Science Fair Experiment

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  • Topic: Guitar, Violin, Fingerboard
  • Pages : 13 (1906 words )
  • Download(s) : 80
  • Published : December 27, 2010
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Rock it out loud:
discovering the location of harmonies that make your guitar sing.

Purpose:
To identify the locations of harmonics on an acoustic guitar and relate them to guitar string lengths.

Hypothesis:
If I pluck the sixth string of the guitar from frets nine- twelve, then those frets will not produce harmonics that are able to be heard clearly.

Materials:
Acoustic guitar ( adult or child sized)
Cloth tape measure, metric
Lab Notebook

Procedures on finding harmonics on your guitar:
1.Select a string and starting at the twelfth fret, try to play a harmonic in that fret by lightly damping the string above the twelfth fret. a.If a harmonic is heard (and you hear a ringing, bell-like tone), then mark that location in your data table with a filled-in black circle. b.If a harmonic is not heard (if the string sounds dead or dull or makes no sound at all when plucked), then mark that location in your data table with an open circle. 2.Continuing on with the same string, repeat step 1 for all frets, from fret 11 down to fret 1. 3.Repeat steps 1–2 for two additional strings.

Procedures on relating the location of the harmonics to the location of the strings: 1.Measure the length of one string, from the nut to the bridge, with the tape measure. (All strings are the same length on a guitar, so it does not matter which one you choose.) You will probably need a helper to take this measurement accurately. Write down your measurement in your lab notebook. 2.Make a data table for each string tested, like the one below. The first entry in the data table is an example, so the numbers in your data table may look different. Continue reading the rest of the steps to understand the information you'll record and calculate. You will be calculating at what fraction of the string's length each of the harmonics were heard. 3.Using the data table that looks like your fretboard, list all of the fret numbers where a harmonic was heard (all the filled-in circles) in the first column of the first string's data table. 4.Measure the distance from the nut to the fret where each harmonic was heard with the tape measure and record this value in the second column of your data table. 5.Calculate the fraction of the total string length by dividing the distance from the nut to the fret by the string length, and enter your calculation in the third column of the data table. 6.Obtain the reciprocal of the fraction and enter that in the fourth column of the data table. 7.Figure out the closest whole number to the reciprocal to obtain the harmonic number for the fifth column. 8.Repeat steps 3–7 for the other two strings that you tested.

String One Data Table
Fret Number where a harmonic was heard
Distance from a nut to a fret where a harmonic was heard
Fraction of the total string length ( Distance from the nut to the fret, divided by the string's length) Reciprocal of the fraction
Closest Whole integer (harmonic number)
12 y/n

/66=

11 y/n

/ 66=

10 y/n

/66=

9 y/n

/66=

8 y/n

/66=

7 y/n

/ 66=

6 y/n

/66=

5 y/n

/66=

4 y/n

/ 66=

3 y/n

/66=

2 y/n

/66=

1 y/n

/66=

String Two Data Table
Fret Number where a harmonic was heard
Distance from a nut to a fret where a harmonic was heard
Fraction of the total string length ( Distance from the nut to the fret, divided by the string's length) Reciprocal of the fraction
Closest Whole integer (harmonic number)
12 y/n

/66=

11 y/n

/ 66=

10 y/n

/66=

9 y/n

/66=

8 y/n

/66=

7 y/n

/ 66=

6 y/n

/66=

5 y/n

/66=

4 y/n

/ 66=

3 y/n

/66=

2 y/n

/66=

1 y/n

/66=

String Three Data Table
Fret Number where a harmonic was heard
Distance from a nut to a fret where a harmonic was heard
Fraction of the total string length (...
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