The Naked Scientists

The Naked Scientists Forum

Author Topic: Cello vibrations and how a violin bow works - Garage Science  (Read 21054 times)

Offline thedoc

  • Forum Admin
  • Administrator
  • Sr. Member
  • *****
  • Posts: 511
  • Thanked: 12 times
    • View Profile
For this week's kitchen science I took some high speed footage of some cello strings but there were some fascinating effects which didn't really fit into the kitchen science, so I thought I would post them here.

 Read more about this experiment.


Garage science is a blog of science experiments you probably can't or shouldn't do at home


 
« Last Edit: 13/07/2010 14:44:25 by _system »


 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8134
  • Thanked: 53 times
    • View Profile
Cello vibrations and how a violin bow works - Garage Science
« Reply #1 on: 09/03/2009 12:35:42 »
If you don't mind getting flour/talc on your cello you could try to obtain Chladni patterns...



http://en.wikipedia.org/wiki/File:Chladni_guitar.png

http://en.wikipedia.org/wiki/Ernst_Chladni#Chladni_plates
« Last Edit: 09/03/2009 12:37:39 by RD »
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Cello vibrations and how a violin bow works - Garage Science
« Reply #2 on: 10/03/2009 05:01:46 »
Neat little new Board you've got here. :)
 

Offline daveshorts

  • Neilep Level Member
  • ******
  • Posts: 2583
  • Physics, Experiments
    • View Profile
    • http://www.chaosscience.org.uk
Cello vibrations and how a violin bow works - Garage Science
« Reply #3 on: 11/03/2009 13:21:52 »
I had a go at looking for the chaladni patterns directly with the high speed camera but I think the movements were far too small to be visible. My housemate who owns the cello wouldn't be keen on covering it with sand...
 

Offline BenV

  • Neilep Level Member
  • ******
  • Posts: 1503
    • View Profile
Cello vibrations and how a violin bow works - Garage Science
« Reply #4 on: 11/03/2009 13:43:47 »
I've got a 'spare' acoustic guitar you can test it on...
 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8134
  • Thanked: 53 times
    • View Profile
Cello vibrations and how a violin bow works - Garage Science
« Reply #5 on: 11/03/2009 13:44:37 »
It may be possible to use interferometry to record the minute movements of the cello's surface e.g. reflecting a laser off it, (use a diverging lens to create a cello sized disc of monochromatic light), and record the changing interference patterns on camera...

http://www.wim.ma.htwg-konstanz.de/de/inhalt/50_Studierende/20_Studien-,%20Bachelor%20und%20Projektarbeiten/Poster_Speckle_Interferometrie_Grundler_2.pdf

http://www.h.amu.cz/zvuk/studio/dokumenty/Lit145.pdf

http://en.wikipedia.org/wiki/Laser_Doppler_Vibrometer

(No sand, talc or flour required)
« Last Edit: 11/03/2009 13:54:41 by RD »
 

Offline daveshorts

  • Neilep Level Member
  • ******
  • Posts: 2583
  • Physics, Experiments
    • View Profile
    • http://www.chaosscience.org.uk
Cello vibrations and how a violin bow works - Garage Science
« Reply #6 on: 11/03/2009 16:26:03 »
Yes a guy I know who does some science lectures called Mark Lewney did a PhD on this subject. However It would require quite a powerful laser to make it work - or I guess a strobed much less powerful laser and a long exposure time.
 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8134
  • Thanked: 53 times
    • View Profile
Cello vibrations and how a violin bow works - Garage Science
« Reply #7 on: 12/03/2009 00:58:35 »
No indication of the power of the laser used on this guitar, (image published 1983)...



http://books.google.co.uk/books?id=iiCZwwFG0x0C&pg=PA225
« Last Edit: 12/03/2009 01:01:33 by RD »
 

Offline daveshorts

  • Neilep Level Member
  • ******
  • Posts: 2583
  • Physics, Experiments
    • View Profile
    • http://www.chaosscience.org.uk
Cello vibrations and how a violin bow works - Garage Science
« Reply #8 on: 30/07/2009 09:56:31 »
From Mark Lewney

"
Since you ask about their origin, they were made in the Cardiff Uni
acoustics lab using a powerful green YAG laser (can't remember the exact
power - think it averaged a few kW). In fact, I once blew the power amp
on it: holograms need silence, since if the whole object shakes more than
a quarter wavelength you see diddly squat. The fan on this thing was
making quite a racket, so I muffled it with my coat during exposure, then
remembered to remove it afterwards.

Until the time I forgot. Those big capacitors make a hell of a mess when
they get so hot they explode."
 

The Naked Scientists Forum

Cello vibrations and how a violin bow works - Garage Science
« Reply #8 on: 30/07/2009 09:56:31 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums