Q & A: Sound Waves vs. Light Waves

i heard this from a friend, color has sound. from what i think i understand ,if matter is condensed vibration and pigments have different weights ,the intensity of vibration in each pigment would cause a certain tone . i need clarification thanks.
- matt (age 22)
hudson valley c.c., albany

Matt -
The key background to this question is the nature of sound
waves and light waves. You’re right in that sound waves are a
vibration traveling through an object, including "condensed" things
like solids and liquids. In solids, those waves can consist of either
alternating compressed and stretched regions, or regions wiggling
sideways, compared to the direction the wave is traveling. Light is
a wave of oscillating electric and magnetic fields perpendicular to
the direction it’s going. Light can travel fine through a vacuum,
which can have fields in it, but there can’t be sound in a vacuum
because there’s no stuff there to oscillate.

Audible sound has frequencies that cover a very big range,
from about 20 Hz to 20,000 Hz, meaning that the pressure at your ear
oscillates back and forth 20 to 20,000 times per second. Each
frequency gives a different audible pitch. Visible light has
frequencies from around 4*10^14 Hz to around 8*10^14 Hz. Each
frequency gives a slightly different visible color. Not only are the
light frequencies much higher, but the highest one is only about
twice the lowest one. The sound frequencies are much lower, and the
highest one is a thousand times higher than the lowest one. So you
can see that there’s no direct match between the sound and light
oscillations.

If you are wondering what effect the pigments (light
absorbers) in a material have on the type of sounds that come from
it, the answer is usually: not much. There’s not much connection
between the frequencies of light some pigment absorbs and the
frequencies of audible sound it might absorb or emit. The color of a
pigment also is really unconnected with the density or rigidity of
the molecules, which affect how sound travels. Lots of different
common pigments are organic compounds with densities not too far from
1 gram/cm^3, yet these provide a whole array of different colors.


On a different note. Musicians often refer to sound as
having color. This refers to a different concept than the color that
pigments give. When you overlap various pure tones of sound, the
overall effect is a sound that is slightly different in how it sounds
but has the same fundamental tone. For example, a trumpet sounds
vastly different than a flute, but the can both be playing the exact
same note. The difference (or color) comes from higher frequencies
(called harmonics) that the instrument itself adds to the fundamental
tone.


Adam & Mike

(published on 10/22/2007)

Hello! I respectfully disagree and propose the following hypothesis... If you measure the frequency of Middle-A, you will hear sound at 220 Hz. Hearing the A one octave up, will yield a frequency of double the previous octave, therefore 440 Hz. So we can safely say that you get the entire range of an octave between X and 2X where the X equals the frequency. Now let's look at the lowest frequency of light in the so-called visible spectrum (~400 THz), which is a deep, dark red. Compared to the highest frequency of light in the visible spectrum (~800 THz), which borders on Ultra-Violet, we see another X to 2X range! I propose that in this manner, any music can be represented in colour and I suspect that this is how musical cervants are able to "see music in colour". This includes people who claim to sing a particular note accurately on demand without hearing a note of reference beforehand. Regards, Heliac
- Anonymous

You've taken one particular audible octave and showed that there's a simple mathematical map between it and the visible frequency range.  How do you represent the other 9 octaves or so that we can hear?

Here's another question: are there any studies of any kind showing that the mental sense associating sounds and color actually fits the particular map you've mentioned?

Mike W.

(published on 09/01/09)

It is true that sound and light are alike only to the extent that they are both waves. They are inherently different on the basis that light is electromagnetic radiation. It requires no medium and can therefore can propagate through both extremely sparse - space, upper atmosphere - and extremely dense - plastics, water - environments. Sound however, requires sufficient medium. It is required to have the interaction of molecules of the medium with other molecules of the medium. This is why, upon interrupting the medium with dense objects like foam, the interaction of molecules on one side of the interrupter can not transfer to those on the other side of the interrupter and can even be absorbed by the interrupter. One might say that light can be blocked as well, and they would be right. A leaf of an oak tree does absorb light and reflect light. Forests are darker than standing on a rooftop on a cloudless day. But the propagation of sound being in a medium of air, means that it relies on its own medium to transmit its propagation to somewhere else. Because light does not have a medium, it can transmit through objects in a way that sound cannot. SOUND REQUIRES MEDIUM.
- Wilson (age 19)
Charlotte, NC

What you say is true.

Mike W.

(published on 01/25/11)