1. Sound Junior Science: Physics

2. Revised Science Syllabus Extract
Main Topic
Sub-topics
3B5 Sound
transmission of sound
speed of sound
vibrations and sound
3B6 Reflection of sound
Hearing
reflection of sound
echoes
sound detection in the ear
sound levels
hearing protection

3. Learning Outcomes for 3B5 and 3B6
On completion of this section, students should be able to
OP40 show that sound is a form of energy, and understand that sound is produced by vibrations
OP41 show that sound transmission requires a medium and echoes are reflected sound

4. Learning Outcomes for 3B5 and 3B6
On completion of this section, students should be able to:
OP42 understand that the ear detects sound vibrations and that exposure to very loud sounds can cause damage to the hearing
OP43 recall that the speed of sound is less than the speed of light
OP44 explain the time lag between seeing and hearing the same event

5. Equipment and Resources
Shatter resistant rulers
Bell jar, sound source – alarm clock, vacuum pump

6. Can you guess what these sounds are?
Introduction
Start Introduction in a dramatic fashion….by informing the students that we will be investigating a physics topic today that has the ability to make us happy, sad, confused, dance, shout, groan, communicate, can give us a pain, can damage certain parts of our anatomy if we are exposed to too much of it and is something we usually take completely for granted until there is……..stop for a few seconds and whisper the word “silence” – then ask “what has just happened”………. Wait for responses……and depending on what they say….call for “hush” and say “I stopped making sound” and play the title of the first slide.
Start playing the first sound and ask the students to write down what they think the sound is? Ask the students to volunteer their answers.
Explain that we interpret the sound we hear by relating it to what we know already in the same way that we learn about new concepts by relating them to what we know already – and because most of us have probably never heard a Beluga whale or a shrimp make sound we might think the first sound is a chainsaw and the second - dripping water or a fire – so they must bear that in mind at all times.
Inform the students that over the next two lessons we will be investigating sound, finding out what sound is, how sound is created, how sound travels, the speed of sound, how we hear sounds, how we make sound, how we use sound and how exposure to very loud sounds can damage our hearing.
Beluga Whale
Shrimp

7. SOUND What is sound? Sound is a form of energy
Plat the titles of slide and first animation.
Ask the students how they would describe sound? What is sound?
Show first text box and reiterate sound is a form of energy.
Ask them to recall the definition of energy: as the ability to do work…..and the ability to be converted into other energy forms.
Show second text box.
Ask them to describe any examples of sound being able to do work such as move objects?
Ask them to describe what they would observe if I left a glass of water on top of a speaker playing very loud music………and determine what energy conversion is taking place?….
Dissolve text and ask the students again - what is sound?
Sound energy can be converted into other energy forms

8. Sound energy Sound energy Kinetic Energy
Ask the students if they can give an example of sound energy doing work to the extent that it can break something?
And if so, what energy conversion is taking place.
Remind them they may have seen cartoon clips of an opera singer breaking a pane of window glass with their voice.
Show the movie by clicking and point to the sound meter which is measuring the sound levels produced by the speakers beside the glass.
Ask the students to recall the description of Kinetic energy – the energy that is stored in a body that is moving. Ask the students to explain in their own words what is happening as the speakers are playing the sound which eventually breaks the glass.

9. Sound energy (contd.)
Sound energy can be converted into other energy forms
Sound energy
Electrical energy
Show text 1 and 2.
Ask the students if they can think of another common example of sound energy being converted into other energy forms. Remind them that they probably all have experience of sound energy conversions in different ways many times every day.
Show text 3.
Explain using the hyperlink – click on the animated phone - how a telephone works and bring the students attention to the energy conversions from sound to electrical energy.
Mention that the same energy conversion is taking place in a microphone if they have experience of using one for singing – the sound produced by our voices is converted to electrical energy in the microphone and amplified.

10. Sound is created when objects vibrate
How is sound created?
Sound is created when objects vibrate
Show title of slide.
Ask if any of the students play an instrument? And if so how is sound created by each instrument?
Ask the students how is sound created in a guitar string, a drum, a saxophone and by the voice. Reiterate the word Vibrations and Show text 2 and animation.
Give each pair of students a shatter resistant ruler. Ask them to put the rulers on the edge of the desk and give each pair an opportunity to ‘play’ the ruler - one person holds one end and the other ‘twangs’ the other end of the ruler. Ask the students what do they observe/hear when the rulers are ‘twanged’.
Explain that the rulers vibrate and cause the air to vibrate next to them. We can hear the sound produced.
Ask the students to vary the length of the ruler sticking out over the edge of the desk and describe the difference – the longer the ruler sticks out over the edge of the desk the lower the pitch of the sound is. Allow the students 2 minutes to play with their rulers and then ask them to put them away.

11. Vibrations Sound is produced by vibrations of the air molecules
A sound wave is just a moving pattern of changes in air pressure
Explain using the animation that the vibrations produced by the rulers changes the air pressure around it by pushing surrounding air particles out and then pulls them back in. These particles then push and pull the particles next to them, passing on the energy and pattern of the sound. In this way, sound can travel long distances through the air as a sound wave.

12. What is a sound wave? Sound wave Vibrating ruler Compression Pressure
Rarefaction
Sound is caused by vibrations of the air molecules. A sound wave is produced as the air is pushed together at high pressure (compression) and pulled apart at low pressure (rarefaction) by the vibrating ruler. These changes in pressure are passed through the air over a period of time in the form of sound waves.
The vibrations travel through the air to our ears.
Ask the students if they can give an example of another form of wave that moves like a sound wave.
Time

13. Transmission of sound
Sound requires a medium in order to be transmitted
Sound can be transmitted through a solid, liquid or gas
Sound cannot travel in a vacuum
Show title of slide and ask the students what is the medium that my voice is travelling through. The ability of sound to travel through different media is called the transmission of sound. Ask the students what would happen if I was standing in the hallway trying to speak through the wall and closed door.
Ask a student to step outside the door, tell her to repeat “Sound requires a medium in order to be transmitted” in a low whisper first and then getting progressively louder, close the door and call her back into the classroom when we can hear her words.
Explain that because sound is produced by the vibrations of particles, it cannot travel from one place to another unless there is some material in between just like a mexican wave cannot occur if people do not stand up and sit down but the people do not move with the wave.
Show second text and explain that the medium can be a solid liquid or gas e.g. the air. Ask the students how have we proved that sound travels through a solid in the last few minutes.
Ask the students to use the knowledge gained so far to think of a place where there is no sound and why is there no sound there.

14. Non-mandatory experiment to show Sound needs a medium in which to travel
Explain to the students that we are going to do an experiment to prove that sound needs a medium in which to travel and ask if they have any ideas how we could do this.
If they are not presenting any ideas provide them with the list of materials: bell jar, attachment to vacuum pump and a ringing alarm clock and ask again. Show the students the set up on the photograph and explain the sequence of events and then get the students to work in pairs and carry out the experiment.
Ask the students to record their observations/results and form a conclusion:
Sound requires a medium in which to travel.

15. What are echoes? Sound can be reflected off surfaces
Echoes are sounds that are reflected from a surface
Sound reflection can be used to calculate distance
Ask the students if they have ever stood in an empty street with tall buildings or near a cliff face and shouted. What happens? Show first text.
Explain that when you shout, you produce a sound wave that travels to the cliff face, the cliff face deflects the air-pressure energy of the sound wave so that it begins moving in the opposite direction, heading back to you and you hear your echo. Show second text.
In an area where atmospheric air pressure and air composition is constant, sound waves always move at the same speed. If you knew the speed of sound in the area, and you had a very precise stopwatch, you could use sound to determine the distance across to the cliff face by measuring the amount of time it takes for the echo to return.
Example: if it takes 0.5 seconds for the echo to return the distance can be found using
d = v x t
d = (speed of the sound wave ) x (0.5 refers to round trip)
= 85m

16. How do bats use sound? Echolocation
Show the title if the slide and inform the students that bats and many other animals use the fact that sound can be reflected to locate themselves and locate prey.
Ask the students to work in pairs for 2 minutes and determine how a bat might use this property of sound to find a bug for dinner.
Show the animation of the bat and explain echolocation.
Echolocation is how many animals (e.g. whales, dolphins, bats) use sounds to locate objects (such as prey) and to orient themselves.
Bats make sounds the same way we do, by moving air past their vibrating vocal chords.
In the case of most bats, the echolocation sound has an extremely high pitch -- so high that it is beyond the human hearing range. But the sound behaves the same way as the sound of your shout. It travels through the air as a wave, and the energy of this wave bounces off any object it comes across. A bat emits a sound wave and listens carefully to the echoes that return to it. The bat's brain processes the returning information the same way we processed our shouting sound using a stopwatch and calculator. By determining how long it takes a noise to return, the bat's brain figures out how far away an object is.
The bat can also determine where the object is, how big it is and in what direction it is moving. The bat can tell if an insect is to the right or left by comparing when the sound reaches its right ear to when the sound reaches its left ear: If the sound of the echo reaches the right ear before it reaches the left ear, the insect is obviously to the right. The bat's ears have a complex collection of folds that help it determine an insect's vertical position. Echoes coming from below will hit the folds of the outer ear at a different point than sounds coming from above, and so will sound different when they reach the bat's inner ear.

17. What is the speed of sound?
Speed of sound differs in different materials
Speed of sound in air at average temperatures and average pressure is approximately 340m/s
Play title and animation.
Ask the students to recall how we investigated the transmission of sound in the first lesson by asking a students to step outside the door. Ask what did that investigation prove? Sound requires a medium in order to be transmitted. Now ask does sound travel through all media at the same speed?
Show first text
Ask the students what is the factor which determines the speed of sound through different media - density
Show second text and animation

18. Speed of sound (contd.)
Sound does not travel through all materials at the same speed
Sound travels through water at approximately 1500m/s
Sound travels through iron at approximately 6000m/s
Show title and first text.
Ask the students to recall what they notice if they are swimming underwater in a pool or in the sea. Sounds always appear louder/closer because the speed of sound in water is 5 times faster than it is in air.
Sound travels 340 meters per second (m/s) in air and approximately 1500m/s in water.
Sound travels even faster through metals – why? Show third text.

19. The speed of sound and the speed of light
Speed of sound is much smaller than the speed of light
Speed of sound
350m/s
Speed of light
m/s
Show the title of the slide and ask the students which is faster sound or light?
Show 1st text.
Ask the students if they can give an example of a common event where they observe that the speed of sound is less than the speed of light. Play movie by clicking on photo.
Show text 2 and 3.
Ask them what they usually do when they hear thunder and see lightening – count seconds.
Ask them why do they count seconds - what information does this provide – Information on how far away the lightening is….each second is a distance of approximately 350m so we can calculate the distance because we know the speed of sound and the number of seconds it has taken to reach us.
Calculate the distance by counting the seconds

20. Seeing an event before we hear it
Fireworks
Waves crashing on a beach in the distance
Ask the students if they can provide other common examples which illustrate that the speed of sound is less than the speed of light and where we consequently see an event before we hear it.
Show the students the text and animations.

21. How do humans create sound?
Sound is produced by air rushing from your lungs past your vibrating vocal chords
Recap on how sound is created by asking the students how we humans create sound.
Show text and animation.
These vibrations caused fluctuations in the rushing air, which formed a sound wave

22. How do we hear sound?
The vibrations travel through the air to our ears
Our eardrums vibrate with the sound
The vibrations are passed on through the ear, changed to electrical energy and transmitted to the brain
The brain then interprets and gives the sound meaning
How do we hear sound? Sound waves enter our ear and strike our ear drum (the tympanic membrane) and this vibrates our ear bones in the middle ear. These vibrations are transmitted to the fluid of the inner ear. In turn, this fluid vibrates the hair cells that line the inner ear. These hair cells are connected by neurons to the auditory nerve. The auditory nerve carries the signal to our brain where the sound is translated into information. The volume of the sound is determined by the number of hair cells stimulated and the pitch is determined by the distribution pattern of stimulated cells.

23. Can you guess what these sounds are?
Ask the students to recall the slide in the first lesson with the beluga whale and shrimp sound. Now play this slide and explain that how the brain interprets the sound and gives it meaning depends on our prior experience and what we know already. The interpretation of sound can be very subjective and what we hear and what we think we hear are not always the same for every person.
Frog
Humpback whale

24. Hearing Damage How much sound causes permanent damage? 140 1 minute
120
15 minutes
100 80
Below this level (70dB) – hearing damage negligible 60
Ask the students to recall that sound is produced by vibrations and because very loud sounds are high in energy they produce strong vibrations.
Now ask the students to predict what would happen in the ear if they were exposed to a really loud sound.
Explain that sound level is measured in decibels (dB).
Exposure to loud sounds can cause permanent damage to the nerves in the ear
Explain to the students that this slide shows in graphical form how exposure to very loud sounds can damage hearing over time.
Go through the slide with the students and note the sound level of discos and ask the students what they notice in their ears after they have been exposed to very loud sounds, particularly after a disco?
It is important to protect your ears in very loud environments e.g. discos > 120dB) 40 20 dB

25. Sound Level is measured in Decibels
Source of sound or noise
Sound level
(in decibels)
Jet taking off at distance of 30m
140
Threshold of pain
120
Disco loudspeaker 3m away
Pneumatic drill at road works 10m away
100
Busy street traffic 70
Ordinary conversation 60
Average whisper 20
Threshold of hearing
Explain that this is a table of the previous slide and note that the noise level in discos is at the threshold of pain.

26. Noise Protection Mandatory ear protection Ear muffs or ear plugs
Required in certain work environments where sound > 70dB
Explain that people working in loud environments e.g. construction sites are required by Health and Safety legislation to wear ear protection as their hearing would be damaged over time if they were exposed to sounds over 70 decibels.
Show the symbol for mandatory ear protection and the hard hat with ear muffs.

27. Assessment of student understanding
Combination of homework and a class quiz
Homework
An automatic focus camera is able to focus on objects by use of an ultrasonic sound wave. The camera sends out sound waves which reflect off distant objects and return to the camera. A sensor detects the time it takes for the waves to return and then determines the distance an object is from the camera. If a sound wave (speed = 340 m/s) returns to the camera seconds after leaving the camera, how far away is the object?

28. Class Quiz - Sound What is sound?
Give an example of sound energy being converted into another energy form?
How is sound produced?
What does sound need in order to be transmitted?
Why is there no sound in a vacuum?
What is an echo?
What is name used for the technique whereby some animals use sound for location?
What is the approximate speed of sound in air?
Ask the students the above questions to recap on this lesson and encourage them to provide every day examples to explain their answers.

29. Class Quiz – Sound (contd.)
The speed of sound in air can change with changes in __________ and ___________ ?
Through which of the following materials would sound travel faster (a) air, (b) water (c) iron
Why does sound travel faster in iron than in air?
During a storm a person hears the thunder before seeing the lightening, Why?
Why do people who work in noisy environments wear ear protection?

30. BIBLIOGRAPHY Websites

31. BIBLIOGRAPHY (contd.) Http://www.juniorscience.ie
Textbook – Exploring Science , 2003
O’Callaghan, M., Reilly, S. and Seery A., The Educational Company