Handbook p3 sound

Agastya International Foundation

Sound Handbook P3

“We cannot teach people anything; we can only help them discover it within themselves.�

-Galileo Galilei (1564-1642)

1

Handbook P3 Sound OVERVIEW OF HANDBOOK ABL

CONCEPT

NO OF ACTIVITIES

TIME min PAGE NO

ABL1

What is sound?

2

40

ABL2

How does sound travel?

3

60

ABL 3

Properties of sound

8

60

ABL 4

Reflection of sound and Echo

3

70

ABL 5

How do we hear sounds?

1

30

ABL 6

Musical Instruments

3

60

Total time

320 minutes

ABLs WITH REFERENCE TO STANDARD S.No. 1 2 3 4 5

STANDARD 8 and 9 8 and 9 9 9 8 and 9

PREFERRED ABL ABL 1 ABL 2 ABL 3 ABL 4 ABL 5

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2

LIST OF FIGURES, CHARTS AND WORKSHEETS S. No

Name

Page No

Fig 1

Vibrating Ruler

7

Fig 2

Feeling the voice box

7

Fig 3

Toy Phone

13

Fig 4

Sound can travel through solids

13

Fig 5

Sound travels through liquids

15

Fig 6

Transverse and Longitudinal waves using a slinky

18

Fig 7

Compressions and rarefactions

19

Fig 8

Cut Straw

23

Fig 9

Sound of varying frequency or pitch

25

Fig 10

Reflection of sound model

34

Fig 11

Doppler Effect

38

Fig 12

Anatomy of human ear

44

Fig 13

Outer ear

44

Fig 14

Middle ear

44

Fig 15

Inner ear

45

Fig 16

Shoebox guitar

53

Chart 1

Sounds of differing pitch but same amplitude

29

Chart 2

Soft and loud sounds of same frequency

29

Chart 3

Stringed instruments

53

Chart 4

Wind instruments

55

Chart 5

Percussion instruments

57

Chart 6

Simple xylophone

57

Note to Instructor: All the figures in this handbook are for the Instructor’s reference only. The Charts need to be printed and shown to the learners during the course of the activity. Worksheets need to be printed out in advance for the learners. The number of worksheets required is mentioned in the Material List.

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3

ABL 1What is sound?

Activity

Learning objective

1.1

Sensing the world through sounds

Key messages

  

1.2

What is sound and how is it produced?

 

Sources of sound exist all around us One of the useful senses that humans possesis hearing Your ears help you to hear sounds Sound is a form of energy Sound is produced by vibrating bodies

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Time (min)

15

25

Time: 15 min

4

ABL 1.1 LEARNING OBJECTIVE – Sensing the world through sounds Note to Instructor–This activity is used as an introduction to sound. Students are blindfolded and asked to listen to various sounds around them and identify them.

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Strips of cloth or handkerchief to be used as blindfolds White paper sheets and pencil/pen

1 per every other

2

student 1 per student

Things to do: Not Applicable

Safety Precautions: Make sure the students sit in one place and don’t move around when they are blindfolded, to avoid getting hurt. A student can be assigned as a guide to another student who is blindfolded to make sure that she/he is safe at all times.

Make sure the children walk very slowly and turn gently .

SESSION Link to known information/previous activity Not Applicable Procedure Take the students outdoor if possible; else perform this activity in the classroom. Blindfold the students and ask them to listen to the various sounds around them. Ask them to make a note of the sounds they hear and let them try to identify them. Remove the blindfolds and let them make a note of the various sounds that they heard and compare it with the notes of their classmates.

UNDERSTANDING THE ACTIVITY Leading questions 1. What are the various sounds that you heard?

2. Can you identify them?

3. Did your classmates hear similar sounds?

Discussion and Explanation Discussion Item 1: Sounds around us  Every day we hear sounds from various sources like people, chatter of students in a classroom, animals, birds, vehicles, phones, machines, etc.

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5     

Sound is one of the most important ways to sense our surroundings and communicate with other people One of the important and useful senses that human posses is the ability to hear the sounds produced around us.

Our ears help us to hear sounds around us.

We are able to communicate to others with the help of sound.

People that are unable to hear sounds depend upon other senses such as sight touch and smell, to make sense of the world around them.

KEY MESSAGES   

Sources of sound exist all around us One of the useful senses that humans posses is hearing Your ears help you to hear sounds

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

Time: 25 min

ABL 1.2 LEARNING OBJECTIVE – What is sound and how is it produced?

Note to Instructor - These activities show how every sound you hear is produced because of vibrations.

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Common Plastic Scale

1 per class

2

Table

1 per class

3

Balloon

1 per class

Things to do N.A Safety Precautions N.A

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SESSION Link to known information/previous activity In the previous activity we learned that we hear various sounds around us. Now let’s see how sound is produced.

Procedure Complete 1.2a, 1.2b and 1.2c given below before starting discussion.

1.2a Demonstration1

Hold a ruler on a table as shown in the diagram and vibrate the protruding edge.

Ask the children to observe movement of the ruler carefully.

Precaution – Be careful with the sharp edge of the ruler

Figure 1: Vibrating Ruler

1.2bin pairs

Divide learners into pairs.

Ask each learner to place 4 fingers across the front of his/her throat and observe what happens when s/he speaks.

Ask learner to repeat the same by placing 4 fingers across the partner’s throat.

Precaution- Be careful that learners do not press too hard on partner's throat.

Figure 2: Feeling the voice box

1.2c Demonstration Inflate the balloon fully and close it with your thumb and index finger.

Now, slowly, let the air escape and twist and stretch mouth of the balloon to produce different sounds.

UNDERSTANDING THE ACTIVITY Leading questions 1. What is common between the three activities?

2. What did you feel when you touched yourthroat or your friend’s throat?

3. Did you feel anything different when you or your friend was quiet?

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7 Discussion and explanation Discussion Item 1: The following points are about how sound is produced when there are vibrations  We have seen that the ruler moves rapidly to and fro. These to and fro movements are called vibrations.  Similarly, when we speak, the vocal cords in the voice box [larynx] vibrate.  As air escapes from the balloon through the narrow opening, the elastic balloon material vibrates.  In each of the above activities we heard a sound ONLY when there was a vibration.  When the ruler, your vocal cords and the balloon membrane vibrate, they cause the air molecules surrounding them to vibrate.  It is this vibration of air molecules that reaches our ear as sound.  We can see that squeezing and stretching the balloon in different ways produce different sounds.

This is similar to how we're able to make different sounds through our voice box.  We should know that vibrations cause all sounds. But all vibrations do not cause sound. We will see why later.

Discussion Item 2: The following points are about how sound is a form of energy  When the scale vibrates the energy from the movement of the scale is transferred to the surrounding air.  As the scale vibrates, the energy transferred makes the air molecules of the medium to vibrate. Due to elasticity the vibrations reach our ear.  This energy (in the vibrations) is called sound energy.  Typically, energy in sound is far less than other forms of energy you are familiar with.

KEY MESSAGES  

Sound is a form of energy Sound is produced by vibrating bodies

LEARNING CHECK Distribute learning check worksheet that includes the questions below to assess students on ABL1. Key is provided here for your reference.

1. Whenever a sound is made, something vibrates. a. True (Answer) b. False 2. Which of the following statement is NOT true? a. In the flute the sound is produced due to a vibrating air column b. Vibrations cause all sounds. But all vibrations do not cause sound c. Sound is not a form of energy because there is no evidence to prove it (Answer) d. None of the above 3. In human beings, the vibration of the ____________produces sound. a. Eardrums b. Vocal cords (Answer) c. Nasal cavity d. None of the above Agastya International Foundation. For Internal Circulation only.

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8 4. In which of the following is sound produced? a. Making a column of air vibrate b. Plucking a string c. Flapping of wings by birds d. All of the above (Answer) 5. What role does energy play in sound? a. Sound waves have nothing to do with energy b. Sound waves carry energy (Answer) c. Energy is present in loud sounds only d. Energy is present is very low sounds only

TRY IT YOURSELF 1. Look at different things in your home or school that produce sound. For example check musical instruments like Veena, Sitar, Mrudungam, Drum, Dholak, Shenai, and Naadaswaram. Find out what part of the instrument vibrates to create sound.

2. You have all seen loudspeakers in temples and other functions. If you can go near it and place your hand gently on the membrane, you will feel the vibrations. Be careful not to go near it if the sound is very loud, or it will affect your ear.

INTERESTING INFORMATION 1. Most sounds you hear from the sound of the wind to the roar of a jet are actually moving air.

2. Sound is used by many animals to detect danger and be warned of possible attacks before they happen.

WEB RESOURCES http://library.thinkquest.org/19537/

REFERENCES http://resources.woodlands-junior.kent.sch.uk/revision/science/sounds.html http://www.bbc.co.uk/bitesize/ks2/science/physical_processes/sound/quiz/q75676573/

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9

ABL 2 How does sound travel?

Activity

Learning objective

Key messages

Time (min)

2.1 2.2 2.3

Can sound travel through solids?

Can sound travelthrough liquids?

Does sound require a medium to travel?



Sound travels through solids

15



Sound travels through liquids

15



Sound waves can travel through all the three forms of matter solids, liquids and gases Sound always requires a medium to propagate Sound is a form of energy Sound travels as mechanical waves In sound propagation, it is the energy of the sound that travels and not the particles of the medium

20

 2.4

How does sound travel?

  

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10

10

ABL 2.1

Time: 15 min

LEARNING OBJECTIVE –Can sound travels through solids?

Note to Instructor – A set of three small activities to show that sound travels through solids, liquids and gases.

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Electric Torch

1 per class

2

Wooden or metal Table

1 per class

Things to do: Not Applicable Safety Precautions: Not Applicable

SESSION Link to known information/previous activity In the previous activity we learned that sound is produced due to vibrations. In this activity let us see what is required for sound to travel.

Procedure Flash the torch light against a wall or closed door. Let the children observe what happens.Now, have two of the students stand on either side of the door or wall. Let one of the students make some kind of loud sound by banging against the door/wall or shouting from the other side of the wall or door.

UNDERSTANDING THE ACTIVITY Leading questions 1. What did you notice when the torchlight was flashed on the wall/door?

2. What happened when the student standing on the other side of the door/wall made a sound?

Discussion and Explanation Discussion Item 1: The following points are about how sound travels through solids.  We have learned in lower classes that light does not travel through wood/concrete and hence casts a shadow  But however, we were able to listen to the sound made on the other side of the wall/door.  This is because sound is able to travel through the wall/door.  If some of you have made toy phones in the past. The child speaking into a cup makes the bottom of the cup to vibrate.Since the string is tightly attached to the bottom of the cup, the vibrations of the cup are transmitted to the string. These vibrations travel down the string, and cause the Agastya International Foundation. For Internal Circulation only.

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11 bottom of the receiver cup to vibrate. These vibrations areincident on the receiver’s ear, and they hear the sound from the speaker cup.

Figure 3: Toy phone



You can try numerous such activities yourself to show that sound travels through solids. You can place your ear at one end of a long wooden or metallic table and ask your friend to gently scratch the other end of the table.

Figure 4: Sound can travel through solids

 

We find that sound can travel through wood or metal. In fact, sound can travel through any solid.

Can you think of more activities that show that sound travels through solids?

KEY MESSAGES 

Sound travels through solids

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

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Time: 15 min

ABL 2.2

12

LEARNING OBJECTIVE – Can sound travels through liquids?

Note to Instructor - These activities show how every sound you hear is produced because of vibrations.

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Bucket of clean water

1 per class/group

2

Bell

1 per class/group

Things to do N.A Safety Precautions Ensure that the water does not get into the ears of the students when trying to listen to the sound on the surface of water.

SESSION Link to known information/previous activity In the previous activity you learned that sound travels through solids, what about through liquids? Can you think of some things that you have noticed in the past to show you that sound travels or does not travel through liquids?

Procedure Take a bucket and fill it with clean water. Take a small bell in one hand. Shake this bell inside the water to produce sound. Make sure that the bell does not touch the body of the bucket. Place your ear gently on the water surface. This activity can be performed one per class and have all the students listen to the sound. Alternatively, it can be done in groups.

Figure 5: Sound travels through liquids

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UNDERSTANDING THE ACTIVITY Leading questions 1. Were you able to listen to the sound of the bell when you placed your ear close to the surface of water?

2. Do you think sound can travel through liquids?

Discussion and explanation Discussion Item 1: The following points are about how sound can travel through liquids.  The previous activity showed that sound travels through solids.  This activity, you could hear the sound of the bell from the surface of the water.  The vibrations caused by the bell were carried through the liquid and to the top of the surface of water. And hence you were able to hear the sound of the bell.  Hence we can say that sound travels through liquids.

KEY MESSAGES 

Sound travels through liquids

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

Time: 20 min

ABL 2.3 LEARNING OBJECTIVE – Does sound require a medium to travel?

Note to Instructor - These activities show how sound travels through air but not in vacuum

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Conical Flask

1 per class

2

Rubber tube

1 per class

3

Small Bell

1 per class

4

Pencil and cork

1 per class

5

Pump to suck air

1 per class

Things to do: Not Applicable Safety Precautions Handle all glass equipments with care.

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14

SESSION Link to known information/previous activity In the previous activity you learned that sound travels through liquids, what about through air? Can you think of some things that you have noticed in the past to show you that sound travels or does not travel through air?

Procedure  Take a conical or round-bottomedflask and a cork with two holes.  Tie a small bell to a pencil and insert it into one hole of the cork.  Insert a bent tube in another hole and attach a rubber tube to the other end of the bent tube.  Fix the cork in the mouth of flask.  Ensure that air does not leak from the flask  Now shake the flask. You hear the sound of ringing bell.  Suck the air inside the flask with help of rubber tube and create it vacuum inside the flask.  Again shake the flask.  Have the students listen to the sound of bell before and after the air was sucked out

UNDERSTANDING THE ACTIVITY Leading questions 1. Do you hear the sound of the bell when there was air in the flask?

2. Were you able to hear the sound of the bell when all air was sucked off the conical flask?

3. What do you infer from this activity?

Discussion and Explanation Discussion Item 1: The following points are about how sound can travel through air but not through vacuum.  As I speak to you, you are able to hear me speak. This is because the sound produced by me travels through the air around us and reaches you.  The same was the case with the experiment we just did. You were able to hear the sound of the bell when there was air in the flask.  This is because sound travels through air and also through walls of the flask.  But when the air was fully sucked out of the flask (creating a vacuum), we were unable to hear the sound of the bell.  From the previous two activities and this one, we can conclude that sound travels through solids, liquids and air (or gases).  However sound is not propagated through vacuum. Can you guess why? We will see this in the next activity.

KEY MESSAGES  

Sound waves can travel through all the three forms of matter - solids, liquids and gases Sound always requires a medium to propagate

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

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15

Time: 10 min

ABL 2.4 LEARNING OBJECTIVE – How does sound travel?

Note to Instructor - These activities show how sound a form of energy has the wave nature.

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Slinky

1 per class

2

Blank papers and pencil

1 per student

Things to do: Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity From the previous activities you have learnt that vibrations produce sound and sound requires a medium to propagate. Let us explore more about the nature of sound Procedure  Take a slinky spring.  Stretch it along a smooth surface of table.  Vibrate one end to and fro along the length of the spring, to send a longitudinal wave [refer to figure (a) below]. Do not create a transverse wave down the spring.

Figure 6: Transverse and Longitudinal Waves using a slinky

UNDERSTANDING THE ACTIVITY Leading questions 1. How do you think sound travels in various mediums?

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16 2. Can you draw a picture about how you think sound propagates? Draw the source of sound on your left and draw your ears on the right. Now, fill the gap with a picture that represents your imagination of the way the sound reached your ear.

Discussion and Explanation Discussion Item 1:Discuss the wave nature of Sound  Students draw different representations about how they think sound travels. For example: As straight lines, as music notes, as curved lines like waves, etc. For those who have drawn it as waves, tell them that they are close to the answer.  When an object vibrates, it sets the particles of the medium around it vibrating. Recall that matter is made of atoms or molecules, which are bound to each other.  The particles do not travel all the way from the vibrating object to the ear. A particle of the medium in contact with the vibrating object is first displaced from its equilibrium position. It then exerts a force on the adjacent particle. As a result of which the adjacent particle gets displaced from its position of rest.  After displacing the adjacent particle the first particle comes back to its original position. This process continues in the medium till the sound reaches your ear.  The disturbance created by a source of sound in the medium travels through the medium and not by transport of the particles of the medium.  A wave is a disturbance that moves through a medium when each particle of the medium sets neighbouring particle into vibratory motion.  The particles of the medium do not move forward themselves, but the disturbance is carried forward.  This is what happens during propagation of sound in a medium, hence sound can be visualised as a wave. Sound waves are characterized by the vibration of particles in the medium and are called mechanical waves.

Figure 7: Compressions and rarefactions

 

 

If you looked closely at the slinky you can see that, at any instant, some parts of the spring are pushed closer together (compression) and adjacent parts are pulled farther apart (rarefaction).

In the same way sound wave travels in air in the form of alternate compressions and rarefactions.

In some places the molecules of air are pushed together at slightly higher pressure (compression) and in adjacent places molecules are farther apart at slightly lower pressure (rarefaction).

Discussion Item 2:Discuss that sound is a form of energy You must have experienced this before. When an aircraft is speeding above your building or when you hear loud music being played in your neighbourhood, the glass windows start to vibrate.

Recall that energy is the capacity to do work.

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17 

Evidence that sound is a form of energy is found in the fact that sound can do work. A sound wave created in one location can cause the mechanical vibration of an object at a different location.

For example, sound can set eardrums in motion, make windows rattle, or shatter a glass.

KEY MESSAGES   

Sound is a form of energy Sound travels as mechanical waves In sound propagation, it is the energy of the sound that travels and not the particles of the medium

LEARNING CHECK Use the below topics to facilitate group discussion in class.

1. Why can’t we hear the sound of explosions on the sun?

Instructor notes: We cannot hear the explosions from the sun as sound cannot travel through a vacuum, and the sound would have to travel through empty space to reach the Earth.

2. Why do you think that sound might travel faster through liquids and solids than it does through air/gas?

Tip - think about how close particles are together?

The speed of sound depends upon the properties of the medium it is passing through. When we look at the properties of a gas, we see that only when molecules collide with each other can the condensations and rarefactions of a sound wave move about. So, it makes sense that the speed of sound has the same order of magnitude as the average molecular speed between collisions.Sound travels faster in liquids than in gases because molecules are more closely packed and stronglybound. Several ocean-dwelling animals rely upon sound waves to communicate with other animals and to locate food and obstacles. The reason that they are able to effectively use this method of communication over long distances is that sound travels so much faster in water.Sound travels fastest through solids. This is because molecules in a solid medium are much closer together and more strongly bound than those in a liquid or gas, allowing sound waves to travel more quickly through it.

TRY IT YOURSELF 

Come up with your simple activities that show that sound travels through solids, liquids and gases

INTERESTING INFORMATION Sound is extremely important to the survival of the dolphin species.

Dolphins have a very acute sense of hearing, which they use to communicate with one another, listen out for predators or threats in the area and find food.Vocally dolphins communicate using high-pitched clicking sounds and whistles

WEB RESOURCES Visualizing sound waves: http://www.youtube.com/watch?v=93DFanOXzL8 Virtual Museum: http://www.musicinventions.org/shepherd2010/shepherdindex.html http://whalesounds.com/home/index.html http://www.watchknowlearn.org/Video.aspx?VideoID=37512&CategoryID=2548 Agastya International Foundation. For Internal Circulation only.

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18

REFERENCES Figure 3:http://eagerbeavertoddler.blogspot.in/2010/03/networking-with-familiy-members.html Figure 4: NCERT Science Text Book Class VIII Figure 5: NCERT Science Text Book Class VIII Figure 6: http://strongphysics.wikispaces.com/ch26_kmlv Figure 7: http://share.ehs.uen.org/node/9430 Figure 8: http://www.physicsclassroom.com/class/sound/u11l1c.cfm http://www.teachengineering.org/view_activity.php?url=collection/cub_/activities/cub_energy2/cub_ene rgy2_lesson05_activity2.xml

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19

ABL 3 Properties of Sound Activity

Learning objective

Key messages

Time (min)

3.1

Frequency and Pitch

 

 

3.2

Audible and inaudible sounds





3.3

Amplitude and loudness

 

3.4

Noise, Music and Noise Pollution

   

Frequency or pitch is an important property of sound The number of oscillations or vibrations per second is called the frequency of oscillation.

The frequency is expressed in hertz (Hz) Higher the frequency, higher the pitch

15

Sounds of frequencies less than about 20 vibrations per second (20 Hz) cannot be detected by the human ear. Such sounds are inaudible.

Sounds of frequencies higher than about 20,000 vibrations per second (20 kHz) are also not audible to the human ear.

15

Larger the amplitude of vibration, 15 louder is the sound.

The loudness (intensity level to be more precise) is expressed in a unit called decibel (dB).

Unpleasant sounds are called 15 noise.

Excessive or unwanted sounds lead to noise pollution.

Noise pollution may pose health problems for human beings.

Attempts should be made to minimize noise pollution.

Total Time

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60 mins

20

ABL 3.1

Time: 20 min

LEARNING OBJECTIVE - Frequency and Pitch Note to Instructor - These activities help students understand some of the properties of sound such as frequency and pitch.

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Plastic Straws (drinking

1 per students

straws) 2

Scissors

2 per class

Things to do: Not Applicable Safety Precautions: Instruct students to handle scissors with care.

SESSION Link to known information/previous activity In the first activity when you were blind folded, you could still identify some of the sounds. You can recognize many familiar sounds without seeing the objects producing them. How is it possible? These sounds must be different to enable you to recognize them. Have you ever thought what factors make them distinguishable?

Procedure Have the students perform the below activity. Cut the end of a drinking straw into aV section. If you press your lips against thepart marked ‘L’, and blow, you should, witha bit of practice, be able to make the strawsound a musical note.

Figure 8: Cut Straw

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21

UNDERSTANDING THE ACTIVITY Leading questions 1. What do you think is causing the sound?

2. Cut pieces off the end of the drinkingstraw as you blow! How does the sound change?

Discussion and Explanation Discussion Item 1:The sound depends on the length of the straw  The straw works rather like a musical instrument, with theV section vibrating to cause the sound.  The sound is picked up by the air insidethe straw, which vibrates and causes a note that depends on the length of thestraw.  You noticed that the sound was not the same when the length of the straw was made shorter. We say that the pitch of the sound differs. The shorter the length of the straw, higher the pitch.

Discussion Item 2:Frequency/Pitch – an important property of sound.  In this discussion let us find out the reason for the variations in the sound due to the length of the straw  We have learnt that the to and fro motion of an object is known as vibration. Thismotion is also called oscillatory motion.  The number of oscillations or vibrations per second is called the frequency of oscillation. The frequency is expressed in hertz (Hz)  A frequency of 1 Hz is one oscillation per second.  It is this frequency that determines the shrillness or pitch of a sound. If the frequency of vibration is higher we say that the sound is shrill and has a higher pitch. If the frequency of vibration is lower, we say that the sound has a lower pitch.  For example, a drum vibrates with a low frequency. Therefore, it producesa low-pitched sound.  On the other hand, a whistle has a high frequency and therefore, produces a sound of higher pitch

Figure 9: Sound of varying frequency or pitch (Drum and Whistle)



In the case of the straw, the pitch increased as the length of the straw decreased.

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KEY MESSAGES    

Frequency or pitch is an important property of sound The number of oscillations or vibrations per second is called the frequency of oscillation.

The frequency is expressed in hertz (Hz) Higher the frequency, higher the pitch

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

Time: 20 min

ABL 3.2 LEARNING OBJECTIVE – Audible and inaudible sounds Note to Instructor - These activities discuss audible and inaudible sounds – Hearing Range

ADVANCE PREPARATION Material List Not Applicable Things to do N.A Safety Precautions N.A

SESSION Link to known information/previous activity In the previous ABL you have learnt about the frequency of sound. In this ABL let us learn about the range of audible frequencies.

Procedure Ask the students to perform this activity. Make a fanning movement with your hand near your ear as fast as you can.

UNDERSTANDING THE ACTIVITY Leading questions 1. How many times can you make your hand go back and forth per second as you fan?

2. Can you hear anything?

Discussion and explanation Discussion Item 1: The following points are about audible frequencies Agastya International Foundation. For Internal Circulation only.

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23     

In the activity you can feel the air near your ear but you won’t hear a sound because the moment of your hand is not fast enough and its frequency (thenumber of back and forth moves per second) is too low.

The human ear can pick up sounds between the frequencies of 20 Hz and 20000Hz.Such sounds are called audible.

Sound waves with frequencies below the audible range are termed “infrasonic” and those above the audible range are termed “ultrasonic”.

Some animals can hear sounds of frequencies higher than 20000Hz. Dogs have this ability. The police use high frequency whistles which dogs can hear but humans cannot The ultrasonic equipment familiar to us for investigating and tracking many medical problems works at frequencies higher than 20000 Hz.

KEY MESSAGES  

Sounds of frequencies less than about 20 vibrations per second (20 Hz) cannot be detected by the human ear. Such sounds are inaudible.

Sounds of frequencies higher than about 20,000 vibrations persecond (20 kHz) are also not audible to the human ear.

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

Time: 20 min

ABL 3.3 LEARNING OBJECTIVE – Amplitude and loudness Note to Instructor - These activities discuss another important property of sound, Amplitude .

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Toy drum and sticks

1 per class/group

Things to do Not Applicable Safety Precautions Not Applicable Agastya International Foundation. For Internal Circulation only.

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SESSION Link to known information/previous activity In the previous activities you learned about frequency, now let us learn about another important property of sound.

Procedure Display the toy drum. And beat the toy drum once or twice. If more number of drums are available you can distribute one per group and ask the students to perform this activity

UNDERSTANDING THE ACTIVITY Leading questions 1. What must be done to obtain a louder sound?

2. What is happening to the skin of the drum to get a loud sound?

3. You have learned about frequency/pitch. What must be done to obtain a higher pitched sound?

4. What is happening to the skin of the drum to obtain a higher pitch?

5. Does striking the drum more frequently produce a higher pitch/frequency?

Discussion and Explanation Discussion Item 1:What makes a sound louder?  In order to get a louder sound, you must beat the drum harder. o The loudness or softness of a sound is determined basically by its amplitude. o If we strike a drum lightly, we hear a soft sound because we produce a sound wave of less energy (amplitude). o If we hit the drum harder we hear a loud sound. Loud sound can travel a larger distance as it is associated with higher energy. o A sound wave spreads out from its source. As it moves away from the source its amplitude as well as its loudness decreases.  When the skin is hit hard, the amplitude of the vibrating skin increases and the sound heard is louder.  The frequency of the sound note can be increased by fastening the skin more tightly to the drum or by decreasing the thickness of the skin.  As the skin is fastened tightly, it produces more vibrations per second and hence the pitch increases.  In the case of a thinner membrane, it vibrates with a larger pitch or frequency because of the reduced mass.

Discussion Item 2:Frequency of sound is different from frequency of the drum beat.  A sound note is produced by beating the drum.  By beating the drum more frequently more number of notes are produced.However all these notes are of the same frequency.  The frequency of the sound note can be changed only by changing either the thickness of the skin or by changing the tension with which the skin is fastened.

Discussion Item 3:Pictorial representation of frequency and amplitude to help clarify the two different properties of sound  Objects of different sizes and under different conditions vibrate at different frequencies to produce sounds of different pitch.

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Chart 1: Sounds of differing pitch but same amplitude

Chart 2: Soft and loud sound but of the same frequency

 

The loudness or softness of a sound is determined basically by its amplitude.

Figure 12 shows the wave shapes of a loud and a soft sound of the same frequency.

KEY MESSAGES  

Larger the amplitude of vibration, louder is the sound.

The loudness (intensity level to be more precise) is expressed in a unit called decibel (dB).

Time: 20 min

ABL 3.4 LEARNING OBJECTIVE – Noise, Music and Noise Pollution Note to Instructor – This activity helps students distinguish noise and music.

ADVANCE PREPARATION Material List Not Applicable Things to do Not Applicable Safety Precautions Not Applicable Agastya International Foundation. For Internal Circulation only.

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SESSION Link to known information/previous activity: Not Applicable Procedure Have someone with a good voice and rhythm; sing a song in the class. Let the other students make a note of what they felt about the ‘sound’ produced.

Then, have the students chatter in class for few minutes. Ensure, it does not disturb the others in the surroundings. Now, let the students make a note of what they felt about this ‘sound’ produced in class.

UNDERSTANDING THE ACTIVITY Leading questions 1. Can you compare the notes you had written for the two types of sound that were produced?

2. Which one you thought was pleasant to hear?

Discussion and Explanation Discussion Item 1:Sounds that are pleasant, and those that are not!  When all the students speak together, it was very unpleasant for the ears.  Such unpleasant sounds are called noise.  However, when someone sings a song or plays a musical instrument, it sounds pleasant.  Such a pleasant sound is called music  However, a musical sound when becomes too loud, can become noise!

Discussion Item 2:Noise pollution  You already know about air pollution. Presence of unwanted gases and particles in air is called air pollution. Similarly, presence of excessive or unwanted sounds in the environment is called noise pollution.  Major sources are sounds of vehicles, explosions including bursting of crackers, machines, loud speakers etc. What sources in the home may lead to noise? Television and transistor radio in a high volume, some kitchen appliances, desert coolers, air conditioners,all contribute to noise pollution.  Presence of excessive noise in the surroundings may cause many health problems. Lack of sleep, hypertension (high blood pressure), anxiety, and many more health disorders may be caused by noise pollutions.  A person who is exposed to loud sound continuously may get temporary or even permanent impairment of hearing.

KEY MESSAGES    

Unpleasant sounds are called noise.

Excessive or unwanted sounds lead to noise pollution.

Noise pollution may pose health problems for human beings.

Attempts should be made to minimize noise pollution .

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

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27

ABL 4 Reflection of sound and Echo 4.1

Reflection of sound





4.2

What is an Echo?

 

4.3

Speed of Sound



 

4.4

Doppler Effect





Like light, sound gets reflected at 20 the surface of a solid or liquid and follows the same laws of reflection The directions in which the sound is incident and is reflected make equal angles with the normal to the reflecting surface Sounds that reflect off objects are echoes.

To hear a distinct echo the time interval between the original sound and the reflected one must be at least 0.1s.

10

Sound travels at different speeds 25 depending on the material through which it travels Echoes can be used to estimate the speed of sound At 00C the speed of sound in air is 330 m/s. At room temperature it is about 340 m/s.

There is an apparent change in frequency of a wave in motion due to relative motion of the source and observer.” This is known as Doppler effect Doppler effect sometimes called Doppler shift is so named because it was first explained by as Austrian physicist Christian Doppler in 1842.

15

Total Time

70 mins

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28 Time: 20 min

ABL 4.1 LEARNING OBJECTIVE – Reflection of sound ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Clock

1 per class/group

2

Cardboard tubes

2 per class/group

3

Hardboard/drawing board

1 per class/group

4

White sheet and pencil

1 per class/group

Things to do Construct a representative model using Fig 10.

Safety Precautions Not Applicable

SESSION Link to known information/previous activity We have learnt that sound travels in mediums. Let us now explore another interesting property of sound.

Procedure This activity can be performed in groups of four or like a demonstration in class based on the availability of the materials.  Take two cardboards tubes, arrange the tubes as shown in the figure below  Keep a clock near one end of one of the tubes and try to hear its sound through the other.  Ask the students to listen to the sound of the clock  Now place a sheet of hardboard near the ends of the tube as shown  Turn the cardboard tubes until the watch sounds loudest.  Measure the inclinations of the tubes with respect to the hardboard sheet.  Repeat this for different inclinations.

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Figure 10:Reflection of Sound model

UNDERSTANDING THE ACTIVITY Leading questions 1. Could you hear the sound of the clock clearly before placing the hardboard /drawing board?

2. At what angle was the sound of the clock heard clearly?

3. What can you infer from this activity?

Discussion and Explanation Discussion Item 1:Reflection of Sound  The sound could not be heard clearly before placing the hardboard.  The sound of the clock was heard clearly when both the tubes were equally inclined with respect to the hardboard. o Sound bounces off a solid or a liquid like a rubber ball bounces off a wall. o Like light, sound gets reflected at the surface of a solid or liquid and follows the same laws of reflection as you have studied in earlier classes. o The directions in which the sound is incident and is reflected make equal angles with the normal to the reflecting surface, and the three are in the same plane.  Sound like light is reflected at the surface of an object and obeys the laws of reflection.

KEY MESSAGES  

Like light, sound gets reflected at the surface of a solid or liquid and follows the same laws of reflection The directions in which the sound is incident and is reflected make equal angles with the normal to the reflecting surface

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

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ABL 4.2

Time: 10 min

LEARNING OBJECTIVE -What is an Echo?

ADVANCE PREPARATION Material List Not Applicable Things to do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity we have learned that some of the surfaces reflect sound. Now let us look at another interesting phenomenon of sound.

Procedure Have the students perform this activity. Stand infront of a large wall at a distance of 20 meters away. Clap once.

UNDERSTANDING THE ACTIVITY Leading questions 1. What happens when you clapped once?

Discussion and Explanation Discussion Item 1:What are echoes?  If you clap once, you listen sound of two claps, one after another.  Once a sensation of sound produced in human ear. It remains there for 1/10th of a second. If the same sound is heard after 1/10th of the second, we call it as an echo.  When you clap, you hear its sound directly at that instant. And the waves that travel towards wall will be reflected from the wall and reaches your ear after 1/10th of a second. So you hear again same clap sound.  Echo sounding is used by ships to find the depth of the sea and to detect submarines. It is also used by bats and dolphins that make noises and listen to the echoes to “see” their surroundings.

KEY MESSAGES  

Sounds that reflect off objects are echoes.

To hear a distinct echo the time interval between the original sound and the reflected one must be at least 0.1s.

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

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31 Time: 25 min

ABL 4.3 LEARNING OBJECTIVE - Speed of sound ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Metal rods

1 per class

2

Stopwatch

1 per class

Things to do Not Applicable Safety Precautions Handle metal objects with care. Ensure the students are not hurt.

SESSION Link to known information/previous activity We have learned that sound travels in different medium. How fast does it travel in air? Let us find out.

Procedure  Stand a measured 100 meters from a large wall.  Take two metal rods.  Bang them together and listen the echo.  Then try to bang in an even rhythm of bang-echo-bang-echo-bang………  At the same time you ask your friend to measure the time for 100 echoes starting from the first bang using stopwatch.

UNDERSTANDING THE ACTIVITY Leading questions 2. What are echoes?

3. How can you use the information about echoes to calculate the speed of sound?

4. What is the distance travelled by sound for each echoes?

5. How is speed calculated?

Discussion and Explanation Discussion Item 1:Calculating the speed of sound  Sound travels at different speeds depending on the material through which it travels  During the time from one bang to the next bang, the sound would have to go to the wall and back. i.e. a distance of 200 meters  In the time of 100 bangs and echoes, the sound could travel 200 x 100 = 20,000 meters.  Speed of sound is given by distance travelled by the time taken Agastya International Foundation. For Internal Circulation only.

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32

  

At 00C the speed of sound in air is 330 m/s. At room temperature it is about 340 m/s.

Speed of sound in water – 1500 m/s Speed of sound in steel – 6000 m/s

KEY MESSAGES   

Sound travels at different speeds depending on the material through which it travels Echoes can be used to estimate the speed of sound At 00C the speed of sound in air is 330 m/s. At room temperature it is about 340 m/s.

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

Time: 15 min

ABL 4.4 LEARNING OBJECTIVE - Doppler Effect ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Doppler Effect – Agastya

1 per class/group

Model 2

Dry Cells -2AA

1 per model

Things to do: Prepare to use the model. Open the lid of the plastic box and insert the two dry cells in the cell holder.

Safety Precautions Be careful when you swing the plastic box with the string. Secure it firmly with your hands.

SESSION Link to known information/previous activity In the previous set of activities you have learned about frequency/pitch. Let us find out about what happens to the pitch when the source of sound is in motion.

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33 Procedure Turn on the switch to hear the buzzer go off.Hold the string in your hand and start swinging the box in a horizontal plane.

Figure 11: Doppler Effect

UNDERSTANDING THE ACTIVITY Leading questions 1. As the buzzer moved towards you, how did it sound?

2. As the buzzer moved away from you, did the buzzer sound the same?

Discussion and Explanation Discussion Item 1:Discuss about an important phenomenon of sound- Doppler effect  You must have experienced this yourself. When an ambulance passes by you, you must have felt the pitch of the siren increase as the ambulance came towards you. And the pitch decreases abruptly once the ambulance moved away from you.  When there is a relative motion between the source of sound and an observer, the apparent pitch of the sound heard by the observer is different from the actual one. This is known as Doppler Effect.  This effect was first investigated by an Austrian Physicist J.C Doppler in 1842.  As the sound moves away from the observer, the waves are spread apart and hence the pitch will be lesser.  A similar observation is made even when an observer approaches or recedes from stationary horn.  There is an apparent change in frequency of a wave in motion due to relative motion of the source and observer.

KEY MESSAGES  

There is an apparent change in frequency of a wave in motion due to relative motion of the source and observer.” This is known as Doppler effect Doppler effect sometimes called Doppler shift is so named because it was first explained by as Austrian physicist Christian Doppler in 1842.

LEARNING CHECK 1. Would you be most likely to hear an echo in a room that is A. Empty (Answer) B. Filled with drapes, curtains, carpet and furniture C. Contains one couch D. None of the above 2. The harder you hit a drum...

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34 B. the higher the pitch of the sound C. the lower the pitch of the sound D. None of the above 3. Suppose you have four bottles. One is empty, one is 1/4 full of water, one is about 2/3 full of water and one is nearly full. Predict what difference, if any, there will be if you blow across the top of each bottle. Give reasons for your predictions

Answer: The pitch of the sounds will be different for each bottle because the amount of vibrating air column length varies for each bottle 4. As you tighten a drum skin, the sound made when you hit it...

A. gets lower in pitch B. gets higher in pitch (Answer) C. stays the same D. None of the above 5. As you tighten a string, the sound made when you pluck it...

A. gets lower in pitch B. gets higher in pitch (Answer) C. stays the same D. None of the above

TRY IT YOURSELF Make your own ear trumpet and megaphone. <3 Funnel and tube activity – Included from science centre>

INTERESTING INFORMATION   

When traveling through water, sound moves around four times faster than when it travels through air.

The loudest natural sounds ever made on Earth are probably gigantic volcanic eruptions, such as the explosions of the island of Krakatoa.

The BA-Aerospatiale Concorde is of the supersonic passenger plane to fly faster than sound, at 2100 kph.

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Figure 8: British Airways Concorde in 1986



In the recording studio any stray sound is a nuisance. So the walls, ceilings and floors are covered with sound-absorbing substances, such as wavy-surfaced tiles and thick carpets. There is a continuing search for 'acoustically dead' materials that absorb all sounds

WEB RESOURCES  

http://www.youtube.com/watch?v=26qvYE-w8Eo http://www.teachengineering.org/view_activity.php?url=collection/cub_/activities/cub_energy2/ cub_energy2_lesson05_activity2.xml

REFERENCES Figure 9: http://www.deakin.edu.au/arts-ed/education/sci-enviro-ed/early-years/pdfs/sound.pdf Figure 10, 11, 12 - NCERT Science Textbook Class VIII and IX Figure 14: http://www.tarangscientificinstruments.com/products-waves-sound.html Figure 16:http://en.wikipedia.org/wiki/File:British_Airways_Concorde_G-BOAC_03.jpg http://library.thinkquest.org/26585/interestingfacts.htm NCERT Science Textbooks – Class VIII and Class IX http://www.bbc.co.uk/bitesize/ks2/science/physical_processes/sound/quiz/q75676573/ http://www.teachengineering.org/view_activity.php?url=collection/cub_/activities/cub_energy2/cub_ene rgy2_lesson05_activity2.xml http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/waves/soundandlightrev1.shtml

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36

ABL 5- How do we hear sounds?

Activity

Learning objective

Key messages

Time (min)

5.1

How do we hear?

ď&#x201A;§ ď&#x201A;§

We are able to hear sounds with 15 the help of our ears The eardrum vibrates when sound waves strike it. The cochlea converts the vibrations into electrical impulses and sends it to the brain.

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ABL 5.1

Time: 15 min

LEARNING OBJECTIVE:How do we hear?

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Chart of the human ear

1 per class

Things to do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity We have learned that sound travels as mechanical waves. In this section, let us study about how these waves reach the ear and how we hear sounds.

Procedure Use the chart of the human ear to explain important each part of the human ear that is responsible in the task of hearing

UNDERSTANDING THE ACTIVITY Leading questions 1. Which important part of your body is responsible for the sense of hearing?

2. How do we hear sounds?

3. How does our ear function?

Discussion and Explanation Discussion Item 1: The following points describe how the ear functions in order for us to be able to hear sounds The ear plays an important role in hearing. In general, the ear consists of three major sections: the outer, middle and inner ear. Sound is collected by the outer ear and funneled down the ear canal (outer ear). The sound vibrations cause movement of the eardrum and a chain of three tiny bones connected to it (middle ear). The middle ear system serves to intensify the energy of the sound vibrations and delivers them to the cochlea (inner ear). Inside the cochlea are thousands of tiny hair-like cells that connect to fibers of the hearing (acoustic) nerve. Sound vibrations entering the cochlea cause a wave to travel through the fluidfilled organ of hearing. This wave causes movement of the hair cells, which then generate electro-chemical signals, which travel through the acoustic nerve to the brain where they are recognized as sounds.

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Figure 12: Anatomy of the Human Ear

The Outer Ear 1) Outer ear (pinna). This is the part of the ear that we can see. The pinna acts as a sound collector and helps channel sound down the ear canal.

2) Ear canal. Ear wax (cerumen) is produced in the ear canal. The wax serves as a protective mechanism and helps to keep the ear canal clean.

3) Eardrum (tympanic membrane). The eardrum is sonamed because it functions much like the head of a drum, vibrating when sound waves strike Figure 13: Outer Ear

it.

The Middle Ear

Figure 14: Middle Ear

The middle ear consists largely of empty space. 4--6 Ossicular Chain. This chain of 3 bones contains the smallest bones in the body. The Malleus (4) is attached to the eardrum. The middle bone is called the Incus (5) and the last bone is called the Stapes (6). The Stapes is connected to the oval window--a membrane leading into the cochlea. Sound vibrations striking the eardrum are made more intense by the piston-like action of the ossicular chain.

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39 7) Eustachian tube. This tube leads from the middle ear space to the back of the throat and serves to equalize the air pressure on both sides of the eardrum. Unequal pressure is responsible for the "plugged" feeling you sometimes get when driving into the mountains or riding in an airplane. When the Eustachian tube opens you feel a "pop" as the pressure is equalized and your ear feels "normal" again.

The Inner Ear

Figure 15: Inner Ear

8) Balance (vestibular) canals. The vestibular system in your ear is part of the balance system for your body. The system contains sensory cells that provide information about the position and motion of your head.

9) Cochlea. The cochlea is shaped like the shell of a snail and contains the sensory organ of hearing. It is encased in the temporal bone, the hardest bone in the skull. The anatomy of the cochlea is very complex and the function of this marvelous organ is still not completely understood. The cochlea is coiled into approximately 2.5 turns and contains 3 fluid-filled compartments separated by Reisner's membrane and the basilar membrane.

KEY MESSAGES ď&#x201A;§ ď&#x201A;§

We are able to hear sounds with the help of our ears The eardrum vibrates when sound waves strike it. The cochlea converts the vibrations into electrical impulses and sends it to the brain.

LEARNING CHECK Draw arrows to connect the words to the correct part of the ear.

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40 Earflap or pinna Semi-circular canals

stirrup, anvil and hammer bones

Auditory Nerve

Cochlea

Eardrum

Ear canal

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TRY IT YOURSELF Try to make a model of the eardrumhttp://nodoubtlearning.com/2012/06/04/model-eardrum/ Materials Plastic cup, balloon, rubber band, and a few grains of rice Procedure 1. 1. Cut the spout off of a balloon, stretch it out flat and tightly over a plastic cup, and secure it with a rubber band (keeping the balloon tight!).

2. 2. Shout, clap, or lean in really closely to make a loud deep noise and watch rice bounce around on the balloon from the vibrations, similar to the way your eardrum works

Figure 9: Model of eardrum

How does it Work?

When your voice produces sound waves, they vibrate the balloon similar to the way your eardrum vibrates when it interacts with noise.

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42

INTERESTING INFORMATION Have you noticed the ears of the animals?

Elephant Animals move their ears to collect sounds and that some have large ears to help collect the sounds like an ear trumpet. Ear trumpets are tubular or funnel-shaped devices that collectsound waves and lead them into the ear. They serve as hearing aids, resulting in a strengthening of the sound energy impact to the eardrum and thus a better hearing for a reduced or decreased hearing individual.

You must have noticed people cupping their hand around their ear like a larger ear and listening to the change in a sound. Unlike animals we cannot move our ears. We have to move our whole head. The fact that we have two ears helps us to decide which direction the sound is coming from, because the sound wave reaches one ear before the other. It is important for many animals to hear sounds clearly and to know where the sound is coming from in order to escape from predators.

WEB RESOURCES http://www.sciencekids.co.nz/videos/humanbody/ear.html Agastya International Foundation. For Internal Circulation only.

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REFERENCES http://www.hamiltontrust.org.uk/science/sessions/Upper_Key_Stage_2/Science_Y5__Sound/Y5_Sound/195 http://www.tes.co.uk/teaching-resources/ Elephant picture:http://www.seaworld.org/animal-info/info-books/elephants/physical-characteristics.htm Figure 21-23: http://kidshealth.org/parent/general/eyes/cochlear.html Figure 24: http://teamhearing.org/blogs/?tag=ear-trumpets

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ABL 6 Musical Instruments Activity

Learning objective

Key messages

Time (min)

6.1

How do stringed



instruments produce  sound?



6.2

How do Wind (pipe)



Instruments produce



sound? 

6.3

How do Percussions



Instruments produce  sound?

Stringed instruments have strings that vibrate at their own natural frequency.

The natural frequency of a string can be increased by o Shortening the length o Increasing the tension Using the lighter string

20

Vibrating air is the basis of wind instruments.

The pitch of the sound produced depends on the length of the air columns Smaller the air column, higher the vibrations and hence higher the frequency or pitch.

20

Vibrating rods, plates and bells are good examples of percussion instruments.

Longer rods produce low pitch and the shorter ones the higher pitch

20

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ABL 6.1

Time: 20 min

LEARNING OBJECTIVE â&#x20AC;&#x201C; How do stringed instruments produce sound?

Note to Instructor - This activity makes students to create a small toy guitar and learn to apply the concepts of frequency and amplitude.

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

Shoebox or cardboard box

1 per group

2

Rubber bands of various sizes

A set per group

and lengths 3

Pencils

2 per group

4

Scissors

1 per group

Things to do Not Applicable Safety Precautions Handle sharp objects such as scissors with care.

SESSION Link to known information/previous activity In the previous set of activities, we have learned that sound is produced due to vibrations. Musical instruments can be broadly classified under one of the following: 1.

Strings 2.

Winds 3.

Percussions These terms apply to the material part of the instruments set into vibration when the instrument is played, or to the method by which it is set into vibration.

In this ABL let us look at stringed instruments.

Procedure Show some of the pictures of stringed instruments or ask the children to name some of them that they are familiar with.

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Chart 3: Stringed Instruments

Distribute the materials to the groups and ask them to use it to make a toy guitar Guide them using the instructions below to make one.

Cut out a circle on the shoebox. Wrap the rubber bands around the shoebox lengthwise and position them about an inch apart. Both rubber bands should stretch over the hole.Slide the pencil under the rubber bands andmove it to the end of the box away from the hole.

Observe the sound produced by plucking each rubber band Slide the pencil an inch toward the lid and observe the sound.

Pluck the string harder and observe the sound.

Figure 10: Shoebox Guitar

UNDERSTANDING THE ACTIVITY Leading questions 1. What does the natural frequency of string of these instruments depend on?

2. What can be done to produce sounds of higher and lower pitch?

3. What can be done to produce louder or softer sounds?

Discussion and Explanation Discussion Item 1: Stringed instruments and how to modify the loudness and pitch of such instruments  The diagrams show some string instruments. They make sounds because each string vibrates at its own natural frequency.  The natural frequency of a string can be increased by o Shortening the length o Increasing the tension o Using the lighter string 

Plucking the rubber bands on the shoebox guitar causes them to vibrate.

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47 

This vibration in turn produces sounds. The pitch of the sound will vary depending on the mass, length and tension (tightness) of the rubber band.



In general, the thicker the rubber band, the lower the pitch and the longer the rubber band, the lower the pitch. This is because thicker rubber bands have more mass than thinner ones and longer rubber bands have more mass than shorter ones. The higher the mass, the slower the rubber band will vibrate.

 •

Slow vibrations produce low pitches or frequencies, and fast vibrations produce high pitches or frequencies.

Plucking the strings harder makes louder sounds.

KEY MESSAGES  

Stringed instruments have strings that vibrate at their own natural frequency.

The natural frequency of a string can be increased by o Shortening the length o Increasing the tension o Using the lighter string

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

Time: 20 min

ABL 6.2 LEARNING OBJECTIVE – How wind (pipe) instruments produce sound?

Note to Instructor - This activity makes students to create a simple wind musical instrument and learn to apply the concepts of frequency and amplitude.

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

4 test tubes along with stands 1 set per group

2

Table

1 per group

3

Stick

1 per group

4

Beaker of clean water

1 per group

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48 Things to do N.A Safety Precautions Handle glass items with care

SESSION Link to known information/previous activity In the previous activity you saw how stringed instruments produce sound. Now we will look at wind instruments.

Procedure Show some of the pictures of wind (pipe) instruments or ask the children to name some of them that they are familiar with.

Chart 4: Wind (pipe) instruments

Distribute the materials to the groups and ask them to perform the below activity.

Set up a row of test tubes. Fill then with different amount of water, so that the length of air is different in each tube.Blow gently across the top edge of each tube.

UNDERSTANDING THE ACTIVITY Leading questions 1. What do you observe when you blow air at the surface of the test tubes?

2. Were the sounds produced the same with all the testtubes?

Discussion and explanation Discussion Item 1: What does the sound produced depend on?  Wind (pipe) instruments make a sound because the air inside the pipe is made to vibrate and resonate at its natural frequency  The test tube with the smallest amount of air should give the highest pitch when you blow it  When you blow, the air inside the bottle vibrates and the smaller the amount, Agastya International Foundation. For Internal Circulation only.

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49 the faster the vibrations.

KEY MESSAGES   

Vibrating air is the basis of wind instruments.

The pitch of the sound produced depends on the length of the air columns Smaller the air column, higher the vibrations and hence higher the frequency or pitch.

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

Time: 20 min

ABL 6.3 LEARNING OBJECTIVE -How percussion instruments produce sound?

Note to Instructor - This activity makes students create a simple xylophone learn to apply the concepts of frequency and amplitude.

ADVANCE PREPARATION Material List S.NO

Material

Quantity

1

1 set per group

2

5 Wooden rods of varying lengths Rubber or Wooden stick

3

Rubber Bands

A pair per group

4

Cardboard box (base support) 1 per group

1 per group

Things to do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity you saw how wind instruments produce sound. Now we will look at percussion instruments.

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50 Procedure Show some of the pictures of percussion instruments or ask the children to name some of them that they are familiar with.

Chart 5: Percussion Instruments

Distribute the materials to the groups and ask them to make a simple xylophone as shown below.

Chart 6: A simple xylophone with wooden rods

UNDERSTANDING THE ACTIVITY Leading questions 1. What do you observe when you hit on the wooden rods?

2. Is the sound produced by each rod the same or different?

Discussion and Explanation Discussion Item 1: Percussion instruments and how to modify the loudness and pitch of such instruments  Vibrating rods, plates and bells are good examples of percussion instruments.  Longer rods, means more medium hence less vibrations and hence produce low pitch  While shorter rods means less medium to propagate, hence more vibrations so higher pitch Agastya International Foundation. For Internal Circulation only.

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KEY MESSAGES  

Vibrating rods, plates and bells are good examples of percussion instruments.

Longer rods produce low pitch and the shorter ones the higher pitch

LEARNING CHECK A group of students performed the below activity.

Can you now answer the below questions based on this activity?

1. What vibrates to produce sound when you tap the bottle A. Water (Answer) B. Air column C. Stick D. None of the above 2. What vibrates to produce sound when you blow across the bottle?

A. Water B. Air column (Answer) C. Stick D. None of the above 3. Blow across each bottle and listen to the sounds produced I. Which bottle had the highest pitch?

The bottle with the least amount of air will have the highest pitch (True or false) II. Which bottle had the lowest pitch?

The bottle with the most amount of air will have low pitch (True or false) Answer: Both are true 4. When material vibrates slower, it produces a lower sound. In both cases the lower sound was produced by having the ___ (most/least) amount of vibrating substance.

Answer: most

TRY IT YOURSELF  

Try to make your own musical instrument from some of the easily available materials found in your house/school.

From your teachers/newspapers/communities find out about some of our famous musicians and the instruments they play.

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52 

Arrange a concert with your classmates and play some of instruments that you have created yourself. Post the concert, discuss about the various techniques you used to vary the pitch and loudness of the sound produced by your instrument

INTERESTING INFORMATION 



Humans were making musical instruments to produce sounds 20,000 years before the wheel and axle were invented! Among instrument builders, perhaps Antonio Stradivari is the most famous.

Between 1667 and 1730 Stradivari built violins in the small town of Cremona, Italy. A violin’s sound is rich and complexbecause vibrations of its wooden parts create a unique blend of frequencies.Stradivari worked tirelessly trying different woods and different varnishes, searching for the perfect sound. Over time he developed a secret formula for varnish, and special ways to carve and treat the all-important vibrating parts of the violin. In the 300 years since Stradivari, no one has figured out how he did it. Today, a Stradivarius violin is the most highly prized of all musical instruments. Its rich sound has never been duplicated.

Indian Musicians Tirumakudalu Chowdiah (1895 - 19 January 1967) was a violinmaestro from India Chowdiah designed the seven-stringed violin to ensure that the accompanist could match the vocalist (the need for this was felt especially in the early and mid-20th century when no amplification devices were available). He was known as Pitilu Chowdiah - Pitilu (fiddle) being the word for violin in South Indian languages such as Kannada. As he hailed from Tirumakudalu Narasipura near Mysore, so he is also known as Mysore T. Chowdiah.

Pandit Ravi Shankar, an instrumentalist who plays the sitar, was born on the 7th of April 1920 in Benares. His original name was Robindra Shankar. Pandit Ravi Shankar is largely responsible for taking Indian classical music to the West, giving it the global audience it enjoys today.

The Late Ustad Allarakha Khan was one of the country’s leading tabla maestros and was instrumental in establishing the tabla as a solo instrument. Ustad Allarakha Khan was born on the 29th of April 1919 in the Ratangadh of the Punjab.

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53 Ustad Amajad Ali Khan is a distinguished instrumental artist of the Sarod instrument. Ustad Amjad Ali Khan was born on the 9th of October in 1945 to a family that had tremendous musical tradition.

Ustad Bismillah Khan is a maestro of the wind instrument known as the shehnai A private man who believes that musicians should be heard and not seen. Ustad Bismillah Khan was born on the 21'st of March 1916. His family had been the court musicians of the princely state Dumraon. He played on the first day of Dussehra in the Kashi Vishwanath Temple for many years, was instrumental in keeping the peace in Banaras on more than one occasion, it said that the goddess Saraswathi sat on his shehnai!

Pandit Hari Prasad Chaurasia is a renowned player of the flute. His name means "Blessings of the Lord", a fitting name for a gifted man. Born to a family that had little to do with the music (his father was a distinguished wrestler and had similar aspirations for his son!)

Pandit Shiv Kumar Sharma was born on the 13th of January 1938 in Jammu, in the state of Jammu and Kashmir. Pandit Shiv Kumar Sharma is a unique artist, for he has received training in vocal, percussion and instrumental music. He has however specialized in playing the santoor as his father Pandit Umadutt Sharma wanted him to promote the instrument, a task Pandit Shiv Kumar Sharma has been extremely successful in doing. Pandit Shiv Kumar Sharma entered the classical music scene very early, beginning with training as a vocalist at the age of five and going to learn the Tabla, Sarod, Violin and Harmonium. Pandit Shiv Kumar Sharma began learning the Santoor from his father when he was fourteen years old. Pandit Shiv Kumar Sharma did some considerable reengineering of the santoor to make it more suitable for classical Indian music. People who doubted the santoor's capabilities were soon amazed after they heard the performances of Pandit Shiv Kumar Sharma.

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54 Ustad Zakir Hussain is a distinguished tabla maestro. The son of the legendary Alla Rakha he has continued the fine work started by his father and has consolidated the position of the tabla as a solo instrument. He was born on -. A child prodigy he learnt how to play the instrument very early in life and was already doing tours when he was only twelve years old. He has performed all over India and the world and has also been involved in composing music, especially fusion. His first solo release Making Music (1987) was the result of his efforts to fuse western and Indian music.

WEB RESOURCES http://www.youtube.com/watch?v=ZjAXR-jwviM http://www.youtube.com/watch?v=65caEmmjsYU

REFERENCES Figure 26: http://www.enchantedlearning.com/crafts/Boxguitar.shtml Figure 28: http://www.infovisual.info/04/012_en.html Figure 29:http://www.kiwicrate.com/shop/making-music.html http://www2.rps205.com/Parents/Academics/Learning/Science/Documents/PhysicsFirstTextbook/ Chapter21.pdf http://en.wikipedia.org/wiki/Wind_instrument http://en.wikipedia.org/wiki/Percussion_instrument http://en.wikipedia.org/wiki/String_instrument http://www.middletownschools.org/uploaded/Curriculum/Curriculum_Office/Files/Gr_5_Sound.pdf http://library.thinkquest.org/C006203/cgibin/stories.cgi?article=musicians&section=music/&frame=parent http://en.wikipedia.org/wiki/File:T_Chowdiah.jpg

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