Memtropy Signals from the Noise

June 8, 2008

The Sounds of Colour

Filed under: Physical Universe,Thoughts — Tomek @ 6:48 pm

A440 is the 440 Hz tone that serves as the standard for musical pitch. A440 is the musical note A above middle C (A4).

Every time you double the frequency, the pitch goes one octave up. Starting from the note A at 440Hz, doubling the frequency six times, you hear five different As until the sound becomes ultrasonic and inaudible. Another 36 octaves up and the frequency is the same as that of visible light, in our case from A440 you get a frequency of 484THz, which is a wavelength of 619nm, which is red.

The frequency spectrum of visible light is a bit less than one octave. This can actually be seen, in that on one end of the spectrum is red and the other end is moving back from blue to red, giving violet.

Below is the best annotated picture of the visible part of the electromagnetic spectrum I could find. It does have its limitations, compared to the picture of the rainbow above, yellow and cyan are not clearly visible.

The corresponding colours to the different notes

Note/Pitch f/Hz transposed 40 octaves f/Hz corresponding λ/nm
G4 392.00 G44 431008558088192 696
G#4 415.30 G#44 456627179015372 657
A4 440.00 A44 483785116221440 619
A#4 466.16 A#44 512548340404060 585
B4 493.88 B44 543026802726010 552
C5 523.25 C45 575319459233792 521
C#5 554.37 C#45 609536261090181 492
D5 587.33 D45 645776164341678 464
D#5 622.25 D#45 684171110383616 438
E5 659.26 E45 724864035727605 414
F5 698.46 F45 767964891536424 390

Sound is not light, and I used the speed of light to calculate the corresponding wavelength of the visible light. Using the speed of sound would give the right wavelength and a higher frequency, the same notes but transposed up.

    Other interesting notes:

  • FM radio: E32-G32
  • Microwave oven, WLAN (2.45GHz): D27

For reference, the absorbance of the different human photoreceptor proteins against the light’s wavelenth:

Although sound cannot be seen by most people (some do, see below), it is certainly interesting to consider to view the electromagnetic spectrum like a musician would view the soundscape. To me the note C (green) played on a piano sounds friendly, D (blue) sounds moody and an A (red) sounds somewhat alert and open. More research comparing mixed colours and musical accords would be interesting to hear/see.

Synaesthesia:

Which figure would you name Booba, which Kiki:

If you are like 95-98% of humans, regardless of language, the one on the left is Kiki and on the right is Booba. This is a good example for the intuitive mixing of senses happening. But it is estimated that up to 5% of the population also have other forms of synaesthesia, so for example for them, sounds or numbers or letters have colours.

Neurologist V. S. Ramachandran talked about that at TED (watch from minute 18:00, you want to skip the journey to the center of your mind):

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