Sound in all its many colours

Education, Featured — By on November 23, 2012 09:38

While catching up on the latest tech news over breakfast, I was drawn to this Wired article about research into white smells which references another Wired article, from April 2011, about how sound is separated into different colours, including white, pink, brown, blue, violet and grey.

I learned that the colour of a sound is governed by its spectral density; “the way the power that the signal contains is distributed over different frequencies”.

White noise has equal energy per cycle, so its frequency spectrum is completely flat. It cuts through background noise, and is used in the making of sound masking tools for tinnitus sufferers.

Pink noise’s spectrum falls off logarithmically over time, with equal power in bands that are proportionally wide. It matches the capabilities of the human ear and is used for amplifier and loudspeaker testing.

Red and brown(ian) noise are the same thing; a low roar used in climatology to describe climate regime shifts.

Blue and violet noise change proportionally with increasing frequency. Retinal cells are arranged in a blue noise pattern, which studies show yields good visual perception. Violet noise, which is also used to treat tinnitus, has a power density that increases per octave with increasing frequency over a finite frequency range.

Grey noise contains both higher and lower frequencies at the same time. It has lots of power at the top and bottom end of the frequency spectrum but very little centred around the range of normal human hearing. It’s used in the study of hearing difficulties.

Then there’s black noise, orange noise and green noise. Have you encountered any other colours in your audio industry travels?




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