Transcription
KS3 Physics8L Sound andHearing1 of 3620 Boardworks Ltd 20052004
Contents8L Sound and HearingWhat is sound?Speed of soundReflecting soundThe ear and hearingSummary activities1 of 36202 Boardworks Ltd 20052004
What causes sound?Take a tuning fork and strike itagainst a block of wood.What do you observe?The tuning fork vibratesand you hear a sound.Sounds are made whenan object vibrates.1 of 36203 Boardworks Ltd 20052004
Good vibrations!What vibrates so that the following make sounds?violinstringsdrumskinvoice boxloudspeakercone1 of 36204 Boardworks Ltd 20052004
The bell-jar experimentPlace 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?The sound cannot be heardbecause there is no air insidethe bell jar (a vacuum).1 of 36205 Boardworks Ltd 20052004
Studying sound wavesSound waves can be studied with this type of equipment.loudspeakeroscilloscopesignal generatorA loudspeakerconvertssignals fromthe signalgenerator intosound waves.1 of 36206A signal generatorproduces differenttypes of signals.An oscilloscopeshows wavepatterns and allowsus to ‘see’ sound. Boardworks Ltd 20052004
Loudness and amplitudeA sound can be quiet or loud.quiet soundloud soundOn an oscilloscope trace, the loudness of a sound is shownby the height of the wave. This is called the amplitude.Which word should be crossed out in this sentence?The larger the amplitude of the wave on the trace,the louder/quieter the sound.1 of 36207 Boardworks Ltd 20052004
Which is the loudest?Which trace represents the loudest sound?ABSound A is the loudest.Sound A has the largest amplitude (i.e. the tallest waves),so it is the loudest of these two sounds.1 of 36208 Boardworks Ltd 20052004
Pitch and frequencyA sound can be high or low – this is the pitch of the sound.low pitch soundhigh pitch soundOn an oscilloscope trace, the pitch of a sound is shown byhow 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 oscilloscopetrace, the lower/higher the frequency and pitch.1 of 36209 Boardworks Ltd 20052004
Which is the highest?Which trace represents the sound with the highest pitch?ABSound B is the highestpitched.Sound B has the most number of waves across theoscilloscope – it has the highest frequency and sohas the highest pitch.1 ofof201036 Boardworks Ltd 20052004
Wave animation1 ofof201136 Boardworks Ltd 20052004
Contents8L Sound and HearingWhat is sound?Speed of soundReflecting soundThe ear and hearingSummary activities1 ofof201236 Boardworks Ltd 20052004
Speed of sound experimentThis investigation to calculate the speed of sound shouldbe carried out in a quiet open space.STARTSTOP0 0 : 0 0 30 04100 m1. When you see the cymbals crash, press START.2. When you hear the cymbals crash, press STOP.1 ofof201336 Boardworks Ltd 20052004
Speed of sound experiment – results tableRecord the results of the sound experiment.Experiment distance(m)1100time(s)0.34speed(m/s)294234How are these values used to estimate the speed of sound?distance100 294 m/sspeed time0.341 ofof201436 Boardworks Ltd 20052004
Speed of sound experiment – resultsThe speed of sound in air is about 340 m/sUse the results of the cymbals experimentto calculate the average speed of sound.How does this calculation for the average speed of soundcompare with the real speed?What errors could have affected the results of the cymbalsexperiment?Do you think the speed of sound in water is the sameas the speed of in air?1 ofof201536 Boardworks Ltd 20052004
Sound in different states of matterSound needs a substance to travel through and travels byparticles vibrating.Which state of matter does sound travel fastest through?solidliquidgasSound waves travel fastest through solids.The particles in a solid are closer together than in a gas ora liquid. This means vibrations are more easily passedfrom particle to particle and so sound travels faster.1 ofof201636 Boardworks Ltd 20052004
Speed of sound in different materialsSound need particles to travel and the type of substanceaffects the speed of sound.70006000speed of sound (m/s)60005000500040003000200010001450330350air at 0 Cair at 30 C0waterconcretesteelmaterial1 ofof201736 Boardworks Ltd 20052004
Breaking the sound barrier!Which of these travel faster than the speed of sound in 120jet fighter9002450cheetah502.520meteorite10 0000.3528,571The jet fighter and the meteorite travel faster than the speedof sound in air – this is called breaking the sound barrier.1 ofof201836 Boardworks Ltd 20052004
Sound or light – which is faster?During a thunderstorm,thunder and lightning arecreated at the same time.Which do you notice first?Usually, you see lightningbefore you hear thunder.Light travels much fasterthan sound.The speed of light is 300,000,000 m/sHow much faster is light than sound?How could you use thunder and the speed of sound toestimate how far away a thunderstorm is?1 ofof201936 Boardworks Ltd 20052004
Contents8L Sound and HearingWhat is sound?Speed of soundReflecting soundThe ear and hearingSummary activities1 ofof202036 Boardworks Ltd 20052004
Reflected soundWhat happens when a sound wave meets a hard flatsurface?The sound wave is reflected back from the surface.This is called an echo.1 ofof202136 Boardworks Ltd 20052004
Echo experimentStand 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.1 ofof202236 Boardworks Ltd 20052004
Echo experimentThe 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?distancespeed time 3000.92 326 m/sRepeat the experiment several times to obtain an average.How does your calculation for the average speed of soundcompare with the real value?1 ofof202336 Boardworks Ltd 20052004
Questions on reflecting sound1. What is a reflected sound called?an echo2. Are hard or soft surfaces best at reflecting sound?hard surfaces3. Why are there soft materials on the walls of cinemasand theatres?to reduce echoes4. Name two animals that use echoes for navigation orcommunication.bats and dolphins1 ofof202436 Boardworks Ltd 20052004
Contents8L Sound and HearingWhat is sound?Speed of soundReflecting soundThe ear and hearingSummary activities1 ofof202536 Boardworks Ltd 20052004
The ear and sound waves1 ofof202636 Boardworks Ltd 20052004
How does the ear hear?1.Sound waves arecollected by theear lobe orpinna.6.The auditory nervetakes the signalsto the brain.6412352.The wavestravel alongthe ear canal.5.The cochleaturns theseinto electrical4.The small bones3.The wavessignals.(ossicles) amplifymake the earthe vibrations.drum vibrate.1 ofof202736 Boardworks Ltd 20052004
Hearing rangeSet the volume and increase the frequency of the signalprovided by the signal generator.Humans can only hear sounds of certain frequencies.The range of frequencies a person can hear is called theirhearing range.What is the hearing range of a healthy young person?20 Hz to 20,000 Hz1 ofof202836 Boardworks Ltd 20052004
Comparing hearing rangesWhich animals hear the lowest and the highest human1 ofof202936dogbat elephant mouse dolphin Boardworks Ltd 20052004
Hearing ranges and hearing lossDoes everyone have the same hearing range?We all have slightly different hearing rangesPeople lose the ability to hear sounds of highfrequency as they get older.Almost 1 in 5 people suffer some sort ofhearing loss. Temporary hearing loss may be caused by ear infectionsand colds, after which hearing recovers. Permanent hearing loss and deafness can be presentat birth or occur if the ear is damaged or diseased.1 ofof203036 Boardworks Ltd 20052004
Measuring loudness – the decibel scaledecibelsaircraftoverhead160personal stereo140permanentear damage120100loudbell80quietcountryside6040pin beingdropped1 ofof203136200circular sawat 2mcan justbe heard Boardworks Ltd 20052004
Noise and its effectsA 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.1. headaches2. nausea3. deafnessList three ways of reducing the effects of loud noise.1. ear protectors2. double glazing3. putting noisy machinery in insulated rooms1 ofof203236 Boardworks Ltd 20052004
Contents8L Sound and HearingWhat is sound?Speed of soundReflecting soundThe ear and hearingSummary activities1 ofof203336 Boardworks Ltd 20052004
Glossary amplitude – The height of a wave, which shows how louda sound is. cochlea – The part of the inner ear that changes vibrationsinto 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 vibrateswhen sound reaches it. frequency – The number of waves per second, whichshows 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 isdetected by the ears.1 ofof203436 Boardworks Ltd 20052004
Anagrams1 ofof203536 Boardworks Ltd 20052004
Multiple-choice quiz1 ofof203636 Boardworks Ltd 20052004
1 of 209 of 36 Boardworks Ltd 2004 Boardworks Ltd 2005 Pitch and frequency A sound can be high or low –
