2Waves: Sound What is sound? Sound and reflection ContentsWaves: SoundWhat is sound?Sound and reflectionStructure of sound wavesHearing soundUltrasound
3Sounds are made when an object vibrates. What causes sound?Take a tuning fork and strike it against a block of wood. What do you observe?The tuning fork vibrates and you hear a sound.Sounds are made when an object vibrates.
4Good vibrations! What vibrates so that the following make sounds? violin stringsdrum skinvoice boxloudspeaker cone
5How does sound travel? How does sound reach your ear? longitudinal waveWhen 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?
6The bell-jar experiment Place a ringing clock inside the bell jar and what happens?There is air inside the bell jarso the sound can travel and be heard.vacuumpump onRemove the air from the bell jarand what happens to the sound?With a vacuum inside the bell jar,the sound cannot be heard. Why?
7How fast does sound travel? You need a quiet open space at least 100 m longto perform this investigation.STARTSTOP100 m1. When you see the cymbals crash, press START.2. When you hear the cymbals crash, press STOP.
8How fast does sound travel? Record the results of your sound experiments in a table.sounddistance (m)time(s)speed(m/s)12341000.34294How are these values used to estimate the speed of sound?distancetimespeed ==1000.34=294 m/s
9How fast does sound travel? The speed of sound in air is about…340 m/sUse the results of the cymbals experimentto calculate your average speed of sound.How does your calculation for the average speed of sound compare with 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?
11Sound and states of matter Sound waves need a substance to travel through.What are all substances made of?particlessolidliquidgasWhat is the particle model of a solid, a liquid and a gas?In which state are the particles closest together?solidIn which state are the particles furthest apart?gas
12Sound and states of matter Sound waves travel by particles vibrating.What state does sound travel fastest through and why?solidliquidgasSound 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.
13Sound or light – which is faster? During a thunderstorm, thunder and lightning are created at the same time.Which do you notice first?Usually, you see lightning before you hear thunder . Light travels much faster than sound.m/sThe 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?
14Breaking the sound barrier! Which of these travel faster than the speed of sound in air?distance(m)time(s)speed(m/s)small aeroplane6005jet fighter9002cheetah502.5meteorite10 0000.351204502028 571The jet fighter and the meteorite break the sound barrier. What does this mean?
15Waves: Sound What is sound? Sound and reflection ContentsWaves: SoundWhat is sound?Sound and reflectionStructure of sound wavesHearing soundUltrasound
16Reflected sound waves What happens when a sound wave meets a hard flat surface?The sound wave is reflected back from the surface.What type of sound does this produce?echo
17Experiment on echoes START STOP Stand at least 100 m from a large, flat wall with a stop watch.START150 mSTOP1. Use a starting pistol (or clapper board) to make a sound.2. Measure the time taken between firing the pistol andhearing the echo. How far does the sound travel?
18Experiment on echoes distance time speed = = 300 0.92 = 326 m/s The sound of the starting pistol takes 0.92 sto travel a distance of 300 m.How can you use this result to estimate the speed of sound?distancetimespeed ==3000.92=326 m/sRepeat the experiment several times to obtain an average.How does your calculation for the average speed of sound compare with the real speed?
19Echoes 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
20Waves: Sound What is sound? Sound and reflection ContentsWaves: SoundWhat is sound?Sound and reflectionStructure of sound wavesHearing soundUltrasound
21Studying sound wavesSound waves can be studied with this type of equipment.loudspeakeroscilloscopesignal generatorWhich 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 generatorloudspeakeroscilloscope
22Why sound is quiet or loud? What is the difference between the sound wave of a quiet sound and a loud sound?quiet soundloud soundThe 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?
23Which is the loudest? A B Which trace represents the loudest sound? Sound A is the loudest.Sound A has the largest amplitude, which means the wave has more energy and so the sound is louder.
24Why sound is low pitch or high pitch? What is the difference between the sound wave of a low pitch sound and a high pitch sound?low pitch soundhigh pitch soundThe 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?
25Which is the highest?Which trace represents the sound with the highest pitch?ABSound B is the highest pitched.Sound B has the shortest wavelength and the most number of waves visible, so it has the highest frequency.
27Waves: Sound What is sound? Sound and reflection ContentsWaves: SoundWhat is sound?Sound and reflectionStructure of sound wavesHearing soundUltrasound
28How does the ear hear?1.Sound waves are collected by the ear lobe or pinna.6.The auditory nervetakes the signalsto the brain.6412352.The waves travel along the ear canal.5.The cochlea turns these into electrical signals.3.The waves make the ear drum vibrate.4.The small bones (ossicles) amplify the vibrations.
30Can 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 Hz
31Do 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.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.People lose the ability to hear sounds of high frequency as they get older.Which end of their hearing range will be affected?
32Comparing hearing ranges Do all animals have the same hearing range?10 0001 000100101frequency(Hz)Frequency low (Hz) high (Hz)HumanDogBatElephantMouseCatDolphinhumandogbatelephantmousedolphin
33How is loudness measured? The loudness of a sound is measured in decibels (dB).0 dB = quietest audible sound (near total silence)10 dB = 10 times more powerful than the quietest sound20 dB = 100 times more powerful than the quietest soundHow much more powerful than the quietest sound is 30 dB?1000 timesA whisper is 30 dB and normal conversation is 60 dB.How much more powerful is normal conversation compared to a whisper?1000 times
34When is sound dangerous? Any sound above 85 dB can damage hearing.You know you are listening to 85 dB soundif you have to raise your voice to be heard.What might also influence hearing loss?The amount of time spent listening to a loud soundalso 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?
35What 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.headachesnauseadeafnessList three ways of reducing the effects of loud noise.ear protectorsdouble glazingputting noisy machinery in insulated rooms
36How loud is loud? 160 140 120 100 80 60 40 20 decibels personal stereo personal stereopermanent ear damageaircraftoverheadloud bellcircular sawat 2mquietcountrysidepin beingdroppedcan just be heard
37How is hearing tested?The results of a hearing tested are shown on an audiogram.frequency of sound (Hz)intensity of sound (dB)loud soundmoderate soundsoft soundlow pitch high pitchThe audiogram shows hearing sensitivity for different frequencies (pitch) at different intensities (volume).It records the softest sound heard at each pitch .
38Testing hearingWhich audiogram trace represents optimal hearing and which represents impaired hearing?frequency of sound (Hz)intensity of sound (dB)impairedhearingoptimalhearing
39Waves: Sound What is sound? Sound and reflection ContentsWaves: SoundWhat is sound?Sound and reflectionStructure of sound wavesHearing soundUltrasound
40What is ultrasound? ultrasound The upper frequency limit of human hearing Hz.Any high frequency sound above 20 kHz is called…ultrasoundWhales and dolphins communicate using ultrasound.Why does a dog whistle vibrate at ultrasound frequencies?Can you name another human use of ultrasound?
41ultrasonic toothbrush Using ultrasoundWhich of the following does not use ultrasound?imaging fetusesdolphinsjewellery cleaningultrasonic toothbrushviewing kidney stonesbatsultrasonic cleaningecho locationUse the internet or research books to find out about other uses of ultrasound.These keywords should help.submarinesIt’s a trick question! All of the above involve ultrasound.High frequencies can be very useful!
42Using 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.fetus at 10 weeksfetus at 20 weeksX rays are more energetic and penetrating and are a lot more dangerous, they could cause damage to the growing baby.Why is ultrasound for scanning fetuses instead of X rays which would give a clearer picture?
43How does ultrasound imaging work? Ultrasound, like all sound, is reflected when it meets different boundaries. So how is this used for imaging?An ultrasound machine transmits high-frequency sound waves into the body.These sound waves are reflected different amounts by different tissues.The reflected waves aredetected by a receiver.A computer turns the distanceand intensities of these echoesinto a two-dimensional image.