Activity: Operating the Equipment

￿Measuring the Sound Frequency

uPosition the two wood blocks so there is about 40cm between them, and then lightly pluck the center of the string to produce a sound.

uRecord the sound with the Audio Measurement Setup, perform FFT analysis, and view the frequency distribution.

1Monochord

2Desk

3Distance Between Blocks: 40cm

4Finger

uPosition the two wood blocks so there is about 20cm between them, and then lightly pluck the center of the string to produce a sound.

uRecord the sound on the Audio Measurement Setup, perform FFT analysis, and view the frequency distribution.

1Monochord

2Desk

3Distance Between Blocks: 20cm

4Finger

uCalculate values for f12/f11, f22/f21, f21/f11, and compare them.

uNext, note the relationship with each of the above values with the value 2.

uTry 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.

2-6-2

English

Measurementasurement

￿Calculator Operation

uPrepare the Audio Measurement Setup for recording.

uFind the applicable program in the Program Library (P.2-16-2), input it into your calculator, and then run it.

uPerform FFT analysis on the sound recorded when the blocks are 40cm apart, and study the frequency distribution.

1 Waveform

 

S

: Sound Volume

 

2 Frequency

 

t(s)

: Time

Distribution

 

N(counts) : Number of

3 f11

 

 

Counts

4 f12

 

f (Hz)

: Frequency

 

 

 

 

uPerform FFT analysis on the sound recorded when the blocks are 20cm apart, and study the frequency distribution.

1 Waveform

 

S

: Sound Volume

 

2 Frequency

 

t(s)

: Time

Distribution

 

N(counts) : Number of

3 f21

 

 

Counts

4 f22

 

f (Hz)

: Frequency

 

 

 

 

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uConsider the reason why f12/f11, f22/f21, and f21/f11 are values in the vicinity of 2.

uConsider the reason why f12/f11, f22/f21, and f21/f11 are not exactly 2.

uFind out how the natural frequency changes when you use a different type of string.

uModify 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.

1Pulley

2Weight

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