two
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Joined: Thu Dec 19, 2013 4:43 pm
Occupation: homeschool mom

### hypothesis for sympathetic vibration experiment

Hi, how do I develop a hypothesis for the sympathetic vibrations experiment on guitar strings?

tdaly
Former Expert
Posts: 1415
Joined: Sat Nov 08, 2003 11:27 pm
Occupation: Planetary Scientist

### Re: hypothesis for sympathetic vibration experiment

Hi two,

Good question. This Science Buddies article has some great information about how to write a hypothesis: http://www.sciencebuddies.org/science-f ... esis.shtml

For this particular project, think about what you expect will happen when different strings of the guitar are plucked. Do you think that all of the strings will sympathetically vibrate? Or only some of the strings? Do you think that one string in particular will cause the most sympathetic vibrations? A hypothesis for this project could include your guesses about the answers to these questions. Remember that a hypothesis is an educated guess. It doesn't have to be correct.
All the best,
Terik

two
Posts: 2
Joined: Thu Dec 19, 2013 4:43 pm
Occupation: homeschool mom

### Re: hypothesis for sympathetic vibration experiment

Thanks. But how does she get the education to form an educated guess. Right now she has no idea, no guesses.

tdaly
Former Expert
Posts: 1415
Joined: Sat Nov 08, 2003 11:27 pm
Occupation: Planetary Scientist

### Re: hypothesis for sympathetic vibration experiment

Hi two,

Ah, now I see your question more clearly. Thanks for clarifying!

A good place to start is with sound waves, since the sympathetically vibrating strings are responding to sound waves generated by the plucked string. This website provides a nice discussion of sound waves, written for at an upper middle school level:

http://www.school-for-champions.com/sci ... rYsAvRDuSo

This website has several activities that explore sound and sound waves: http://www.discoveryeducation.com/teach ... -waves.cfm

Every string vibrates at a fundamental frequency, which is determined by factors like the string's length and thickness. When you pluck a guitar string without any fingers on the fret, the pitch (or frequency) of the sound wave you hear is the natural frequency of the string. Whether or not plucking one string causes another string to vibrate sympathetically depends on whether the two strings share any overtones , which are multiples of the strings' fundamental frequencies. These following two Wikipedia articles discuss resonances. The second article specifically addresses resonances in string instruments.

http://en.wikipedia.org/wiki/Acoustic_resonance (up to the end of the section called "string resonance in musical instruments")
http://en.wikipedia.org/wiki/String_resonance

The equations in the first article can be used to calculate the fundamental frequency and overtones of a string. Since this is a middle school project (or, it's posted in the middle school forum), you can probably leave out the detailed math, unless math is a strong point of your student.

If you have questions about anything in these articles, post back and I'll try to clear things up for you.