White noise - or silence?
Homage to R.Murray Schafer
We generally speak about "white light", but this is inadequate, since what we mean is colourless, achromatic, neutral light. Such light is not white, but rather just invisible.
WHITE is an attribute of illuminated objects: The snow is white, clouds are white; there are beautiful white flower petals, feathers and stones. Goethe (in the Chemical Colours chapter of his Farbenlehre) points out that if clear, transparent glass is crushed, it is thereby transformed into a fine white powder. In a microscope the particles are still transparent. But, as he puts it, the dynamic connection between them is broken; the unitary piece of glass has turned into a mere conglomerate. (The same is true of the water drops that make up a white cloud.) This says something about what "white" is. "The principle of whiteness", so to speak.
When physicists, after Newton, speak of white light they mean radiation with constant energy irrespective of wavelength (within the visible range of wavelengths), or, alternatively, the same density of photons at various frequencies in a beam of light. The flux is just indifferent as to measurement of frequency. Lord Rayleigh defined white light as "a completely random process". In view of this, thermal radiation, at about 6500K, is often taken as a physical definition of "neutral light".
The equal photon density spectrum of white light can be modified into "yellow light", by attenuating the relative amount of high frequency photons; or "blue light" by attenuating the low frequency part. That is to say, so it looks if the modified light is seen side by side with the neutral light one started from. Stronger attenuation leads to "red" and "violet" respectively.
In accordance with this optical (rather technological) analogy, electro-acoustic composers speak of "white noise", referring to a sound generated by a random process. A sound, not represented by any particular frequency or limited range of frequencies. This "white noise" can be "coloured" by shaping the frequency spectrum in various ways. For instance, if high frequences are slightly attenuated, "pink noise" is obtained. But listen:
Do these sounds really in any way resemble colour qualities, as "white" and "rose" ? They are just noisy! Nor could white and rose reasonably be characterized as particularly "noisy" colours. Maybe "pink noise" could be synaesthetically characterized as "darker" than "white noise". And red is darker than white. So far the analogy holds. But to carry it further leads us astray.
At the bottom of the problem lies the deceptive terminology: White light isn't white. It is rather invisible and consequently should correspond to something inaudible!
So, let us change perspective and look at the issue from another point of view - a more phenomenological point of view, if you like.
SILENCE is a necessary condition for the perception of tones and their timbre in the same way as LIGHT is a necessary condition for the perception of object colours, such as white, blue, yellow, pink etc. The painter starts with a white canvas, as his "tabulae rasa", on which to bring forth a work of art. Analogously the musician starts from silence when performing a subtle piece of music.
LIGHT, conceived as a general condition for sight, is invisibly present. It is a neutral, or indifferent, state - like the painter's white canvas, or the silent room of the musical performer. Likewise, from the aocoustical point of view, sound events are tiny modulations of pressure in a volume of air of constant pressure, i.e. a balanced, neutral state of the medium. Thus the term "neutral light" is the adequate one to designate what we conventionally call "white light".
This rhymes with what Kandiskys' writes, in "Über das Geistige in der Kunst", concerning white: "Weiss wirkt auf unsere Psyche als ein grosses Schweigen ... Es ist ein Schweigen, welches nicht tot ist, sondern voll Möglichkeiten... Es klingt innerlich wie ein Nichtklang, was manchen Pausen in der Musik ziemlich entspricht ..." (White acts on our Psyche as an overwhelming muteness - a muteness however that is not dead, but full of possibilities ... like the rests in a piece of music... )
In conclusion: We should rather speak of "white silence" than of "white noise".
© Pehr Sällström, 2006
To be found at http://pscolour.eu/English/white.htm