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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 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. 1 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 - 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? - 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. 2 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. 3 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 4 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. 5