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Activity: Operating the EquipmentActivity: Operating the Equipment
MeasurementMeasurement
2-6-2
í Measuring the Sound Frequency
u Position the two wood blocks so there is about 40cm between them, and then lightly pluck
the center of the string to produce a sound.
u Record the sound with the Audio Measurement Setup, perform FFT analysis, and view
the frequency distribution.
u Position the two wood blocks so there is about 20cm between them, and then lightly pluck
the center of the string to produce a sound.
u Record the sound on the Audio Measurement Setup, perform FFT analysis, and view the
frequency distribution.
u Calculate values for f
12
/f
11
, f
22
/f
21
, f
21
/f
11
, and compare them.
u Next, note the relationship with each of the above values with the value 2.
u Try changing the distance between the blocks, the location where you pluck the string,
and the strength of the pluck, and see how it affects the frequency.
í Calculator Operation
u Prepare the Audio Measurement Setup for recording.
u Find the applicable program in the Program Library (P.2-16-2), input it into your calculator,
and then run it.
u Perform FFT analysis on the sound recorded when the blocks are 40cm apart, and study
the frequency distribution.
u Perform FFT analysis on the sound recorded when the blocks are 20cm apart, and study
the frequency distribution.
1 Monochord
2 Desk
3 Distance Between
Blocks: 40cm
4 Finger
1 Monochord
2 Desk
3 Distance Between
Blocks: 20cm
4 Finger
1 Waveform
2 Frequency
Distribution
3 f
11
4 f12
1 Waveform
2 Frequency
Distribution
3 f
21
4 f22
S :Sound Volume
t(s) :Time
N(counts):Number of
Counts
f(Hz) :Frequency
S :Sound Volume
t(s) :Time
N(counts):Number of
Counts
f(Hz) :Frequency
55555555555555555555555
5555555555555555555555
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Other Things To Do
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u Consider the reason why f12/f11, f22/f21, and f21/f11 are values in the vicinity of 2.
u Consider the reason why f
12/f11, f22/f21, and f21/f11 are not exactly 2.
u Find out how the natural frequency changes when you use a different type of
string.
u Modify the monochord as shown in the illustration below, and adjust the weight so
it changes the tension of the string. Study how the natural frequency is affected by
changes in the tension of the string.
1 Pulley
2 Weight