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1 .This is Scientific American 60-Second Science. I'm Karen Hopkin. This'll just take a minute.
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2 .Got your attention? Thought so.
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3 .But what is it about a piercing shriek that really turns our heads?
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4 .It's what it does to our brains.
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5 .The acoustical properties of the human scream poke at the neural circuits that control fear.
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6 .That's according to a study in the journal Current Biology.
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7 .Our every waking moment is filled with noise, from planes flying overhead to various creatures scrambling underfoot.
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8 .But a heartfelt cry can cut through all that.
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9 .So what's so special about the sound of a screech?
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10 .To find out, researchers prepared a sampler of screams from YouTube videos, popular films and excited volunteers.
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11 .If that screech sounded familiar, that's because it's the famous Wilhelm Scream, a stock sound effect heard in everything from Bugs Bunny to Star Wars.
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12 .The scientists analyzed the acoustical characteristics of the various screams.
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13 .And they found these alarming sounds are not only loud, they're particularly rough.
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14 .That is, they rapidly change in frequency.
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15 .Normal speech is relatively smooth, with frequencies ranging only between four and five Hertz, or cycles per second.
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16 .But a shriek can swiftly fluctuate between 30 and 150 Hertz——a range that can make your hair stand on end.
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17 .When the researchers asked people to rate how frightening screams were, they found that more roughness meant more terrifying.
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18 .And increasing roughness of the sound corresponded to greater activation of the fear center of the brain.
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19 .Only one other noise scored as high as screams in terms of roughness .
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20 .Which, ironically, is enough to make you.
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21 .Thanks for the minute, for Scientific American 60-Second Science. I'm Karen Hopkin.
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