Presentation on theme: "Teacher’s Notes A slide contains teacher’s notes wherever this icon is displayed - To access these notes go to ‘Notes Page View’ (PowerPoint 97) or ‘Normal."— Presentation transcript:
2Teacher’s NotesA slide contains teacher’s notes wherever this icon is displayed -To access these notes go to ‘Notes Page View’ (PowerPoint 97) or ‘Normal View’ (PowerPoint 2000).Notes Page ViewNormal ViewFlash FilesA flash file has been embedded into the PowerPoint slide wherever this icon is displayed –These files are not editable.
3What causes sound?The tuning fork vibrates and you hear a sound.All sounds are caused by vibrations.Take a tuning fork and strike it against a block of wood, what do you observe?
4Music What vibrates when you sing? Your voice-box. What vibrates when you play a violin?The strings
5The Bell-jar experiment What happens when the air is removed from the bell-jar? Sound waves are vibrations and so need a substance to travel through. With air inside, the sound can be heard.With nothing inside [a vacuum], the sound can’t be heard.
6Sound : How fast does it travel? You need a quiet open space at least 100m long to perform this investigation.STOPSTART> 100m1) When you see the cymbals crash, press START.2) When you hear the cymbals crash, press STOP. Write your results in a table like this:
7Sound : How fast does it travel? Calculate your average speed of sound :Av. = [try 1 + try 2 + try 3 + try 4] 4. What errors could have crept into your results?
8Sound : How fast does it travel? Sound waves need particles in order to travel.The substance that the sound travels through affects the speed of sound greatly.Speed of sound [m/s]
9Travelling soundSound travels by particles vibrating. To understand this better you need to remember what the particles look like in a solid, liquid and a gas:solidliquidgasWhich state does sound travel fastest through? Why?In which state are the particles closest together?Sound travels fastest through solids because the particles are closer together than in a liquid and a gas, so the vibrations are more easily passed from particle to particle.solidIn which state are the particles furthest apart?gas
10Sound : How fast does it travel? Most of us have seen thunder storms - which comes first, the thunder or lightning? The lightning gets to our eyes before the thunder reaches our ears.1) Thunder & lightning are made at the same time so we deduce that light travels much faster than sound.2) In fact light travels so fast that:the time between seeing the flash and hearing the bang = time taken for sound to travel.
11Reflection : echoes You should remember that sound is produced by a vibration and travels as a longitudinal wave………..and that sound travels at different speeds through different substances [or media] Sound waves reflect off hard, smooth surfaces to produce echoes
12Using echoes What do we call reflected sound? an echo Which surfaces are the best at reflecting sound:HARD or SOFT ?How are echoes reduced in cinemas and theatres?By using soft materials on the walls such as curtains.Name two animals that use echoes?Bats and Dolphins
13START STOP Reflection : Echoes 150m Stand at least 100m from a large, straight wall Measure the distance from you to the wall Use a starting pistol [or clapper board] to make a soundSTARTSTOP Measure the time taken between firing the pistol and hearing the echo Remember, this is ‘two way travel time’ [twtt]
14SPEED = DISTANCE TIME v = 300 0.92 v = 326 m/s Reflection : Echoes The sound takes 0.92s to travel 300m Remember the formula for speed?SPEED = DISTANCE TIMEv = 0.92v = m/s Repeat this several times to obtain an average For the Higher Tier paper you will need to be able to change the subject of the formula
15 Reflection : questions 120 450 28571 20 Which of these travel faster than the speed of sound in air?
16Studying soundLoudspeakers convert the signal from the signal generator into sound waves.The oscilloscope allows us to study the frequency and loudness of a sound.Signal generators can produce signals over a range of frequencies and of varying amplitudes.
17The more waves you can see, the higher the pitch/frequency. Pitch (or frequency) A high pitch sound. A low pitch sound.The shorter/longer the wavelength of the wave on the trace; the lower/higher the frequency of the sound.The more waves you can see, the higher the pitch/frequency.
18Which trace represents the highest pitched sound? Oscilloscope tracesWhich trace represents the highest pitched sound?AB‘A’ is the highest pitched sound because it has the shortest wavelength/most number of waves visible.
19The bigger the waves you can see, the louder the sound. Loudness A quiet sound. A louder sound.The larger/smaller the amplitude of the wave on the trace, the louder/quieter the sound.The bigger the waves you can see, the louder the sound.
20Which trace represents the loudest sound? Oscilloscope tracesWhich trace represents the loudest sound?AB‘B’ Is the loudest sound because it has the largest amplitude.The larger the amplitude the more energy a wave has.The more energy it has, the louder the sound.
22Sound : What can I hear? Increase the frequency of the signal provided by a signal generator whilst keeping the volume the same.20 The lowest frequency I can hear is ________ Hz The highest frequency I can hear is ________ Hz20 000
23Sound : Are we all the same? You have just found your hearing range - could everyone hear exactly the same frequencies as you?We all have slightly different hearing ranges but almost 1 in 5 people suffer some sort of hearing loss. This changes with age. A baby has a wider range than an older person. Temporary hearing loss may be caused by ear infections and colds and hearing recovers. Permanent hearing loss and deafness can be present at birth or occur if the ear is damaged or diseased.
24Sound : Are we all the same? Hearing is tested using an audiometer and the results are shown on an audiogram.Hearing Loss [dB]
25Sound : Hearing Ranges Animal Which animal can hear the highest frequency?Which animal can hear the lowest frequency?mothspigeons
26Sound : The ear 1. Sound waves are collected by the ear lobe or pinna. 6. The auditory nerve takes the signals to the brain.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 the vibrations into electrical signals.
27Sound : The ear 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.
29Sound : How loud are sounds? 1501401201008060402010Personal stereoAircraft overheadPermanent ear damageLoud bellA circular saw at 2mQuiet countrysidePin being droppedCan just be heard
30What is noise?What you might not consider noise, loud music for example, other people might.A noise is any unwanted sound.What are the effects of noise?1. _________2. _________3. _________4. _________DeafnessVomitingHow can you reduce the effects of loud noise?___________________________________________________HeadachesNauseaEar protectorsDouble glazingPutting noisy machinery in insulated rooms
31What is the upper range of human hearing? 20 Hz200 Hz2 000 HzHz
32What causes all sounds?VibrationsReflectionsRefractionsHeat
33Which of the following can sound not travel through? LiquidVacuumSolidGas
34A ship releases an echo sounding and 4 seconds later receives a signal from the seabed, how deep is the sea? (speed of sound in water is 1500 m/s)6000m375m750m3000m
35Which of the following is not a use of ultrasound? Prenatal scanningQuality control in industryCleaning delicate machineryCooking food