from Isaac Newton’s popular 12-step tertiary color wheel containing three primary colors, three secondary colors and six tertiary colors. Taken as two groups of six colors, the even group of primary and secondary colors can mix adjacently to produce an odd group of tertiary colors in much the same way as one wholetone scale mixes to the other. This suggests coherent light is perceived to mix harmonically just like coherent sound mixes into music harmony. This is without a doubt due to the fact that the visible light spectrum frequency doubles to form an octave of light just like an octave of sound." 

"Since the visible color spectrum ranges from about 375 terahertz on the low end to about 750 terahertz on the high end, the visible color spectrum naturally forms a 2:1 octave doubling of light frequencies like that of a musical octave. From this, we can proportionally map twelve colors to twelve tones by starting just below human visibility at 370 terahertz and then calculating twelve color frequencies by multiplying each preceding color by 2^(1/12), making sure to balance around the center of the visible spectrum. Doing this creates a logarithmic color scale that perfectly matches an equal-tempered musical octave. It also places each color within its corresponding spectral color band for the three cone photoreceptors on the retina of the human eye." 

THE ROSICRUCIAN ORDERThe Rosicrucian Order based their theories on Just intonation and suggest that note names, frequencies, and colours should be:

Note

C

C#

D

D#

E

F

F#

G

G#

A

A#

B

Colour

Yellow- Green

Green

Green- Blue

Blue

Blue- Violet

Violet

Violet- Red

Deep Red

Red

Red- Orange

Orange

Yellow

Hertz

256

288

320

341

384

426

480

THREE CENTURIES of COLOR SCALES image by Fred Collopy (www.rhythmiclight.com)

REFERENCES:

• Nick Anthony Fiorenza (www.lunarplanner.com)
• INTERFERENCE: A Grand Scientific Musical Theory by Richard Merrick
  
• Fred Collopy (www.rhythmiclight.com)
• www.mathpages.com
• www.wikipedia.com
• www.musicalcolors.com