Experiments

Sound: From musical boxes to iPods

Powerpoint Slide 1 should be showing as the class enters. (Some cheerful music could be playing - if this is convenient - switch it off before starting.)

1. Demonstration

Aims/Facts

  • To catch the children’s attention and find out what they know.
ActivityDiscussion
Hold up the drive mechanism of a musical box which is playing.

Then touch the mechanism on a metal tray or metal tray.

View Apparatus List
As you hold up the mechanism, ask what the children can hear. Only a few close to the front will hear anything.

Once the mechanism is held against the tray the tune should then be heard loudly. Ask them to try to explain.

 


2. Discussion

Aims/Facts

  • Sound travels from a source to their ears.
ActivityDiscussion
 Ask how they hear the sound.

Discuss the sound being produced and then travelling to their ears.

 


3. (Show Powerpoint Slides 2,3,4)

Aims/Facts

  • There is no air outside the space craft so the astronaut’s calls would not be heard by those inside the space craft.
  • Sound needs something to travel through (e.g. air).
ActivityDiscussion
Explain that sometimes astronauts have to climb outside their spacecraft to make repairs. Point out that the earth can be seen so far away that the curvature of the horizon is clear.

In Powerpoint Slide 3 the space ship is reflected in the astronaut’s visor.
Point out that if someone shouts outside a house, the sound can be heard inside the house. Space ships have very thin outer skins. Ask whether, during a space walk, an astronaut could be heard by those inside the space craft. If they are not sure, point out that some of the pictures show the astronaut attached to a line. Ask what it is for. (For Communications and to prevent the astronaut moving away from the space ship and being lost.)

 


4. Demonstration (Show Powerpoint Slide 5)

Aims/Facts

  • Conclude that air does not travel with the sound.
ActivityDiscussion
Use an Airzooker to send a waft of air across the classroom to blow the hair of some of the children.

View Apparatus List

Safety Note: The Airzooker can send a blast of air which surprises a child near to the speaker. Use it first to send a blast of air to those furtherest away from you.
Point out that there is air in the classroom and they can hear you speaking. Then ask the children whether they feel a rush of air when you speak.

They will enjoy this and understand that sound does not travel with the air.

Explain that there must be another explanation.

 


5. Class activity: ‘dance’

Aims/Facts

  • As the sound travels, the individual particles vibrate and do NOT travel with the sound.
  • This is called a sound wave.
ActivityDiscussion
Ask about 10 volunteers to line up across the classroom all facing towards one end of the line. Child 1 should start to step. The as soon as child 2 sees child 1 move, 2 should start to step. As soon as child 3 sees child 2 move, 3 should start to step.

A second group could dance, if there is time. Show Powerpoint Slide 6.

View Apparatus List

Safety Note: During the dance, children should be warned to take small steps so they do not tread on each other’s feet. Good behaviour is essential. Any child who is uncooperative should be sent from the line.
The remainder of the class should watch and explain what they see.

The line should automatically form bunches which move along the line to represent the sound travelling. Point out that the children do not move along the line. Only the bunches move along: the individuals just vibrate.

Ask them how the dance could represent quiet sounds and loud sounds.

 


6. Discussion (Show Powerpoint Slide 7)

Aims/Facts

  • A sound wave travels from the source to our ears.
ActivityDiscussion
 When the alarm rings we do not feel a rush of air. The sound wave travels from the alarm to our ears.

 


7. Demonstration

Aims/Facts

  • Vibrating objects produce sound.
ActivityDiscussion
Singing rod

Hold the rod lightly with two or three fingers at its mid point and then with the other hand rub the rod slowly from the centre outwards in slow sweeping movements. The rod will vibrate and sound a note. The vibrations are longitudinal. If the end of the rod is pointed towards the class they will hear a louder sound.

View Apparatus List

Ask the class to hum gently and to feel their throats at the same time.

Safety Note: Singing rod: this can produce a loud sound. If the children appear uncomfortable then do not excite the rod further. Rosin, particularly when powdered, is a sensitizer which can give rise to allergic dermatitis. It is safest to put the rosin in a cloth and then rub the rod with the part of the cloth carrying the rosin. The children should NOT touch the rod which has been rubbed but the end should be safe enough.
Invite the children to touch the end of the rod and feel the vibration. This is not felt along the rod only at the end showing the rod is vibrating longitudinally.

(A rod made of a different material or of a different length will produce a sound of a different frequency and can be used in later activities if available.)

Ask what they feel and explain that these are vibrations. They may have done this in at KS 1, but it is a quick way for them to learn what vibrations are.

 


8. Quiet sounds

Aims/Facts

  • Reinforce that sounds are made when things move.
  • To make quiet sounds small movements are needed.
ActivityDiscussion
Ask them to be very quiet and try to make no sound at all. They quickly find that they need to be very still. Sounds outside the room such as traffic seem loud.After a moment someone will move and make a chair squeak or drop something, which will sound loud. When they are very still, ask them to start to make very quiet sounds – they must not speak!

They find they need to move and perhaps tap something.

 


9. Loud sounds

Aims/Facts

  • Loud sounds are made by large movements
ActivityDiscussion
If you think they will behave well you could make a pact that they will go quiet when you raise your hand. Then ask them to make loud sounds- without speaking.They will find that loud sounds are associated with large movements.

During discussion link this with vibrations.

 


10. Discussion about listening (Show Powerpoint Slide 8)

Aims/Facts

  • Some animals can hear very quiet sounds
ActivityDiscussion
Ask them to describe the kitten’s ears.

They are large and point forward. The cat is able to detect very quiet sounds because the large ears collect sound waves over a wide area. The ears point forward so the kitten turns its head or its ears to hear where the sound comes from.
 

 


11. Activity

Aims/Facts

  • Human hearing is very sensitive to direction.
ActivityDiscussion
The ends of the sound tubes should be placed over the ears of a volunteer. Then the tube tapped and the volunteer asked which side the sound comes from.

View Apparatus List

Safety Note: Sound tubes: once joined these are long and should not be whirled around near the children.
Human ears are on the sides of the head with small ear flaps that point slightly forward. The ears detect the sound and send messages to the brain.

The two ears send different signals so we know from which direction the sound is coming.

 


12. Extra (Show Powerpoint Slide 9)

Aims/Facts

  • Soft materials absorb sound.
ActivityDiscussion
Absorption of sound

(Note the kitten is much younger in this picture than in slide 9)
Ask why the kitten is looking unhappy?

They will suggest that it does not like the hat. Then ask if they think it will still be able to hear.

This can lead into a discussion about soft materials absorbing sound which would link well with investigation work that the teacher may be planning.

Point out that because the hat is thin it will not absorb all of the sound.

 


13. Discussion (Show Powerpoint Slide 10)

Aims/Facts

  • Sound will travel through water.
ActivityDiscussion
The whales communicate with a sort of song. They make the sound underwater and it travels long distances through the water.

(Beluga whales are very social and make a wide variety of sounds.)
Ask them whether they can swim underwater. Ask whether they can hear if the side of the swimming bath is thumped when they are underwater.

They may point out that they do not hear voices above the water well. Explain this is because the sound does not pass through a change of material well. This will be useful when explaining ultrasound.

 


14. Activity

ActivityDiscussion
Tunes from a coat hanger

View Apparatus List

Use a coat hanger with a piece of string tied at each corner as shown in the apparatus list.

Show the Marvin cartoon on slide 11 after the volunteer has reported what was heard.

Safety Note: Tunes from a coat hanger: warn children of the danger of putting objects in the ear.
Ask for a volunteer. Wrap the ends of the string round a finger of each of the child’s hands. Then say ‘Now put your fingers in your ears’. Tap the coat hanger gently with a metal object. Ask whether the sound was loud. Tap again without the fingers in the volunteers ears. Discuss the difference in the loudness.

Explain that the sound travels through the metal and string more easily than through the air.

 


15. Extra - Bush Telephone (Show Powerpoint Slide 12)

Aims/Facts

  • Sound will travel through string and other materials.
  • Sound does not only travel through air.
ActivityDiscussion
View Apparatus List

Ask a child to take one cup as far as the string will allow across the classroom. Child 2, who should be close to the front of the class, should hold the second cup again an ear. Arrange that the string is held taut. Blindfold child 2 with a soft dark scarf. Then hold up a card showing a simple message. Ask child 1 to whisper the message into the cup and then ask child 2 what is heard.

This activity can be expanded by having a few cups linked together by taut string and then the message should reach children 2, 3 etc.
Child 2 should hear the message clearly.

If a child takes hold of the string the listener will not be able to hear. Also if the string is slack nothing is heard.

Make sure that the children understand that the sound travels through the string. They might notice that the message can be heard very quietly close to the string – but not nearly as well as via one of the cups.

 


16. Extra

ActivityDiscussion
Telephones (Show Powerpoint Slides 13,14)

A very simple diagrammatic explanation of a telephone is provided. Explain that the sound is changed into an electrical signal by a microphone in a sound system – the information travels as an electrical signal through amplifiers etc to a loudspeaker. A loudspeaker or earpiece changes the electrical signal back into a sound message. A telephone works in a similar manner.
This has been included in response to questions from children during the trials.

The idea that the message can travel as an electrical signal can be linked back to human hearing. Point out that when sound reaches our ears then message is sent to our brain as an electrical signal.

 


17. Extra (Show Powerpoint Slide 15)

ActivityDiscussion
Mobile phones

There is an extra stage in the communication with the sound changing to first an electrical signal then to a radio signal.
The children ask lots of questions and this is an opportunity to link the science with their everyday experiences.

 


18. Discussion (Show Powerpoint Slides 16, 17, 18)

Aims/Facts

  • Large objects usually produce low pitch sounds. Small objects usually produce high pitch sounds.
ActivityDiscussion
Link low notes and low pitch and also link high notes and high pitch.

(The children who play instruments may know the word pitch)

Ring a small bell when you show slide 19 and ask whether the large bell would make the same sound.
Ask what noise a cow makes. They will enjoy making moooo sounds. Then ask what sound a baby mouse makes. They will squeak.

They will know that the cricket makes sounds by rubbing their legs (knees) together to produce an even high pitch sound.

Bring out – large objects make low notes and small objects make high notes.

The large bell is in Siena, Italy. Ask what sound the large bell will make. Discuss the difference between the bells.

 


19. Straw Oboes (Show Powerpoint Slide 20)

Aims/Facts

  • Large things make low pitch sounds.
  • Small things make high pitch sounds.
ActivityDiscussion
Ask 2 children to give each child one straw. Prepare the straws as on the apparatus list. Explain that they should blow the cut end to make a sound. Ask them to put up their hands when they make a sound. It is often children who have not contributed much who make the sounds first. Encourage them to keep blowing and snip about 2 cm off the end of the straw. Repeat this so that the class hears the note increase in pitch.

View Apparatus List

Safety Note: for hygiene reasons the straws should not be passed from child to child.
This is a good activity to catch the interest of the children who have not answered questions so far. Once a child can make the sound, raise your hand for silence and ask the child to come forward, then snip the straw quickly about 1 cm at a time. Some groups may be able to cut the straws – but this approach ensures they all hear the increase in frequency.

Summarise the discussion using Powerpoint Slide 21.

 


20. Introduce the word frequency (Show Powerpoint Slide 22)

Aims/Facts

  • Low pitch = low frequency
  • High pitch = high frequency
ActivityDiscussion
 Powerpoint Slide 23 provides some extra examples for discussion.

 


21. Class Activity (Could be omitted)

Aims/Facts

  • Bottles with different amounts of air in them produce different sounds.
ActivityDiscussion
Give out plastic bottles part full of water to volunteers in each class group. Ensure that each group has similar bottles with different quantities of water in them.

View Apparatus List

Show the children that if you blow across the neck of the bottle a note is produced.

Safety Note: for hygiene reasons the bottles should not be passed from child to child.
Children find this quite difficult but fun. They notice that the more air in the bottle the lower the sound.

Lead into the next demonstration.

 


22. Manometer demonstration

Aims/Facts

  • The more air in the bottle, the lower the frequency.
  • The less air in the bottle, the higher the frequency.
ActivityDiscussion
Blow across the neck of the bottle attached to the tubing in order to make a note. Ask the teacher accompanying you to raise and lower the reservoir so that the amount of water in the bottle varies. The note produced can be varied to make a tuneful sound.

View Apparatus List

Safety Note: Manometer experiment: if the apparatus leaks slightly, it should not be demonstrated near electrical equipment.
Discuss what is changing as the note changes.

Point out that wind instruments are blown.

The discussion should provide an opportunity to ask which wind instruments the children are learning to play.

 


23. Wind instruments

Aims/Facts

  • The longer the air column, the lower the note.
ActivityDiscussion
A ‘Swanee whistle’ makes an intriguing sound

View Apparatus List

Children often play recorders.

The lowest note on a recorder is sounded when all the holes are covered. Show how when the air column is effectively shortened- the frequency rises. If available show a soprano recorder that has ?? as the lowest note and explain that the vibrating air column is small – hence the higher pitch note.
Use any wind instruments that are available to reinforce the ideas covered so far.

 


24. Stringed instruments (Show Powerpoint Slide 24)

Aims/Facts

  • The thicker the string the lower the frequency.
  • Shortening the length increases the frequency.
  • Link both to previous ideas.
ActivityDiscussion
Show a violin or other string instrument and point out that the strings are the same length but make different sounds.Ask the children to show their stringed instruments.

Ask what else they notice apart from the length. Some will spot that the strings are of different thicknesses. Link with size.

Those who play a stringed instrument will know that the note can be varied by changing the tension.

Point out this can be used for tuning.

 


25. Elastic box

Aims/Facts

  • The tighter the elastic the higher the frequency.
ActivityDiscussion
Stretch a length of fishing pole elastic and pluck it. The sound will be very quiet.

Clip one need of the fishing elastic to one edge of a metal box. Stretch the elastic across the box and pluck it. They should hear the sound clearly. This is a good opportunity to link back with the musical box movement.

View Apparatus List

Stretch the elastic round the box a few times increasing the tension each turn. Secure the elastic with a bulldog clip or round your finger and then pluck each turn separately. The tighter the elastic the higher the note.

Safety Note: Elastic box: this should be demonstrated. Fishing pole elastic is strong but care needs to be taken when it is stretched. If over-stretched, it may break and flick back painfully. If this is considered a significant risk, eye protection should be worn by the demonstrator and the children should not be too close. Similarly, care should be taken if the tension of strings on stringed instruments is changed.
Bring out from the discussion the need for a sound box for string instruments. Point out that electric guitars do not have a sound box but use electronic systems to amplify the sound.

(This could be extended into an investigation for another occasion. The children could stretch elastic bands across a food container and observe that changing the tension, thickness or length changes the frequency.)

 


26. Revise ideas so far (Powerpoint Slide 25)

 


27. Sound systems

Aims/Facts

  • Use to reinforce ideas.
ActivityDiscussion
Explain that sound systems have loudspeakers which vibrate and cause the air to vibrate.Headsets vibrate a small amount of air so have to be placed close to one person’s ears. Large loudspeakers cause large vibrations in large amounts of air so the sound travels to many people.

Link with Radio, CD players, iPods etc

 


28. Ultra sound (Show Powerpoint Slides 26, 27)

Aims/Facts

  • Ultrasound is used to see inside people and can see babies before they are born.
  • Explain that knowledge about sound has made it possible for scientists to develop ultrasound scans. Doctors use the scans when caring for people.
ActivityDiscussion
Ask if they can spot the baby.Ask who has a dog. Then whether they have dog whistle. Ask why it would have not been very useful if you had brought one. They will know that the dog whistle sounds a very high note that humans can hardly hear at all. Explain that if very, very high frequency sound is produced it can be used to ‘see’ inside people.

They will ask whether the picture is like an x-ray. Explain that the sound bounces back off surfaces so it bounces back off the baby to build up a picture.

 


29. Summary (Show Powerpoint Slide 28)

Aims/Facts

  • Physics is everywhere.
ActivityDiscussion
Go through the list of uses of sound and its applications.Explain that scientific knowledge about sound has made it possible for iPods etc to be developed.

Powerpoint Slide 29