Download What`s that buzzing noise? - School

What’s that buzzing noise?
Teachers’ notes
What’s it all about
Howard Stapleton has invented the Mosquito, a device that makes an annoying noise that
only teenagers can hear. The device emits a very high frequency tone and once over 25 we
lose the ability to hear this frequency range. In this activity children design a mobile phone
with a ringtone that only children can hear. They learn that humans have a different hearing
range to animals. In an extension activity they learn that pitch can be changed by varying the
length of a column of vibrating air. They use this knowledge to design a dog whistle.
Where it fits
Science:
QCA Unit 5F Changing sounds
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

that the term 'pitch' describes how high or low a sound is
how to change the pitch of sounds
that vibrations from sound sources need a medium e.g. air through which to travel
to the ear
Scientific enquiry


use data to make comparisons and to draw conclusions
use scientific knowledge and understanding to explain data or conclusions

Speaking and listening- putting together a case for a choice and discussing it with
a group
Literacy
Numeracy
 Data handling
What children will learn:

that the maximum pitch we can hear decreases as we age
Children will demonstrate this by completing the task on page 2 successfully.

that animals can hear sounds of a much higher pitch than adults
Children will demonstrate this by completing the task on page 3 successfully.

to use information about hearing ranges and pitch to decide what sounds human
and animals can hear
Children will demonstrate this by completing the task on page 4 successfully.

that a very short whistle will give a very high pitched sound and a long whistle will
give a lower pitched sound
Children will demonstrate this by completing the task on page 5 successfully.
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What you need to do
Introducing the activity

Display Page 1 of the activity through a data projector or on an OHT. Ask the
children if they have heard of the Mosquito device.
-Do different people hear different sounds? What about animals?
-What could be the purpose of such devices? e.g. dispersing crowds, deterring cats
from entering gardens etc.
-Would it be useful to have ringtones on your phone that only certain people could
hear? Why?
Leading the main activity

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Display Page 2 through a data projector or on an OHT.
Discuss how we hear. Emphasise the fact that sound travels as a vibration. Ask
the children whether they have noticed that their mobile phone vibrates when it
rings or receives a text message. If you want to explore the idea of pitch and
vibration in more detail before starting the activity then you may choose to do the
optional practical activity as set out below.
-
The graph illustrates how the maximum pitch we hear decreases as we
get older. Ask the children to use the graph to answer the questions.
More able children can be asked: Roughly what is the maximum pitch we
can hear aged 30 or 50?

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Display Page 3 of the activity through a data projector or on an OHT.
Ask children to work in pairs with a photocopy of the table. They need to
consider the maximum pitch the animal can hear. The animal will not be able to
hear any ringtone sound with a pitch greater than their maximum. In this example
the adult will only be able to hear the ‘Crazy frog’. The mouse on the other hand
will be able to hear any of the ringtones.

Display Page 4 through a data projector or on an OHT. Print off copies for the
children. Ask the children to use the table they completed on Page 3 to make
choices of ringtone for their mobile phone. They need to design and colour their
phone and cut it out. They will write the names of their pets, friends or relatives
and cut out and paste a ringtone for that caller.
Ask children to work in groups to compare designs and to identify three uses for
their variable ringtones e.g. to ring friends secretly or use their phone as a pet
whistle etc.

Optional extension activity
 Display Page 5 through a data projector or on an OHT. Print off copies for the
children. Find out what they already know about changing pitch. Use the example
of blowing across to bottles to show how varying the height of the column of air
affects the pitch of the sound.
Optional practical activity
This activity is called the straw trombone.
You will need:
* drinking straws
* a tall cup of water
What to do:
1. Put the straw into the cup of water.
2. Hold the cup in one hand and the straw in your other hand.
3. Holding the straw flat against the side of the cup, bring it up to your lips, just as if you
were going to drink.
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4. Now instead of putting the straw into your mouth, blow across the top of it. As you
blow, move the straw back and forth, up and down slightly. When you get the angle
just right, you will hear a whistling sound. This may be very faint, but with practice,
you can get a very loud, clear whistle.
5. Now as you are blowing, keep the straw still, but move the cup of water slowly
downwards. As the cup moves down, the tone of the whistle changes. Move the glass
upwards and the tone changes again.
What’s going on?
When you blow across the top of the straw, you cause the air inside the straw to vibrate. This
vibration causes the sound that you hear. By changing the length of the column of vibrating
air, you change the sound. The longer the column of air, the lower the pitch. The shorter the
column of air, the higher the pitch.
Why would moving the glass up and down change the length of the column of air? The water
inside the straw will move to the same level as the water outside the straw. As you move the
glass downwards, more of the straw is above the water level, so the length of straw that
contains air is longer. When you move the straw downwards, more water moves into the
straw and the length of the straw that is filled with air is shorter.


How does a dog’s sense of hearing differ to that of a human?
How can we create a high-pitched sound using a whistle?
The children should circle the phrases they think are correct. They can cut out
the dog whistle image. Ask them whether they think that the length of the whistle
needs to be changed. If so then they should alter the length as they see fit.
What would it look like if it were a dog whistle?
What would it look like if it were for humans?
Extension Ideas . . . Cross Curricular Links
Advertising a new mobile phone (Literacy):
Write a bulleted list describing the features of your new mobile phone design. How
can it be used? Why is it different from other phones?
Presenting information as a bar chart (Numeracy):
Convert the tables showing pitch, animal and ringtone into bar chart displays.
Discuss whether information is displayed more clearly as a table or a chart. Find
examples of when each is appropriate.
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Assessment for Learning: Smart Grid
Thumbs Up
We were
great at the
task
because…
Thumbs
Sideways
We were
good at the
task
because…
Thumbs
Down
We were OK
at the task
because…
We were able to
select appropriate
ringtones for all of
the animals
We identified callers
of different ages and
selected
appropriately pitched
ringtones
We designed a very
short whistle that
would give a pitch
audible to dogs
We were able to
select appropriate
ringtones for some
of the animals
We identified two
ringtones for two
different callers with
help
We were able to
select appropriate
ringtones for some
of the animals with
help
we . . .
Next time we will…
Smart Grids were devised by the Centre for Science Education
Science at your fingertips
What is pitch?
Sound travels in waves and pitch is the frequency of the wave. Frequency is the number of
times that the air is compressed and decompressed in a second, and is measured in cycles
per second, or Hertz (Hz). Low frequency produces a low pitched, bass sound. High
frequency produces a high pitched, whistle sound. Human ears respond to frequencies
between 20Hz and 20,000Hz. The human voice produces frequencies between 500Hz and
2,000Hz. Below 20Hz and above 20,000 Hz sound cannot be heard but it can still be harmful.
The ear is most sensitive to sounds between 1000 and 4000Hz.
What is the Mosquito device?
The device emits a high-frequency pulsing sound (around 17,000 Hz) that can be heard by
most people younger than 20 and almost no one older than 30. It has been used to deter
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teenagers from congregating around shops and public areas. The sound is designed to so
irritate young people that after several minutes, they cannot stand it and go away.
Why does our hearing deteriorate with age?
The cochlea is the spiral-shaped part of the inner ear. It contains 10,000 hair cells, which
move in response to sound waves, turning vibrations of the air into electrical signals and
sending messages to the brain. When high frequencies enter the ear, they only penetrate the
cochlea for a short distance, and are detected by sensor bundles near the entrance. Lower
frequencies travel much further along the membrane. As we age or our hearing is damaged, it
tends to be the high frequency sensors near the entrance that are affected first as they are
most delicate and are in a vulnerable location.
Why do dogs and some other animals have a better sense of hearing?
Dogs detect sounds as low as the 16 to 20Hz frequency range (compared to 20 to 70 Hz for
humans) and above 45 kHz (compared to 13 to 20 kHz for humans) and in addition have a
degree of ear mobility that helps them to rapidly pinpoint the exact location of a sound.
Eighteen or more muscles can tilt, rotate and raise or lower a dog's ear. Cats can hear up to
65 kHz. The shape and size of the ear plays a large part since it funnels the sound. An
example of this is the use of ear trumpets.
Web links
Compound Security
http://www.compoundsecurity.co.uk/deterrent_news_36.html
Describes products such as the Mosquito and other applications
Thinkquest Junior
http://library.thinkquest.org/3750/hear/hear.html
Your sense of hearing
Louisiana State University
http://www.lsu.edu/deafness/HearingRange.html
Frequency hearing ranges in dogs and other species
Ask a Scientist
http://www.newton.dep.anl.gov/askasci/eng99/eng99277.htm
How does a dog whistle work?
Ergonomics 4 Schools
http://www.ergonomics4schools.com/lzone/noise.htm
The Learning Zone – Noise
BBC Schools
http://www.bbc.co.uk/schools/scienceclips/ages/9_10/changing_sounds.shtml
Schools science clips - Science topics ages 9 – 10 Changing sounds
primaryupd8 is a joint initiative from ASE and the Centre for Science
Education, Sheffield Hallam University. We are grateful for support from the
Department for Education and Skills in developing this programme.
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