(US navy jet breaking the sound barrier - the white halo is formed by condensed water droplets thought to result from a drop in air pressure around the aircraft)
Do we Hear in ‘colour’?
In this post I am not referring to Synesthesia (from the Greek roots syn, meaning "together," and aisthesis, or "perception") is a condition in which otherwise normal people experience the blending of two or more senses.
What I am referring to is that Individuals rarely agree on what ‘colour’ a given sound might be. Composers Liszt and Rimsky-Korsakov famously disagreed on the colours of music keys.
It is interesting that sound waves that reach our ear have a history. For qualities of a sound reaching the ear depend not only upon the sound source to which one is listening, but also upon the properties of the materials and surfaces sound encounters on its way to the ear. Natural sounds such as speech and music are comprised of many frequencies, some low pitched, some high pitched, and some in between. For example, peaks and valleys in energy across frequencies are used to distinguish speech sounds.
However, as sound waves travel through the environment to your ear, the relative amounts of energy at different frequencies is virtually always ‘coloured’ by the surroundings. Sound energy at some frequencies is reinforced by reflective properties of surfaces, while energy at other frequencies is dampened by acoustic absorbent materials and shapes of objects in the environment. The challenge for listeners is to perceive the true sound source without mistaking effects of surroundings as qualities of the sound to which one is listening.
This challenge for hearing bears close resemblance to the problem of colour constancy in vision. Perceived colours of objects depend upon relative amounts of different wavelengths of light reflecting off objects.
For example, we perceive short wavelengths as blue and long wavelengths as red, and all colours are combinations of energy at different wavelengths varying from short to long. These combinations are called spectral distributions. The spectral distribution of light entering the eye depends on the type of illumination in addition to reflective qualities of surfaces light encounters on its way to the eyes. For example, sunlight, incandescent light, and fluorescent light produce dramatically different patterns of wavelengths reflected off the same object. Nevertheless, observers see objects as having pretty much the same colours whether viewing them indoors or outdoors across different illuminations. This fact of vision is called "colour constancy."
Research done on whether people have the auditory equivalent of visual colour constancy when listening to speech sounds provide evidence that the auditory system is quite adept at factoring out reliable characteristics of a listening environment. The findings are that auditory system of ‘auditory colour’ bears a striking similarity to the phenomenon of visual colour constancy. It would appear that synesthetes show the same trends as non-synesthetes do. For example, both groups say that loud tones are brighter than soft tones, and that lower tones are darker than higher tones
For a more detaiedl view see: Source: http://www.acoustics.org/press/146th/Kluender.htm
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