KS4 Physics

1. Sound KS4 Physics

2. Contents Sound What is sound? Structure of sound waves Hearing sound Ultrasound Summary activities

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

4. What vibrates so that the following make sounds? Good vibrations! violin strings drum skin voice box loudspeaker cone

5. longitudinal wave How does sound travel? How does sound reach your ear? When the drum skin is struck, it vibrates which causes the air beside the drum to vibrate. The compression and stretching of air particles creates a sound wave which is carried through the air to your ear. What type of wave is a sound wave?

6. The bell-jar experiment Place a ringing clock inside the bell jar and what happens? vacuum pump on There is air inside the bell jar so the sound can travel and be heard. Remove the air from the bell jar and what happens to the sound? With a vacuum inside the bell jar, the sound cannot be heard. Why?

7. You need a quiet open space at least 100m long to perform this investigation. 100m How fast does sound travel? START STOP 1. When you see the cymbals crash, press START. 2. When you hear the cymbals crash, press STOP.

8. 100 0.34 distance = = 294 m/s speed = time How fast does sound travel? Record the results of your sound experiments in a table. 100 0.34 294 How are these values used to estimate the speed of sound?

9. The speed of sound in air is about… How fast does sound travel? 340 m/s • Use the results of the cymbals experiment to calculate your average speed of sound. How does your calculation for the average speed of sound comparewith the real speed? What errors could have affected the results of your cymbals experiment? Do you think the speed of sound in water is the same as it is in air?

10. Different speeds of sound

11. solid liquid gas Sound and states of matter Sound waves need a substance to travel through. What are all substances made of? particles What is the particle model of a solid, a liquid and a gas? solid In which state are the particles closest together? gas In which state are the particles furthest apart?

12. Sound waves travel by particles vibrating. What state does sound travel fastest through and why? solid liquid gas Sound and states of matter Sound waves travel fastest through solids. 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 waves travels faster.

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

14. Which of these travel faster than the speed of sound in air? Breaking the sound barrier! 120 450 20 28 571 The jet fighter and the meteorite break the sound barrier. What does this mean?

15. What happens when a sound wave meets a hard flat surface? Reflected sound waves The sound wave is reflected back from the surface. What type of sound does this produce? echo

16. Stand at least 100m from a large, flat wall with a stop watch. Experiment on echoes START 150m STOP 1. Use a starting pistol (or clapper board) to make a sound. 2. Measure the time taken between firing the pistol and hearing the echo. How far does the sound travel?

17. The sound of the starting pistol takes 0.92s to travel a distance of 300m. 300 0.92 distance = = 326 m/s How does your calculation for the average speed of sound speed = time comparewith the real speed? Experiment on echoes How can you use this result to estimate the speed of sound? Repeat the experiment several times to obtain an average.

18. Echoes and reflection What do we call reflected sound? an echo Are hard or soft surfaces best at reflecting sound? Hard surfaces produce strong echoes. How are echoes reduced in cinemas and theatres? By using soft materials on the walls such as curtains. Name two animals that use echoes for navigation or communication. bats and dolphins

19. Contents Sound What is sound? Structure of sound waves Hearing sound Ultrasound Summary activities

20. Sound waves can be studied with this type of equipment. Studying sound waves loudspeaker oscilloscope signal generator Which piece of equipment: • produces signals over a range of frequencies and of varying amplitudes? • converts signals into sound waves? • is used to study the frequency and loudness of a sound? signal generator loudspeaker oscilloscope

21. quiet sound loud sound Why sound is quiet or loud? What is the difference between the sound wave of a quiet sound and a loud sound? The loud sound has taller waves. The louder the sound, the greater the amplitude. What would the sound wave of a very loud sound look like?

22. Which trace represents the loudest sound? A B Which is the loudest? Sound A is the loudest. Sound A has the largest amplitude, which means the wave has more energy and so the sound is louder.

23. What is the difference between the sound wave of a low pitch sound and a high pitchsound? low pitch sound high pitch sound Why sound is low pitch or high pitch? The high pitch sound has a shorter wavelength, so more waves are visible. It has higher frequency waves. What would the sound wave of a very low sound look like?

24. Which trace represents the sound with the highest pitch? A B Which is the highest? Sound B is the highest pitched. Sound B has the shortest wavelength and the most number of waves visible, so it has the highest frequency.

25. Wave animation

26. Contents Sound What is sound? Structure of sound waves Hearing sound Ultrasound Summary activities

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

28. How does the ear hear?

29. Can we hear all frequencies? Set the volume and increase the frequency of the signal provided by the signal generator. Humans cannot hear sounds of every frequency. The range of frequencies you can hear is called your hearing range. What is the hearing range of a healthy young person? 20 Hz to 20,000 Hz

30. Do we have the same hearing? Does everyone have the same hearing range? We all have slightly different hearing ranges but almost 1 in 5 people suffer some sort of hearing loss. Temporaryhearing loss may be caused by ear infections and colds, after which hearing recovers. Permanenthearing loss and deafness can be present at birth or occur if the ear is damaged or diseased. People lose the ability to hear sounds of high frequency as they get older. Which end of their hearing range will be affected?

31. Comparing hearing ranges Do all animals have the same hearing range? 100,000 10,000 1,000 100 10 1 0 frequency (Hz) elephant mouse human dog dolphin bat

32. The loudness of a sound is measured in decibels (dB). How is loudness measured? 0dB = quietest audible sound (near total silence) 10dB = 10 times more powerful than the quietest sound 20dB = 100 times more powerful than the quietest sound How much more powerful than the quietest sound is 30dB? 1,000 times A whisper is 30dB and normal conversation is 60dB. How much more powerful is normal conversation compared to a whisper? 1,000 times

33. When is sound dangerous? Any sound above 85 dB can damage hearing. You know you are listening to 85 dB sound if you have to raise your voice to be heard. What might also influence hearing loss? The amount of time spent listening to a loud sound also causes hearing problems. Any 140 dB sound causes pain and immediate damage! More than two hours of 100 dB sound can damage your ears. Why are there laws about the maximum levels of sound that people should be exposed to at work?

34. What is noise? A noise is any unwanted sound. What one person considers noise another person might not. Can you name any examples? List three effects of noise. headaches nausea deafness List three ways of reducing the effects of loud noise. ear protectors double glazing putting noisy machinery in insulated rooms

35. personal stereo aircraft overhead loud bell quiet countryside circular saw at 2m pin being dropped can just be heard How loud is loud? decibels 160 140 120 100 80 60 40 20 0 permanent ear damage

36. The results of a hearing tested are shown on an audiogram. loud sound moderate sound soft sound intensity ofsound (dB) frequency of sound (Hz) low pitch high pitch How is hearing tested? The audiogram shows hearing sensitivity for different frequencies (pitch) at different intensities (volume). It records the softest sound heard at each pitch .

37. Which audiogram trace represents optimal hearing and which represents impaired hearing? frequency of sound (Hz) Testing hearing impaired hearing intensity of sound (dB) optimal hearing

38. Contents Sound What is sound? Structure of sound waves Hearing sound Ultrasound Summary activities

39. The upper frequency limit of human hearing 20,000 Hz. What is ultrasound? Any high frequency sound above 20 kHz is called… ultrasound Whales and dolphins communicate using ultrasound. Why does a dog whistle vibrate at ultrasound frequencies? Can you name another human use of ultrasound?

40. Which of the following does not use ultrasound? Using ultrasound imaging fetuses dolphins jewellery cleaning ultrasonic toothbrush viewing kidney stones bats ultrasonic cleaning echo location submarines It’s a trick question! All of the above involve ultrasound. High frequencies can be very useful!

41. fetus at 10 weeks fetus at 20 weeks Using ultrasound in medicine Ultrasound is the name given to a medical technique. It uses high-frequency sound waves to produce images of inside the body without opening up the body. Why is ultrasound used for scanning fetuses instead ofX-rays, which would give a clearer picture? X rays are more energetic and penetrating and are a lot more dangerous, they could cause damage to the growing baby.

42. Ultrasound, like all sound, is reflected when it meets different boundaries. So how is this used for imaging? How does ultrasound imaging work? An ultrasound machine transmits high-frequency sound waves into the body. These sound waves are reflected different amounts by different tissues. The reflected waves are detected by a receiver. A computer turns the distance and intensities of these echoes into a two-dimensional image.

43. Contents Sound What is sound? Structure of sound waves Hearing sound Ultrasound Summary activities

44. Glossary • amplitude – How loud a sound is, which depends on the height of the peak of a sound wave from its rest position. • audiogram – A graphical recording of hearing ability at various sound frequencies. • echo – The sound produced when sound waves are reflected from a surface and heard shortly after the original. • frequency – The number of waves per second, which shows the pitch of a sound. It is measured in hertz (Hz). • oscilloscope – A device that displays electronic signals (waves and pulses) on a screen. • pitch – How high a sound is, which depends on the frequency of the sound wave vibrations. • ultrasound – Sound waves with very high frequencies above the range of human hearing, which are used for producing images of inside the body.

45. Anagrams

46. Sound multiple choice