• ## 01 Selecting and developing activitiesSl02TAnugget01 Suggestions

### Based on the Physics Narrative and the Teaching and Learning Issues

Ideas to emphasise here

• the physical aspect of the transmission of sound
• the source-medium-detector model
• the spreading of the vibrations
• the to and fro vibrations
• prepare the ground for frequency and amplitude being the fundamental characteristics
• vibrating objects, as sources and detectors
• reinforce the source-medium-detector model
• represent the vibrations of the source
• represent the vibrations in the medium
• represent The vibrations of the detector
• account for reductions in intensity with distance from the source
• link delays in hearing sounds to the trip time of propagation from the source
• show sounds travelling through solids and liquids, as well as gases

Teacher Tip: Work through the Physics Narrative to find these lines of thinking worked out and then look in the Teaching Approaches for some examples of activities.

Strategies for supporting learning

• put the source-medium-detector model to use
• connect vibrating objects to travelling vibrations
• connect hearing to the source-medium-detector model
• separate the to and fro movement of the particles that forms the vibration from the propagation of the vibration, which is also a movement
• showing large-scale, slow vibrations producing a sound
• emphasising that all sounds have a source
• tracing the chain from source to detector, via medium, often
• explore the range of hearing, along both the amplitude and frequency axes
• connect human hearing to what other species can hear
• ensure that the need for particles as a medium is always there
• link each sound heard back to the source, via the medium

Teacher Tip: These are all related to findings about children's ideas from research. The teaching activities will provide some suggestions. So will colleagues, near and far.

Avoid these

• using specious energy descriptions
• drawing or showing transverse waveforms
• asserting that sound is a wave without clarifying explanation of the idea of a wave – this is hard
• showing waveforms on an oscilloscope or computer
• introducing wavelength

Teacher Tip: These difficulties are distilled from: the research findings; the practice of well-connected teachers with expertise; issues intrinsic to representing the physics well.

• ## 02 A sequence to develop ideas about hearingSl02TAnugget02 Sequence

### Based on the Physics Narrative and the Teaching and Learning Issues

Hearing is a very significant sense to humans, and some sounds evoke strong emotional responses. The physicality of the sound is really important, both of making connections to the underpinning vibrations and for establishing a context for the learning and the emotional hooks. We therefore advise using physical sources, rather than recordings of sources, wherever possible.

Meeting reality: valuable experiences

• Noticing sounds from many different sources
• Hearing the wobble board in action
• Exploring collections of vibrating objects that make sounds of different loudnesses and pitches
• Semi-quantitative descriptions of the connection between different vibrating objects and the sounds that are heard
• Tracing out the paths of vibrations from source to detector

Teacher Tip: As many of these as possible should be direct physical experiences, rather than mediated through video or audio clips. This locates the learning in the lived-in world of the child, and grounds the learning in specific physical circumstances.

A sequence for developing the idea

This is a suggested sequence of activities, so a repertoire, on which to draw as you decide on a sequence to best suit the children in your own situation.

Noticing sounds

Brings children's attention the range and variety of sounds that can be heard in different places in their local environment. Executed so as to encourage beginning to think about and look for the sources of the sounds.

Sounds in the environment

An exploratory activity to begin to develop a descriptive language for sound (recognising the many qualities of the sound in addition to the more universal, but also more refined and abstract, quantitative measures).

Developing descriptions of sound

To begin to develop a shared description of sounds (drawn, spoken, enacted, maybe painted) in which you describe sounds. The interfaces for child-accessible apps for the creation of rhythm and melody might provide some stimulating starters. Such descriptions can be drawn on to begin to look for the sources of those sounds. Here electronic media don't provide such a rich suite of readily available metaphors and experiences. Richer physical experiences are more likely to support fruitful reasoning about the physical basis on which we hear.

What's in the box?

This is a useful extension or reinforcement activity, that can draw on, and develop the shared descriptions.

Making a variety of sounds

This activity reinforces physical vibrations as the basis of sounds: so the need to set an object vibrating to make a sound, and the varying ways in which it can vibrate, and perhaps also some ways in which it can be set vibrating.

Research work

It's highly likely that a number of topics rely on hearing as an essential component: for example many stories revolve around what can be year, and what cannot. Drawing these, and any current news into accessible reasoning and reporting takes some doing, but the strengthening of the network of ideas can repay this input. This may be experiential, document- based, or draw on existing topic work. It may be for the whole class, or only for some individuals within it. The focus should be on describing and reasoning about sounds and hearing.

Introducing sources

In this activity you can focus in on the idea that anything producing a sound must be vibrating. It starts off with sources that involve obvious vibrations and moves to sources with more subtle movements later.

Sound travels

Here you concentrate on the physical medium: connecting the source and the detector.

Talking telephones

Sending messages using sound enables you to think about transmitting the vibrations and preserving the patterns of those vibrations.

A noisy alarm clock

This activity focusses on the route which the vibrations must follow from source to detector in order for a sound to be heard, and ways in which you can vary the route to alter that sound.

Ear defenders

A design and suggest activity for varying the medium to affect the loudness of what is heard.

Range of hearing

This can reinforce the relationship between pitch and frequency by measuring the range of hearing using computer generated sounds.

Our detector – the ear

Here you can visit vibrations as the design of devices to detect sounds, including an outline structure of the ear, but also a functional description of microphones.

Measuring distance with sound

The speed of sound is used to measure distances – with a stopwatch. This has important links to many kinds of imaging, including ultrasound scans.

Tracking loudness

Here you use graphical plots, perhaps generated by a data logger, to tell stories about soundscapes with data.

Messages from research and practice: specific tripwires for this idea

There are several challenges to be met in teaching the sound topic, many of which revolve around the idea of vibrations that travel. We hear sounds, but you cannot point to the sound. The QuoteThis(sound) is really a name for a whole process.

As we begin to characterise sound , so separating out the loud and the quiet from the high pitch and the low pitch is facilitated by considered choice of descriptions and depictions.

Sounds and vibrating sources

All sounds are generated by the vibration of a source.

Sounds – groups of particles moving to-and-fro

Hearing a sound necessarily involves the to-and-fro movement of a physical medium.

Sounds travelling…not just filling

Sound can only fill a space to the extent that it travels through that space.

What travels and what doesn't travel?

Some children have the idea that sound is an entity that itself travels from speaker to ear. This view needs to be countered with the scientific view that sound is the name of a process, and not the name of an object.

Sounds getting softer

Typically children are quite happy to say that sounds get quieter as they travel further away from the source and suggest they die away. You'll need to encourage a more precise idea than this.

Separating loud/quiet (loudness) from high/low (pitch)

There are two separate simple ways of describing sounds, and you will need to help children differentiate between them.

Teacher Tip: These are reminders of, and links to, the Teaching and Learning Issues strand.

Representing and reasoning: doing physics

The source-medium-detector model, and the idea that vibrations travel from source to detector underpins a fruitful model of reasoning about sound. Sound is a useful label for the whole process of the vibrations making this journey and being detected by us. The vibrations have to travel in something and so a physical medium is needed: this can be solid, liquid or a gas. As the vibrations travel away from the source, so they spread and the sounds we hear become quieter.

• source-medium-detector model established and used.
• I hear a sound associated with the process of vibrations travelling from source to detector via a medium.
• travelling vibrations accounting for reductions in loudness as you travel away from the source.

Teacher Tip: Find out more from the Physics Narrative.

• ## 03 Noticing soundsSl02TAnugget03 Activity

### Listening to interesting sounds and beginning to describe them

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

To bring to children's attention the range and variety of sounds that can be heard in different places in their local environment.

Also, to begin to think about and look for the sources of the sounds.

What to prepare

• identified and sampled locations, around the school
• A recording frame

What happens during this activity

Choose three different sites around the school for the children to visit. Spend two or three minutes listening carefully to the different sounds at that site. Discuss what you notice about the sounds and make a record, either as a whole group or in small groups.

Here are some useful questions to help direct thinking:

Teacher: What sounds can you hear?

Teacher: Do you think what you're hearing is close to you or far away?

Teacher: Can you give a reason why you think what you're hearing is close to you or far away from you, even if you close your eyes?

Teacher: Can you see what is making the noises?

Teacher: How do you think the sound would change if you heard it indoors, say in the classroom?

Teacher Tip: This activity can be repeated beyond the school grounds, on other visits or on a specific local walk, or regularly on welly walks.

• ## 04 Sounds in the environmentSl02TAnugget04 Activity

### Comparing natural and man-made sounds

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

This activity is useful to begin to develop a descriptive language for sound (recognising the many qualities of the sound in addition to the more common quantitative measures). We think it's good to recognise the richness of the sense of hearing, rather than focusing in too rapidly on loudness and pitch as being the most easily quantified descriptions of the sounds.

So this is an exploratory activity, and is therefore somewhat divergent.

What to prepare

• scouted locations where a range of natural and man made sounds can be heard

What happens during this activity

This approach can be used at any time in the children's exploration of sound. It can be used as a starting point or to extend their understanding.

The children categorise the different sounds that they hear. You'll want to choose the categories with the abilities and interests of you class in mind. There are no rigid categories that are invariably useful at this early and exploratory stage.

You'll want to explore a variety of different ways of noticing and noting the differences and similarities. Discussion here supports both reasoning and a variety of representations is likely to prove fruitful if encouraged.

Here are some questions that we found useful to direct thinking:

Teacher: What would the world sound like without humans on the planet?

Teacher: What would the world sound like if there were no machines?

Teacher: What would the world sound like without birdsong?

Teacher: How can you explain to a friend that one sound is from a bird or animal, whilst another is artificial?

Teacher: Can you block out human noises?

Teacher: What's so special about hearing a human speak?

Teacher: Is this music? How would we decide if something is not music?

Teacher Tip: This can be used specifically in a science session or could lead to a cross-curricular imaginative writing activity in which the ideas of sound as travelling vibrations can be explored.

• ## 05 Developing descriptions of soundSl02TAnugget05 Activity

### Beginning to agree on some easily recognisable qualities

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

To begin to develop a shared way of describing sounds and the sources of those sounds. These representations can usefully blend words, drawings and computation as expressive media.

What to prepare

• a selection of three or four different items with which to make sounds

What happens during this activity

Take the objects one at a time, and elicit suggestions as to how to both make, and then vary, sounds.

Develop the discussion to explore various what if changes that could be made, as a way of exploiting the situation to develop the richness of the descriptions.

The object making the sound earns its place as the focus here, as this usually leads to good discussions, offering opportunities to develop vocabulary and other ways of representing the sounds.

• ## 06 What is in the box?Sl02TAnugget06 Activity

### Developing the vocabulary used to describe sound in a new and challenging context

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

Children will have started to describe sounds and come to some common agreement which allows them to communicate with each other. They will also have begun to think about the sources of those sounds, both what is vibrating and the quality of sound those vibrating objects give rise to. This is a chance to challenge and extend this evolving descriptive framework.

So this is a useful extension or reinforcement activity.

What to prepare

• a mystery sound box: a set of sealed boxes containing a variety of objects that act as sources

Small boxes are best as these can be handled by the children: an exercise in non-destructive testing. For each it will be essential for children to be easily able to find out how to create the intended noise (unless you are happy to engage with a very divergent activity). We'd suggest preferring boxes containing sources with rather physical sources (cow bells, dry rice in a pot, small stones) rather than electronic buzzers or anything which requires a loudspeaker.

What happens during this activity

Introduce the mystery sound box (or at least put up a screen to hide the source). Children hear sound and describe it. They try to work out what it could be or could not be, drawing on the work in describing sounds which they have already done.

Encourage the children to make explicit connections to sounds that they have heard and recorded before.

Teacher: What does it sounds most like?

Teacher: Where and when you would you normally hear such a sound?

This is an excellent activity for a 5 minutes class mat time or small group work. Both these can be run either by an adult or by a child. The evolving ideas and the reasoning rather than the final decision, are the target. Although it is a good idea to have a good means of revealing the source to avoid frustration. Even when the reveal takes place, it's not to award right and wrong badges.

Better to ask:

Teacher: Are there any tests you could have done to decide between the different opinions about what you thought it was?

• ## 07 Making a variety of soundsSl02TAnugget07 Activity

### Different ways to make sounds

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

This activity reinforces the need to set an object vibrating to make a sound, and explored the varying ways in which it can be set vibrating.

What to prepare

• pencil and paper
• perhaps display cards
• a small collection of objects (Perhaps a few rounded stones, a few short lengths of string, a rubber band, a piece of paper, a 15 cm ruler

What happens during this activity

Set the children a class group or individual task of listing how many different ways they can find to make noise using the object, or the small set of objects.

Do spend some time to get the children thinking along the right lines by activating the previous work in this area. Similarly do conclude with a plenary discussion to highlight some key findings, amongst which might be:

• something must vibrate
• the vibrations can be big or small
• the vibrations can be rapid or slow

To reflect on, analyse or record their findings the children can:

• present a report, either written or oral
• group the sounds they hear into categories using display cards by moving to stand by these cards
• ## 08 Research workSl02TAnugget08 Activity

### Some finding out to reinforce the ideas met so far

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

Further exploration such as for individual topic work or homework / home learning can help to extend the childrens' experiences and understanding.

What to prepare

• a curated set of appropriate research sources

What happens during this activity

Set a number of research tasks, each matched to the abilities and crucially, the particular interests of the children. Do bear in mind the research facilities that are likely to be available in the home, or other locations in out-of-school hours.

Here are a sample:

• Choose an animal and then find out how it makes sounds, and why it makes those sounds.
• What are the 5 most peculiar sounds you have heard? Why did you think of them as peculiar?
• What are the 5 most odd sounds that you can think of? Why are they odd?
• List 5 sounds you never expect to hear. Why do you never expect to hear them?
• ## 09 Introducing sourcesSl02TAnugget09 Activity

### Activity preparations

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

This activity focuses on the idea that anything producing a sound must be vibrating. We think it best to start off with sources that involve obvious vibrations and then look at more subtle movements later.

What to prepare

You will need a collection of things that vibrate along with the means of showing that they do vibrate. We suggest:

• a large panel of hardboard (approx: 1 metre by 1 metre) popularised as the wobble board
• a tuning fork and a bowl of water, together with a table tennis ball suspended on a long piece of fishing line
• a large open loudspeaker, a means of playing music and some dried peas

To take it further:

• a small wind-up music box and access to a table to use as a sounding board
• a small loudspeaker (50 millimetre diameter) and access to a pane of glass

Safety note: Signal generators driving loudspeakers have been known to produce unpleasant feelings, even nausea, in susceptible individuals at a variety of frequencies from as low as QuantityWordspread{4}{15}{hertz}to above 20 kilohertz.

### Making sources

What happens during this activity

Start with the wobble board – just wobble it to and fro slowly in an exaggerated action. As you increase the rate of wobbling, start to talk about the vibrations of the board, connecting this use of vibration with the to and fro action. Ask what the board is doing to the air next to it. Slow the action right down so you can emphasise the push and pull on the air. Emphasise that the vibrating board sets air into a to and fro motion.

Introduce the tuning fork as something which makes a sound, but which we cannot see moving. (In fact our eyes cannot react fast enough to catch it moving, added to which it is not moving very far.) You can show that the prongs of the tuning fork are moving by dipping the end in a bowl of water. Try drawing the children in close as you demonstrate this on the pretext of trying to see the very small vibrations. The children will be wetted by the water particles as they are displaced by the to and fro action of the fork.

### Extensions and discussion

An alternative is to suspend a table tennis ball on a long piece of fishing line beside the vibrating fork, so that the fork collides with it at the extremity of its vibration.

A further way of seeing the vibrations is to polish up one end of the tuning fork (right at the end) and then bounce a light beam off the outside of the end at a glancing angle , so that the reflected spot ends up on the wall a long way off. This is tricky and time-consuming to set up.

To make lots of air vibrate (as you did with the wobble board), just place the stem of the tuning fork on a wooden table and listen out as the table is set vibrating. A nice alternative is to have a music box playing, first with it held in the air and then with it resting on the table.

A further activity at this stage involves setting up a circus of vibrating objects (including a range of musical instruments) and getting children to spot the vibration that is acting as the source of the sound.

To use the loudspeaker, place the loudspeaker so that it faces upwards and then put the dried peas on the surface. With the loudspeaker connected to the music system, the peas jump about as the speaker cone vibrates.

Two extensions to discuss:

• Rooms can be bugged by bouncing light beams from the windows (health and safety is not so much of a concern for spies, but we don't suggest you try this), detecting any to and fro motion of the window pane. What would create such a motion? This is the stuff of spy stories.
• Small loudspeakers are available that can be clamped to window panes. The loudspeaker sets the whole window pane vibrating to get lots of air moving. This produces a much louder sound.
• ## 10 Sound travelsSl02TAnugget10 Activity

### Routes taken by vibrations

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

This puts the focus firmly on the medium that connects the source and the detector. The physicality of the medium is important, and it will be a good idea to name the solid, liquid or gas through which the vibrations are travelling.

What to prepare

• a model ear or a good clear diagram
• a microphone, linked to a computer running sound-analysing software)

What happens during this activity

Choosing context, either a physical one to hand, or a good clear image or diagram. Children should discuss the route that the travelling vibrations follow in their journey from source to detector.

Structuring the activity will depend on the confidence of the children and on the difficulty of the example chosen. You may need to use some prompting questions, such as these:

Teacher: Where do the vibrations start their journey?

Teacher: When we hear the sound, where do the vibrations end their journey?

Teacher: What do the vibrations travel travel through on their route between the source and the detector?

We've found the following focii to be useful:

• A focus on routes, and what can and cannot be heard
• - ListItem{Emphasising the link between quieter with distance from source and the spreading of the} vibrations.
• Using very different environments and noises, such as whale song
• ## 11 Talking telephonesSl02TAnugget11 Activity

### Vibrations travel from source to detector, along with string

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

Sending messages using sound enables us to think about the vibrations. This activity, as well as enabling an engaging and exciting sound related experience, can be used to explore factors that affect how well the vibrations make their journey. You might also use the situation to allow children to suggest and make systematic variations. In some cases it will be appropriate that children can explain to supporters and carers some aspects of their work using similar apparatus at home.

What to prepare

• a string telephone
• several different pots for the ear and mouth pieces
• several different lengths and thicknesses of string

What happens during this activity

The children can set up the apparatus and explore how it works by sending messages. Encourage descriptions and depictions that focus on the route followed by the vibrations.

We've found it helpful to provide a starter diagram to encourage labelled drawings to explain their findings and reasoning.

Then they can be set the task of suggesting changes and trying them out – perhaps led by more questions that become more specific to focus the thinking.

Teacher: What affects the sound you hear?

 

Teacher: If I change this one thing then what happens to the sound that you hear?

This can open all kinds of interesting discussions, and you'll need to have a strategy to draw it to a close.

Perhaps you might risk some topicality by asking:

Teacher: Can you listen in to the messages whilst they are en route, so bugging the telephone?

• ## 12 A noisy alarm clockSl02TAnugget12 Activity

### Help with fixing noisy and quiet devices

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

Children think about the path which the vibrations must follow from source to detector in order for this sound to be heard. To make this goal orientated, and to allow for little lateral thinking, we suggest sketching two scenarios in which the path is able to transmit more of vibrations from the source and in which the path is able to translate less of the vibrations from the source.

What to prepare

• A noisy, mechanical alarm clock: the more obvious and bell-like the ringer, the better

What happens during this activity

Set up a situation as a puzzle to be worked on in one of these two possible ways:



Teacher: My granny bought me an alarm clock. It's great and I like it very much – it wakes the whole house up as well as me and my teddy. How can I make it quieter without upsetting my granny by damaging the alarm clock?

Or:

Teacher: I bought my teddy an alarm clock, but my teddy sleeps very heavily and he doesn't wake up properly. How can we make the alarm clock louder to help him?

It is perhaps best to set this up as an open-ended activity, Giving pointers or hints as necessary. It's very likely that you'd managed to think of other examples of every day activities which can be substituted for these two.

• ## 13 Ear defendersSl02TAnugget13 Activity

### Designing devices to defend your ears

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

Children think about the path which the vibrations must follow from source to detector in order for this sounds to be heard, and how to reduce the loudness of those sounds.

To make this goal orientated, and to allow for little lateral thinking, we suggest using a situation in which you wish to reduce the loudness of the sound heard.

What to prepare

• images of noisy workplace locations
• images of people wearing ear defenders of various designs

What happens during this activity

Select a context when children would expect workers to hear loud noises (heavy vehicle drivers,  quarry workers, farmers, tanks, firework display workers, factory workers, armoured vehicle drivers).

The selection could profitably link with any one of a wide variety of topics that the children will be studying in the curriculum and so with many cross-curricular links.

Set the task of finding the most successful way of reducing the noise level reaching the workers ears.

Allowing a very wide exploration initially encourages children to explore all sorts of methods and helps them develop a deeper understanding of the physics that is taking place. You might set the class a group challenge of sketching out as many different solutions as they can in 10 minutes.

Although these activities might be seen as a design exercise, and so be primarily a Design and Technology activity, it's important that the story of the route taken by the travelling vibrations is central.

Two approaches that encourage this:

Teacher: You have the design idea – that's good. Now, what materials are you going to use and why? Can you prove that your suggestion is most successful?

Teacher: Imagine you are the science testing department of a company that is designing ear defenders for…We have been asked to find out which material will be the most suitable to use in the…part of the design.

Discussions may well follow about the purpose of the material and about sound insulation.

You can extend this by devising and testing the proposed materials to find the one most suited to the tasks.

Further teaching ideas that embed the physics still further such as presenting the idea to the Board of Directors of a fictional company as a recommendation. You might split the class into Science Design Teams and suggest that the contract will go to the best team.

Emphasising that the company will be investing £XXX into the recommendation will provide additional motivating context.

Children will very likely recognise that multiple factors are involved, such as being heavy or waterproof, then they can either include these in their recommendations or be encouraged to focus only on the extent to which they reduce the vibrations reaching the ear.

• ## 14 Range of hearingSl02TAnugget14 Activity

### The audible range

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

The aim of this activity is to reinforce the relationship between pitch and frequency, and to give some feeling for the numbers involved when measuring frequencies. Measuring something about themselves also allows children to make real connections to the topic.

What to prepare

• A computer running software that allows you generate and play back different frequencies. In all cases pure notes of a single frequency are best.)
• Download file

What happens during this activity

Play back a note of audible frequency and loudness. Ask the class to put their hand up if they hear the note. Now move progressively to higher and higher frequencies. Instruct the children to keep their hands raised until they can no longer hear the sound. In this way it is possible to identify the upper threshold of frequency response of the ear and the variation in this figure between members of the class. Repeat the procedure for the lower frequency threshold, moving down through the frequency scale.

At the upper end of the spectrum you might want to turn down the loudness control so that there is actually no sound! This little trick will weed out those children who are a little too enthusiastic in their claims. You might even want to discuss using this approach to make the findings of the demonstration more reliable. It has parallels with placebo testing in medicine.

• ## 15 Our detector – the earSl02TAnugget15 Activity

### Investigating detectors and describing the process of detection

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

This activity focuses on the design of devices to detect sounds. The structure of the ear is important here, but you will also want to be able to refer to microphones, as these transform the vibrations of the air into electrical vibrations.

What to prepare

• a model ear or a good clear diagram
• a microphone, linked a computer running sound-analysing software)
• a carefully chosen, large microphone opened up to show the parts

What happens during this activity

Lead the class through a discussion whilst looking at the model ear, or at any sound sensing system, to draw out the way in which the to-and-fro motion of the medium is picked up by the detector. You should also point out that the brain works through processing electrical signals, and that's why ears have to perform this transforming action (from vibrations of the air to changing electrical signals in the brain). Microphones perform exactly the same transformation.

Connecting a microphone to a computer running suitable software can give a large-scale, clear representation of the vibration as a vertical trace on the screen. We strongly recommend that you do not produce a time trace, as explaining the resulting wave-like pattern is likely to lead children's thinking down the wrong tracks. It is better to keep things simple and to make the link: from the vibration of the sound to the vibration of the microphone diaphragm to the up and down vibration of the spot on the screen (producing the vertical line).

• ## 16 Measuring distance with soundSl02TAnugget16 Activity

### Timing echoes

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

A widespread activity in secondary schools is to make a rough measurement of the speed of sound by timing the gap between making a sound and hearing an echo from a wall at a measured distance.

This activity takes things the other way around by assuming the speed of sound (340 metre / second), measuring the time the sound takes and using this information to find the distance that the sound travelled.

What to prepare

• a sonic ruler (These are available from many hardware stores. When working it should emit an audible click and then report the distance to the object you pointed it at.)
• an outside wall, about 150 metre away from where the children can stand
• a stopwatch, accurate to 0.01 second

What happens during this activity

Start with the sonic ruler and ask if anybody knows how it works. Point out that it seems to be able to measure how far away an object is, simply by bouncing a sound off it. Ask how this is possible. The ruler actually measures the time that a sound pulse takes to travel to and from the object, then finds the distance by multiplying half the round-trip time (out and back) by the speed that it has it has stored in its memory.

This speed will be 340 metres in each second, so the distance will just be the number of seconds multiplied by this speed.

The next activity takes the class outside. The challenge is for the children to find their distance from the wall using the known speed of sound (340 metre / second) and half the round trip time that they measure. Different groups of children will need varying amounts of help in carrying out this activity:

• Stand about 150 metre in front of the wall.
• Make a loud sound (maybe clapping two blocks of wood together).
• Time how long it takes to hear the echo from the wall.
• Calculate the distance.

It's good fun to run this activity as a competition. It is also a good place to think about the possible uncertainties in this experiment – beware of those who get suspiciously close to the correct result. How reliable are they as witnesses? This can lead to lively discussion.

This activity offers the opportunity to make connections to the technique of remote sensing. For example, ultrasonic imaging of pre-natal lambs (and Human babies) are done in exactly the same way. Times are measured for ultrasound pulses to travel to and from the foetus, then distances of the surface from the probe are calculated.

It would be good to have a number of impressive images, developed by remote sensing, to hand.

Teacher: These images are all made by timing.

• ## 17 Tracking loudnessSl02TAnugget17 Activity

### A story told with decibels

This a part of a suggested sequence:

A repertoire to develop the idea of hearing

What the activity is for

This emphasises the graph as a story about something and a way of communicating. It is an opportunity to increase children's familiarity with the decibel scale.

What to prepare

• portable dataloggers with sound sensors (You'll ideally need a number of portable dataloggers with the ability to see what you have captured, fitted with microphones and rigged to measure loudness in decibels. Failing this you can record the sound using any device, then feed it into such a datalogger later. However, this will only reliably give relative values, thus undermining a part of the purpose of the exercise.)

What happens during this activity

1. Challenge the class to find an event where the sound level varies in an interesting way.
2. They should record the sound from this event, then tell the story of one aspect of the soundscape using a graph.
3. They should be allowed full access to graphical analysis and annotation tools, so that the computer does more than plot the graph. The final product should tell an interesting story.
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