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Re: brightness

Chen-Gia Tsai wrote:
> I am interested in analogues between visual and auditory processing.
> We describe sounds rich in high-frequency harmonics "bright". This adjective
> is apparently universal. Why do we use such a visual concept to describe an
> auditory feature?


Here's an idea. For whatever reasons, we seem to associate high
frequencies with physical height, perhaps because high frequencies
travel in straight lines and they tend to transmit at some height
whereas low frequencies can creep and crawl over terrain. Or maybe
because a lot of birds make high pitches but big animals that hug
the ground make low pitches. Now, the sun is also high and very
bright, and we look up to see the sun. So we look up to see the
sun and we point our ears up to hear high frequencies, and thus
we may associate height with increased brightness, and thus high
frequencies with increased brightness. If there are a lot of
strong high frequencies in a sound, we will hear "higher" and
thus it will sound brighter.

This is just a conjecture; there's nothing rigorous about it.

Several researchers have found the spectral centroid, which
correlates strongly with "brightness" or "sharpness" verbal
attributes, to be an important, perhaps the most important,
single characteristic for distinguishing amongst sound spectra.

See for example,

von Bismark, G. (1974). "Sharpness as an attribute of the timbre
of steady sounds", Acustica, 30(3), pp. 159-172.

Jim Beauchamp
University of Illinois at Urbana-Champaign