Exploratory Musical Instruments



WORKSHEET- CHARACTERISTICS OF SOUND

Section A: Musical Instruments Exploratory

(1) Percussion instruments/ Handmade drum.

(i) When you hit the percussion instruments with different strengths, how was the sound different?

Harder we hit, the louder the sound.

(ii) What do observe when you drop a few grains of rice on top of the membrane of the hand drum and hit it with different strengths?

The grains bounce atop the membrane when we tap lightly. It jumps off when we hit really hard.

(iii) Can you suggest a reason for the above observation (ii)?

The vibration of the membrane is transferred to the grains. The more energy transfer, the more the grains are disturbed.

(2) Phonofiddle imitation

(i) Set up the given materials according to the picture above.

How did changing the length of the vibrating part of the rubber band

change the sound?

The longer the rubber band, the lower the sound (pitch). Vice versa.

(ii) Name a musical instrument you know that exhibit the same behaviour in sound variation.

Guitar, violin or any string instrument.

(iii) Lift the cup off the ruler and pluck the rubber band by itself.

What do you think is the use of the cup?

When lifted, the sound produced by plucking the rubber band becomes

louder. The cup is used to amplify the vibration of the rubber band.

(3) Handmade plastic guitar

(i) Shift the chopstick along different positions and compare the sounds produced by plucking/ strumming each string. How is the sound produced different?

The pitch of the guitar changes as the chopstick moves along different positions.

(ii) Pluck the strings of the plastic guitar. Recall the sound produced by the actual musical instrument – guitar. How are the tones of the sound different comparing both guitars?

The sound from an actual guitar instrument is more distinct. The tone from the plastic guitar is less clear.

Section B: Characteristics of Sound

(1) Fill in the blanks.

(2) Draw a waveform on (b) that represents a softer sound than waveform (a).

(3) State the unit of sound level.

Decibel (dB).

(4) List the Threshold of Hearing and the maximum sound level that a human ear can take.

0 dB and 160 dB.

(5) Fill in the blanks.

The ____________ of the vibration affects the ________ of sound. The ____________ the frequency, the higher the pitch of the sound.

(6) Your friend wants to increase the pitch of the Phonofiddle. Describe one way he can do that.

1. Tighten the string. 2. Shorten the length of the string.

3. Use a thinner string of smaller mass per unit length.

(7) What determines the quality of sound?

The waveform.

(8) Fill in the missing portions of the concept map.

Reflection

(9) Describe why you personally think sound is interesting and list one thing you have learnt from today’s lesson.

Section C: Check your Understanding

(1) The "buzz" of a mosquito produces an intensity having a 40-dB rating. How many times more intense is the sound of normal conversation if it has an intensity rating of 60-dB?

a. 2

b. 20

c. 100

d. 200

e. 400

(2) Human sounds are produced by the vibrations of the vocal cords. Like the pitch of a vibrating string, the pitch of a human sound depends on

a. the tension, friction and length of the cords.

b. the friction, length and thickness of the cords

c. the cross-sectional area, length and elasticity of the cords.

d. the tension, length and thickness of the cords

(3) A microphone is connected to the y-input of a cathode ray oscilloscope. Three different sounds are made in turn in front of the microphone. Their traces A, B, C produced on the screen, are shown below. The controls of the oscilloscope remain unchanged throughout the experiment.

a. Which trace is due to the loudest sound? Explain your answer.

b. Which trace is due to the sound with the lowest pitch? Explain your answer.

a. Trace B has the loudest sound as the CRO traces the wave with the largest amplitude compared to the other 2 traces.

b. Trace A has the lowest pitch as its frequency is the smallest. Traces B & C have the same frequency and thus they have a comparatively higher pitch than Trace A.

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The setup imitates an old fashioned instrument called a Phonofiddle.

Answer:

(d)

Answer:

40dB => 104

60dB => 106

(c) 100 times more intense.

Louder sound

__________ amplitude of vibration.

__________ you hit the membrane.

That is, more __________ transfer.

depends on waveform.

(b)

(a)

depends on frequency.

depends on the amplitude of vibration.

Quality or Timbre

Soft

Clearer

Characteristics of sound

Mixed

High

Low

pitch

frequency

Larger

Pitch

Loudness

higher

Loud

energy

Harder

Pluck here.

Try listening by putting your ear at the cup.

Place your finger along the ruler

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