Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!linus!decvax!decwrl!glacier!oliveb!hplabs!hao!seismo!rochester!rocksanne!sunybcs!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: net.med,net.sci
Subject: Re: Fingernails and Chalkboards
Message-ID: <930@kitty.UUCP>
Date: Sun, 30-Mar-86 21:53:58 EST
Article-I.D.: kitty.930
Posted: Sun Mar 30 21:53:58 1986
Date-Received: Wed, 2-Apr-86 08:23:37 EST
References: <1108@mit-bug.UUCP>
Organization: Recognition Research Corp., Clarence, NY
Lines: 22
Xref: linus net.med:3527 net.sci:399
Summary: A lot of ultrasonic energy

In article <1108@mit-bug.UUCP>, jeff@mit-bug.UUCP (Jeff Rodriguez) writes:
>      Why do most people get chills all over their bodies when
> they hear the sound of fingernails scraping down a chalkboard?
> Of course, the same reaction can be caused by other similar sounds,
> as well.  It just doesn't make much sense.  Any ideas?

	I was once curious about that very same topic.  Although I never
went to the trouble of getting a definitive answer (like searching the
literature, or asking a neurophysiologist), I did conduct an interesting
experiment:  I connected a condenser microphone to a Genrad realtime
audio spectrum analyzer, and performed the above maneuver several times.
I was amazed to find an exceptionally large amount of energy in the
10 kHz to 40 kHz region.  I would surmise that a person's "reaction" results
from this sound with many high frequency components, and comparatively few
low frequency components - this being not a common type of sound.

==>  Larry Lippman @ Recognition Research Corp., Clarence, New York
==>  UUCP    {decvax|dual|rocksanne|rocksvax|watmath}!sunybcs!kitty!larry
==>  VOICE   716/688-1231                {rice|shell}!baylor!/
==>  FAX     716/741-9635 {G1, G2, G3 modes}    duke!ethos!/
==>                                               seismo!/
==>  "Have you hugged your cat today?"           ihnp4!/