Blackboard scratching, a scraping fork on porcelain,
brake squealing and similar squealing noises are perceived mostly
as particularly unpleasant because, in addition to a recognizable
fundamental pitch in the spectrum, they have strong energy components
in the 2000-4000 Hz range. The human auditory system is particularly
sensitive in this range, since this is where the self-resonance
of the outer ear canal lies. After removing the fundamental pitch
and/or the range between 2000-4000 Hz from the spectrum, the unpleasant
sounds are already judged to be much more pleasant.
Listen here to the examples of the 2011 study in
which listeners rated the unpleasantness of blackboard scratching
and chalk noises (Y-axis, the higher the value, the more unpleasant)
spectrally manipulated in different ways (X-axis).
Listen here to the examples of the extended 2012
study in which listeners rated the unpleasantness of blackboard
scratching, styrofoam, vomit, and squeaky instrumental sounds (Y-axis,
the higher the value, the more unpleasant) spectrally manipulated
in various ways (X-axis).
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