- [Woman Filming] Doesn't
that gross you out?
(nails squealing)
- Aarghh!
- Aahh! Few noises are
as terrible as that one.
- Let's explore why we
humans detest it so.
(upbeat techno theme music)
- [Woman] Nails dragging
across a chalkboard
can make your spine tingle
and your hair stand on end.
And much of that has to do
with both the frequency range
of the sound, and the
shape of the ear canal.
- [Man] The human ear
canal amplifies frequencies
in the 2,000 to 4,000 Hertz range.
And the acoustic structure
of that scraping noise
on a chalkboard just
happens to be concentrated
within that range, ricocheting
around your ear canal
like a pinball.
- [Woman] Sukhbinder
Kumar, a neuroscientist
at Newcastle University
Medical School in the UK,
and his colleagues, wanted to find out
what the emotional landscape
of the grating noise
looked like in the brain.
So, they recruited 13 healthy volunteers,
who underwent functional
magnetic resonance imaging
while listening to 74 sounds,
including the old nail-scraping one,
rating them on a scale of
one, "least unpleasant,"
to five, "most unpleasant."
- [Man] Researchers witnessed
how the auditory part
of the brain, which perceives sound,
interacts with the amygdala,
which processes emotion.
And they found that the
more unpleasant the sound,
the more the amygdala engages
and causes the auditory complex
to heighten its response.
- [Woman] And when that happens,
we become more physiologically alert.
Hence the spine-tingles,
and the slapping of hands
over the ears, as we
recoil from the commotion.
- [Man] Besides the sound being
amplified in the ear canal,
why else would we humans be so bothered?
Some have theorized that because
the chalkboard-scratching
shares the same mid-range frequencies
of primate warning calls,
our response is a kind
of evolutionary hangover.
That we can't help but
overreact, since on some level,
we're misattributing it
to some sort of predator
about to pounce on us or our younglings.
- [Woman] But this has
since been disproved.
The answer may be that
all that gritting of teeth
could be, in part, psychological.
- [Man] Musicologists Michael
Oeler and Christoph Reuter
asked volunteers to listen
to various sound samples,
including the rubbing of
styrofoam, plates scraping,
and nails on a chalkboard.
Half were told exactly what
was producing the sound,
while the other half were told
that the sounds were part of
a contemporary musical piece.
- [Woman] The volunteers rated
the clips from best to worst,
and all the while, indicators
of stress were monitored,
like heart rate, blood pressure,
and electrical conductivity of skin,
AKA "the stress sweats."
- [Man] All the participants who heard
the unpleasant frequencies
had a physiological response:
elevated heart rate and
increased perspiration.
But those who weren't told
the source of the sounds,
reported being less disturbed by it,
leading the researchers to wonder
if priming plays a part in
increasing our reaction.
- [Woman] And it turns out
there are far more offensive
noises than just dragging
your nails on a chalkboard.
In a 2008 Newcastle University
study, 50 participants
listening to 75 sounds
rated nails on a chalkboard
the 5th most irritating sound,
behind a knife scraping
against a metal bottle,
fork tines running across a glass,
and actual chalk on a chalkboard.
- Thankfully, most schools
don't even use chalkboards
anymore, but does that
mean the new despised sound
is gonna be markers on a whiteboard?
- (mimics squeaking marker)
Let us know what sound drives you crazy.
For me personally, it's
the balloons, that noise.
Aah! Let us know in the comments below.
And to keep the videos coming,
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