The Stuff of Sensations

With the senses of sight and hearing, a person can see colour and hear sound, respectively. So many hues and timbres exist, yet both are composed of basic elements and can be constructed by combining them in special ways.

Colour

• Sensing body part: Eyes. The lens and cornea focus light to fall on a surface of rods and cones, the pattern of which is sent to the brain as electrical impulses.
• Element: Primary colour
• Medium: Colourants (usually ink) on a white surface, or light on a black surface
• Types of element: For colourants, cyan (reflected blue and green light), magenta (reflected red and blue light) and yellow (reflected green and red light) (practical implementations also use black), although the fine arts has traditionally used blue, red and yellow (which alone cannot theoretically produce black). For light, red (long-wavelength visible light), green (mid-wavelength visible light) and blue (short-wavelength visible light).
• Combining method: For colourants, subtractive colour mixing. For light, additive colour mixing.
• Common applications: Fine arts, printing, computer displays

This closeup of a newspaper print shows cyan, magenta and yellow inks' forming an image. Their relative concentrations determines the perceived colour.

Sound

• Sensing body part: Ears. The ear canal concentrates sound waves which stimulate the eardrum and ossicles. The cochlea sends the detected vibrations to the brain as electrical impulses.
• Element: Sine wave
• Medium: Compression waves over air
• Types of element: Sine and cosine waves of varying amplitudes and wavelengths. Note that a cosine wave is a sine wave that is shifted 90° ahead.
• Combining method: Fourier synthesis
• Common applications: Music synthesisers (synths), voice modulation, equalisation (EQ) filters

A sawtooth wave can be constructed under Fourier synthesis by combining an infinite number of sine waves.