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© Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 1 of 36 KS3 Physics 8L Sound and Hearing.

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Presentation on theme: "© Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 1 of 36 KS3 Physics 8L Sound and Hearing."— Presentation transcript:

1 © Boardworks Ltd of 20 © Boardworks Ltd of 36 KS3 Physics 8L Sound and Hearing

2 © Boardworks Ltd of 20 © Boardworks Ltd of 36 8L Sound and Hearing Contents What is sound? Speed of sound The ear and hearing Summary activities Reflecting sound

3 © Boardworks Ltd of 20 © Boardworks Ltd of 36 What causes sound? The tuning fork vibrates and you hear a sound. Sounds are made when an object vibrates. Take a tuning fork and strike it against a block of wood. What do you observe?

4 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Good vibrations! What vibrates so that the following make sounds? violin strings voice box loudspeaker cone drum skin

5 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Remove the air from the bell jar and what happens to the sound? The bell-jar experiment Place a ringing clock inside the bell jar and what happens? There is air inside the bell jar so the sound can travel and be heard. The sound cannot be heard because there is no air inside the bell jar (a vacuum). vacuum pump on

6 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Sound waves can be studied with this type of equipment. signal generator oscilloscope loudspeaker Studying sound waves A signal generator produces different types of signals. A loudspeaker converts signals from the signal generator into sound waves. An oscilloscope shows wave patterns and allows us to ‘see’ sound.

7 © Boardworks Ltd of 20 © Boardworks Ltd of 36 The larger the amplitude of the wave on the trace, the louder/quieter the sound. Loudness and amplitude A sound can be quiet or loud. loud soundquiet sound On an oscilloscope trace, the loudness of a sound is shown by the height of the wave. This is called the amplitude. Which word should be crossed out in this sentence?

8 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Which is the loudest? Sound A is the loudest. Which trace represents the loudest sound? Sound A has the largest amplitude (i.e. the tallest waves), so it is the loudest of these two sounds. AB

9 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Pitch and frequency A sound can be high or low – this is the pitch of the sound. low pitch soundhigh pitch sound On an oscilloscope trace, the pitch of a sound is shown by how many waves there are. This is called the frequency. Which word should be crossed out in this sentence? The greater the number of waves across the oscilloscope trace, the lower/higher the frequency and pitch.

10 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Which is the highest? Which trace represents the sound with the highest pitch? Sound B is the highest pitched. Sound B has the most number of waves across the oscilloscope – it has the highest frequency and so has the highest pitch. BA

11 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Wave animation

12 © Boardworks Ltd of 20 © Boardworks Ltd of 36 8L Sound and Hearing Contents What is sound? Speed of sound The ear and hearing Summary activities Reflecting sound

13 © Boardworks Ltd of 20 © Boardworks Ltd of m START STOP 1. When you see the cymbals crash, press START. 2. When you hear the cymbals crash, press STOP. This investigation to calculate the speed of sound should be carried out in a quiet open space. Speed of sound experiment

14 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Experiment distance (m) time (s) speed (m/s) Record the results of the sound experiment. =294 m/s distance time speed = = Speed of sound experiment – results table How are these values used to estimate the speed of sound?

15 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Use the results of the cymbals experiment to calculate the average speed of sound. How does this calculation for the average speed of sound compare with the real speed? The speed of sound in air is about… What errors could have affected the results of the cymbals experiment? 340 m/s Do you think the speed of sound in water is the same as the speed of in air? Speed of sound experiment – results

16 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Sound in different states of matter Sound needs a substance to travel through and travels by particles vibrating. The particles in a solid are closer together than in a gas or a liquid. This means vibrations are more easily passed from particle to particle and so sound travels faster. gassolidliquid Sound waves travel fastest through solids. Which state of matter does sound travel fastest through?

17 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Sound need particles to travel and the type of substance affects the speed of sound. speed of sound (m/s) Speed of sound in different materials

18 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Which of these travel faster than the speed of sound in air? distance (m) time (s) speed (m/s) small aeroplane 6005 jet fighter9002 cheetah502.5 meteorite , Breaking the sound barrier! The jet fighter and the meteorite travel faster than the speed of sound in air – this is called breaking the sound barrier.

19 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Usually, you see lightning before you hear thunder. Light travels much faster than sound. The speed of light is… During a thunderstorm, thunder and lightning are created at the same time. Which do you notice first? How could you use thunder and the speed of sound to estimate how far away a thunderstorm is? 300, 000, 000 m/s How much faster is light than sound? Sound or light – which is faster?

20 © Boardworks Ltd of 20 © Boardworks Ltd of 36 8L Sound and Hearing Contents What is sound? Speed of sound The ear and hearing Summary activities Reflecting sound

21 © Boardworks Ltd of 20 © Boardworks Ltd of 36 The sound wave is reflected back from the surface. This is called an echo. What happens when a sound wave meets a hard flat surface? Reflected sound

22 © Boardworks Ltd of 20 © Boardworks Ltd of Use a starting pistol (or clapper board) to make a sound. 2. Measure the time taken between firing the pistol and hearing the echo. START 150 m Stand at least 100 m from a large, flat wall with a stop watch. STOP Echo experiment

23 © Boardworks Ltd of 20 © Boardworks Ltd of 36 How can you use this result to estimate the speed of sound? The sound of the starting pistol takes 0.92 s to travel a distance of 300 m. =326 m/s distance time speed = = Repeat the experiment several times to obtain an average. Echo experiment How does your calculation for the average speed of sound compare with the real value? compare with the real value?

24 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Questions on reflecting sound 1. What is a reflected sound called? an echo 2. Are hard or soft surfaces best at reflecting sound? 3. Why are there soft materials on the walls of cinemas and theatres? to reduce echoes 4. Name two animals that use echoes for navigation or communication. bats and dolphins hard surfaces

25 © Boardworks Ltd of 20 © Boardworks Ltd of 36 8L Sound and Hearing Contents What is sound? Speed of sound The ear and hearing Summary activities Reflecting sound

26 © Boardworks Ltd of 20 © Boardworks Ltd of 36 The ear and sound waves

27 © Boardworks Ltd of 20 © Boardworks Ltd of 36 1.Sound waves are collected by the ear lobe or pinna. 2.The waves travel along the ear canal. 3.The waves make the ear drum vibrate. 4.The small bones (ossicles) amplify the vibrations. 5.The cochlea turns these into electrical signals. 6.The auditory nerve takes the signals to the brain How does the ear hear?

28 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Set the volume and increase the frequency of the signal provided by the signal generator. 20 Hz to 20,000 Hz Humans can only hear sounds of certain frequencies. What is the hearing range of a healthy young person? The range of frequencies a person can hear is called their hearing range. Hearing range

29 © Boardworks Ltd of 20 © Boardworks Ltd of ,000 10,000 1, human dog elephant bat mouse dolphin Which animals hear the lowest and the highest frequencies? frequency (Hz) Comparing hearing ranges

30 © Boardworks Ltd of 20 © Boardworks Ltd of 36 We all have slightly different hearing ranges People lose the ability to hear sounds of high frequency as they get older. Almost 1 in 5 people suffer some sort of hearing loss. Temporary hearing loss may be caused by ear infections and colds, after which hearing recovers. Permanent hearing loss and deafness can be present at birth or occur if the ear is damaged or diseased. Does everyone have the same hearing range? Hearing ranges and hearing loss

31 © Boardworks Ltd of 20 © Boardworks Ltd of permanent ear damage can just be heard aircraft overhead decibels circular saw at 2m quiet countryside pin being dropped loud bell personal stereo Measuring loudness – the decibel scale

32 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Noise and its effects A noise is any unwanted sound. What one person considers noise another person might not. Can you name any examples? Noise can cause hearing problems. List three effects of noise. 2. nausea 1. headaches 3. deafness List three ways of reducing the effects of loud noise. 1. ear protectors 3. putting noisy machinery in insulated rooms 2. double glazing

33 © Boardworks Ltd of 20 © Boardworks Ltd of 36 8L Sound and Hearing Contents What is sound? Speed of sound The ear and hearing Summary activities Reflecting sound

34 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Glossary amplitude – The height of a wave, which shows how loud a sound is. cochlea – The part of the inner ear that changes vibrations into electrical signals which are then sent to the brain. decibel – The unit for measuring the loudness of sound (dB). eardrum – The thin membrane in the ear which vibrates when sound reaches it. frequency – The number of waves per second, which shows the pitch of a sound. hertz – The unit of frequency (Hz). 1 Hz = 1 wave per second. oscilloscope – An instrument that shows a picture of sound. pitch – How high or low a sound is. sound – A form of energy produced by vibrations, which is detected by the ears.

35 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Anagrams

36 © Boardworks Ltd of 20 © Boardworks Ltd of 36 Multiple-choice quiz


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