PRACTICAL 3

TOPIC: SOUND QUALITY

AIM/ OBJECTIVE: To demonstrate and explain how different sound quality is

produced.

THEORETICAL KNOWLEDGE:

Sound is a vibration that is transmitted through a solid, liquid, or gas. Sound

composes of frequencies within the range of hearing and a level of sufficiently strong

to be heard or the sensation stimulated in organs of hearing by such vibrations.

There is an original source of the wave. Some vibrating object is capable of

disturbing the first particle of the medium. The sound wave is transported from one

location to another by means of particle-particle interaction.

Sound waves are longitudinal waves which require a medium for its

propagation. Sound is produced by vibration. It pushes and pulls in the air adjacent

to it, causes rapid change in the air pressure.

Loudness is really a measure of the intensity of sound. The loudness of a

sound is considered to be high or otherwise depends on the hearing ability of the

person. Amplitudes determine loudness. It is measured in decibel. The bigger is the

amplitude, the louder is the sound.

The pitch of a sound or a musical note is an indication of how high or low the

sound is. The pitch of sound is determined by its frequency. A high pitch

corresponds to a high frequency.

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STATEMENT OF PROBLEM:

How different sound quality is produced?

HYPOTHESIS:

Different sound quality is produced by the different pitch due to its frequency.

If the air column is higher, the pitch produced by blowing across top of bottle

is lower.

In the mean while, if the water in the bottle is higher or more, the pitch

produced by tapping on side of the bottle is lower.

INSTRUMENTS AND MATERIALS:

Instruments Materials

3 identical glass bottles Water

Tuning fork

Bowl

Meter rule

Pencil

VARIABLES:

Manipulated: Length of column of air and height of water

Responds: Pitch produced by blowing and tapping

Kept constant: Materials being measured

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PROCEDURE:

Activity: Demonstrating The Production Of Different Sound Quality

1. A bowl is filled with water. A tuning fork is tap against the sole of shoes.

The tip of one of the prongs is placed in the water. The observation is

recorded.

Picture 1: Placing the prong in the water

2. The tuning fork is tap again. What will happen when it is hold near the ear

is predicted. What is heard is recorded.

3. The water is put into 3 identical glass bottles so that bottle A is ¼ full,

bottle B is ½ full, and bottle C is ¾ full.

Bottle A Bottle B Bottle C

Picture 2

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4. The distance from the top of each bottle to the surface of the water is

measured. Then, the height of the water in each bottle is measured. The

measurements are recorded.

Picture 3: Measuring the length of air column and the height of water.

5. The difference in pitch will heard if blow across the top of each bottle in

turn is predicted. The reason of predictions is given.

6. The prediction is tested by blowing over the top of each bottle. The sound

produced is listened. Each sound is described in terms of its pitch- low,

medium or high. The pitch of each sound is recorded.

7. When the side of a bottle is gently tapped with a pencil, another sound is

produced. The sound produced is compared with the sound produced by

blowing across the top of the bottle.

Picture 4: Blowing the top of each bottle Picture 5: Tapping the side of bottle

8. The prediction is tested by tapping on the side of each bottle with a pencil.

The pitch of each sound is recorded.

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RESULTS:

Bottle Length of

column of air

(cm)

Height of

water (cm)

Pitch produced by

blowing across top

of bottle

Pitch produced

by tapping pencil

on side of bottle

A 9.0 cm 3.0 cm Low High

B 6.0 cm 6.0 cm Medium Medium

C 3.0 cm 9.0 cm High Low

Table 1

DISCUSSION:

1. When the tuning fork is tap against the sole of shoes and the tip of one of the

prongs is placed in the water, the water is splashing. This is because the

vibrating tuning fork causes the water to vibrate.

2. When the tuning fork is tap again and hold near the ear, a sound of vibration

note is heard because the vibrated tuning fork causes the air around the

prong vibrate too producing sound. The sound is said to be transferred

through the solid (prong of the tuning fork).

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3. When I blow across the top of each bottle, it makes the air inside the bottle

vibrate. Small air spaces vibrate more rapidly than large air spaces causes

the frequency of sound to be higher in the low length of air column compared

to the high air column. So, a little air in the bottle or a low length of column of

air causes a high pitch- note to be produced when blowing across the top of

bottle.

Here, if the air column is higher, the pitch note produced is a lower due to the

lower sound frequency. In sum, if the air column increases, the pitch- note will

decrease. The sound is said to be transmitted through the gas (air).

4. When the side of a bottle is gently tapped with a pencil, another sound is

produced. After compared with the sound produced by blowing across the top

of the bottle, I found that the pitch of the sound- note depends on the amount

of water in the bottle, not depends on the air column anymore. Tapping the

side of the bottle causes the bottle to vibrate and the vibration is transferred to

the water in. The water vibration produces sound.

Here, the more is the water, the lower is the pitch because the vibration

produced in the water is slower due to the large amount of water that needs

more energy to vibrate the molecule of water in. It causes the sound

frequency to be lower too. That is why the pitch produced is lower. In sum, if

the amount of water increases, the pitch- note will decrease. The sound is

said to be transmitted through the water.

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PRECAUTIONS:

1. We must be careful of the environment during the experiment. The fan should

be switched off because it can interrupt the vibration of the air or water in the

bottle.

2. Be careful while tapping the bottle using the pencil because the bottle is a

kind of glass that is possible to break.

3. We must listen at the sound- note produced at least three times to get a more

accurate pitch to be matched with the length of air column and the height of

the water in the bottle.

QUESTIONS AND ANSWERS:

1) In procedure 6, which bottle produced the highest pitch? What caused

the change in pitch from bottle to bottle?

The bottle that produced the highest pitch is Bottle C.

The change in pitch from bottle to bottle is because of the difference of length

of air column in each bottle. When we blow across the top of each bottle, it

makes the air inside the bottle vibrate. The small air space vibrates more

rapidly than the large air spaces causes the sound frequency to be high. So,

the lowest air column in the bottle produces the highest pitch, while the

highest length of air column produces the lowest pitch.

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2) Describe how the sound is produced in procedure 8? Which bottle

produced the highest pitch? What caused the change in pitch from

bottle to bottle?

In procedure 8, the sound is produced by tapping the pencil on the side of

each bottle. This makes the bottle vibrate. The vibration of the bottle causes

the water in the bottle to vibrate. So, sound is produced.

Bottle A produced the highest pitch.

The pitch- note of the sound depends on the amount of water in the bottle.

The pitch note becomes lower because the amount of water increases. The

molecule of more water needs more energy to vibrate, making the pitch note

becomes lower because of the lower frequency of sound produced in.

3) Compare the sounds you produce by blowing across the top of the

bottles with those produced by tapping on the bottles. What was the

difference in pitch for each bottle? Explain your observation.

Bottle A (¼ full of water) produces a low pitch when blowing but high pitch

when tapping, bottle B (½ full of water) produces same pitch of medium in

both situation, while bottle C (¾ full of water) produces a high pitch when I

blow but low pitch when I tap its side.

The difference of pitch produced in bottle A because the high length of air

column that gives a low amount of water in the bottle makes the pitch

produced low when blowing and high when tapping. The high length of air

column needs more energy to vibrate, so the frequency of sound produced is

lower makes the pitch to become lower. In the meanwhile, the low height of

water in causes the molecule of water to vibrate rapidly, produces high

frequency then high pitch of sound note. What happen in bottle C is opposite

to this situation because bottle C has low length of air column and high height

of water.

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In sum, the pitch of sound depends on the length of air column when blowing

and depends on the amount of water in the bottle when tapping its side.

4) By looking at your data table, how does the length of air column of air

affect the pitch? How does the height of the water affect the pitch?

If the length of air column of air increases, the pitch produced will decrease

while if the height of the water increases, the pitch produced will decrease.

5) What conclusions can you draw about the relationship between the

sound produced and the medium through which the sound travels?

Sound needs medium of gas, liquid or solid to propagate or travel, where

different medium of sound propagation will produce different speed of sound.

The speed of sound in air is 346 ms-1, water 1500 ms-1 and granite is 5400

ms-1. So, the sound travels through faster in solid material. It is because, the

molecules are packed together tighter in solid so the vibration can be easily

produced and moved from one molecule to another.

In conclusion, the sound travels fastest in solid medium, travels in medium

speed in water n slowest in the gas. This is because the distance between

molecules in the solid material is the tightest.

6) Think: violins are stringed instruments. Flutes and clarinets are

Woodwinds and trumpets are brass instruments. What do all these

musical instruments have in common?

All these musical instruments have a device that can vibrate, creating sound

waves in common. The instruments have a string and a thin piece of wood or

metal commonly.

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Mastery of knowledge and skills questions:

a) What have you learnt from the practical?

This experiment gives me a better understanding about sound concept

practically through experiment after discussed in lectures. I can learn how

different sound quality is produced through the different pitch produced by

different sound frequency. Here, the pitch concept of sound is proven in front

of me. It makes me understand enough about the pitch. I can determine the

relationship of length of column of air and the height of water in a bottle with

the pitch produced.

Besides, this experiment has taught me how to make a correct observation

and how to explain the reasons scientifically towards the observing about the

sound. I also learn how to handle the instruments and materials involved in

this experiment correctly. The most important is I get to know the reasons of

the differences in pitch produced when blowing and tapping the bottle.

b) Which part of the primary science curriculum teaches this particular

topic?

Year 5, topic “Energy of Sound”.

c) Discuss how you can use the above practical in your teaching and

learning?

I will design a simpler experiment than this one so that it is suitable with Year

5 students to understand the content of “Energy of Sound” topic. I will give a

clear briefing to the students regarding the concept of sound first before doing

the experiment to make sure they understand the concept for a smooth

experiment.

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Besides, a strategy of demonstration can also be done to explain this concept

of sound. I will demonstrate to the students first on how to use the apparatus

well in order to get the accurate result of how the pitch is produced. Then,

they will do it themselves to get the result as proven in such like an

experiment, following my demonstration before.

Besides that, I can also use a simulation strategy by relating the concept of

sound with the outside situation that happens in students’ daily life which

applies the concept. Here, the musical instruments can be the example for

the situation that applies the concept of pitch. So, the students will get a

clearer picture to understand the concept as it is related to their live.

d) What was the role of the teacher in the above practical?

The above experiment needs teacher to act as a facilitator, guider and

demonstrator. Teacher guides students how to do the experiment and being

together with the students along the experiment in order to facilitate them.

Indeed, teacher always demonstrate how to use the apparatus first before let

the students do themselves. A correct and careful use of apparatus is very

important in this experiment as it involves such an easy broken apparatus like

glasses. So, a well- conducted scientific skill is really essential for the

students’ safety indeed.

Besides, teacher should encourage the students in their application of

scientific skills such as solving problem, measuring and analyzing. Here, the

support from the teacher is important for the students to elaborate their

answers on the way to understand how sound is produced and yes, they will

learn the best from the hands on activity in this experiment to prove the

concept of sound.

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CONCLUSION:

Hypothesis is accepted. Different sound quality is produced by the different

pitch due to its frequency.

The pitch produced when blowing across the top of each bottle depends on

length of air column in the bottle, where if the air column is higher, the sound

frequency produced in the vibrated air is lower, thus the pitch produced by

blowing is lower.

In the mean while, the pitch produced when tapping the side of the bottle

depends on the height or amount of water in the bottle, where if the water in

the bottle is higher or more, the sound frequency produced in the vibrated

water is lower, then the pitch produced by tapping is lower.

REFERENCES:

Foo Seng Teek, Yee Cheng Teik, Chong Geok Chuan, Lee Beng Hin. (2009). Success Physics SPM. The Pitch of Sound. Selangor. Oxford Fajar Sdn. Bhd.

http://galileo.phys.virginia.edu/outreach/8thGradeSOL/SoundStationsFrm.htm. (2009). Sound Station. Accessed in 20 March 2010.

http://exhibits.pacsci.org/music/MusicPhysics.html. (2008). Sound of Musical Instruments. Accessed in 21 March 2010.

http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/sound/u11l1a.html. (2008). Sound Lesson. Accessed in 21 March 2010.

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