Naked Science Forum

General Science => General Science => Topic started by: paul.fr on 07/08/2007 22:54:31

Title: Why does chalk squeak on a blackboard?
Post by: paul.fr on 07/08/2007 22:54:31
One of the things i don't miss about school, is the noise made by the teacher whilst using the chalk. But why does it make such a terrible noise?

Aslo, changing the angle of the chalk produces different pitches, why is that?
Title: Re: Why does chalk squeak on a blackboard?
Post by: lightarrow on 08/08/2007 19:19:58
Quote from: paul.fr on 07/08/2007 22:54:31
One of the things i don't miss about school, is the noise made by the teacher whilst using the chalk. But why does it make such a terrible noise?

Aslo, changing the angle of the chalk produces different pitches, why is that?
It should be because of the high frequency vibrations produced by the chalk accelerating/stopping many times every second on the board, because of friction. The amplitude and frequency of those vibrations depend on many factors: mass, consistence, shape, dimensions, angle, of the chalk (at constant properties of the board).
Title: Re: Why does chalk squeak on a blackboard?
Post by: kdlynn on 08/08/2007 20:07:03
i always liked the chalk noise. didn't like the fingernails on a chalk board noise.. but the chalk was ok
Title: Re: Why does chalk squeak on a blackboard?
Post by: lightarrow on 08/08/2007 21:04:51
Quote from: kdlynn on 08/08/2007 20:07:03
i always liked the chalk noise. didn't like the fingernails on a chalk board noise.. but the chalk was ok
But I assume paul.fr intended that horrible, high-pitched whiz it makes sometimes when the chalk is still long.
Title: Re: Why does chalk squeak on a blackboard?
Post by: paul.fr on 08/08/2007 21:41:11
Quote from: lightarrow on 08/08/2007 21:04:51
Quote from: kdlynn on 08/08/2007 20:07:03
i always liked the chalk noise. didn't like the fingernails on a chalk board noise.. but the chalk was ok
But I assume paul.fr intended that horrible, high-pitched whiz it makes sometimes when the chalk is still long.

You assumptions, are correct. [;D]
Title: Re: Why does chalk squeak on a blackboard?
Post by: kdlynn on 08/08/2007 23:07:32
oh i see.
Title: Re: Why does chalk squeak on a blackboard?
Post by: _Stefan_ on 09/08/2007 07:24:18
Every time I read the topic heading of this thread I get shivers down my spine. I hate the screech of chalk and fingernails on blackboards!
Title: Re: Why does chalk squeak on a blackboard?
Post by: dentstudent on 09/08/2007 07:28:24
Strangely, this noise doesn't bother me at all. What I don't like is the sensation of drying a wooden spoon on a teatowel. It makes me clench my cheeks just thinking of it! Also, that accidental grinding of your teeth that squeaks.
Title: Re: Why does chalk squeak on a blackboard?
Post by: kdlynn on 09/08/2007 07:52:21
i don't like the sound of terra cota pots rubbing together. or touching them... or spelling the name right....
Title: Re: Why does chalk squeak on a blackboard?
Post by: Monox D. I-Fly on 16/10/2019 07:42:54
Quote from: kdlynn on 08/08/2007 20:07:03
i always liked the chalk noise. didn't like the fingernails on a chalk board noise.. but the chalk was ok
Ugh... Even imagining that feels hurt.
Title: Re: Why does chalk squeak on a blackboard?
Post by: chris on 13/10/2020 10:23:45
We answered a very similar question recently, which will be useful insight for people following this thread: https://www.thenakedscientists.com/forum/index.php?topic=80434.0
Title: Re: Why does chalk squeak on a blackboard?
Post by: Colin2B on 16/10/2020 17:30:07
Finally managed to get these to upload.
@chris  - When you get invited to dine with the queen, make sure you read the one about fork squeal before you go


* squeals2010june-pdf.PDF (454.95 kB - downloaded 566 times)
Title: Re: Why does chalk squeak on a blackboard?
Post by: Colin2B on 16/10/2020 17:31:14
And this is the fork one
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