# Sound What is sound? It is made when an object or material vibrates. A vibration is a fast, backwards and forwards movement that repeats many times.

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Sound

What is sound? It is made when an object or material vibrates. A vibration is a fast, backwards and forwards movement that repeats many times. A sound wave is produced when air molecules are alternately squashed together and pulled apart. Sound is a form of energy.

What is sound? rarefaction (spreading out) compression (squashing) energy moves this way particles vibrate this way Sound is a longitudinal wave, like the wave shown on this slinky. The molecules vibrate in the same direction that the energy of the wave travels in. Slinky or long spring

Making Sounds A sound is made when an object or material VIBRATES. Take, for example, a guitar: To make a sound with a guitar a string has to vibrate. We can raise the pitch of the sound a guitar makes by doing three things: 1) _________ the length of the string 2) _________ the string 3) Using a _________ string We can make the sound louder by ________ the string harder Words – tightening, thinner, increasing, plucking

Making Sounds A sound is made when an object or material VIBRATES. Take, for example, a guitar. To make a sound with a guitar a string has to vibrate. We can raise the pitch of the sound a guitar makes by doing three things: 1) _________ the length of the string 2) _________ the string 3) Using a _________ string We can make the sound louder by ________ the string harder Words – tightening, thinner, increasing, plucking tightening thinner increasing plucking

Frequency and pitch 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. The greater the number of waves across the oscilloscope trace, the lower / higher the frequency and pitch. 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. Frequency and pitch 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?

Frequency and pitch Frequency = the number of sound vibrations set up in 1 second and is measured in Hertz (Hz). Pitch = how high or low the sound is (depends on how rapidly the ‘sound producer’ vibrates).

Frequency and pitch When you pluck the top string of a guitar, it vibrates 660 times in 1 second. What is the frequency of the sound it makes? Answer = 660Hz When you pluck the bottom string, it vibrates only 165 times each second. What is the frequency of the sound it makes? Answer = 165Hz What is the connection between frequency of a sound and its’ pitch? Answer: The top string makes a higher pitched sound than the bottom one. Therefore the higher frequency of a sound, the higher is its’ pitch.

Frequency and pitch When you pluck the top string of a guitar, it vibrates 660 times in 1 second. What is the frequency of the sound it makes? Answer = 660Hz When you pluck the bottom string, it vibrates only 165 times each second. What is the frequency of the sound it makes? Answer = 165Hz What is the connection between frequency of a sound and its’ pitch? Answer: The top string makes a higher pitched sound than the bottom one. Therefore the higher frequency of a sound, the higher is its’ pitch. When you pluck the top string of a guitar, it vibrates 660 times in 1 second. What is the frequency of the sound it makes? When you pluck the bottom string, it vibrates only 165 times each second. What is the frequency of the sound it makes? What is the connection between frequency of a sound and its’ pitch?

Amplitude Sounds can vary in ‘loudness’. A loud sound has more energy than a quiet sound. The loudness of a sound is its’ amplitude. Large vibrations cause a loud (high amplitude) sound.

The larger the amplitude of the wave on the trace, the louder / quieter the sound. Loudness and amplitude 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?

The larger the amplitude of the wave on the trace, the louder / quieter the sound. Loudness and amplitude 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?

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.

Using an oscilloscope An oscilloscope can be used to compare the amplitude and frequency of different sound waves.

Using an oscilloscope 1) Quiet sound, low frequency: 2) Quiet sound, high frequency: 3) Loud sound, low frequency: 4) Loud sound, high frequency:

How does sound travel? Sound travels as a series of vibrations through a material. Robert Boyle In 1705, Francis Hawksbee showed a famous experiment first performed by Robert Boyle in 1660 – the bell in a jar experiment. A pump was used to remove all of the air from the bell jar to form a vacuum.

Remove the air from the bell jar and what happens to the sound? How does sound travel? 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- it is a vacuum. vacuum pump on

How does sound travel? As we know, sound waves are formed when something vibrates. But how does the sound reach our ears? 1) An object makes a sound by vibrating 2) The vibrations pass through air by making air molecules vibrate 3) These vibrations are picked up by the ear Air molecules

How does sound travel? 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?

How does sound travel? A vacuum is an empty space that contain no particles at all. Sound cannot travel through a vacuum because there are no particles to vibrate and carry the sound wave.

How does sound travel? What is a vacuum? The Sun is an exploding ball of hot gases with a surface temperature of 5500C. Space is a vacuum. Why can we see the Sun but not hear the sound it makes? Astronauts sometimes leave their spacecraft to repair a faulty satellite. Why do they use a radio system to talk to each other?

The speed of sound The speed of sound can be calculated using the following equation:- Speed of sound = distance between 2 people ÷ time taken for sound to travel this distance

Speed of sound The speed of sound in air is around 330 m/s. What happens when sound travels through different materials? Material Speed of sound (in m/s) Conclusion The denser the material, the faster sound travels through it

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 material

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 meteorite10 0000.35 120 450 28,571 20 Breaking the sound barrier! 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.

)))) How does the ear work? Sound Waves - air vibrates and moves towards the ear Inner ear bones - the vibrating ear drum makes the inner ear bones move like levers Ear drum - the vibrating air causes the ear drum to vibrate Cochlea - the bones movement is transferred to fluid which moves hairs Auditory nerve - carries electrical messages to the brain

How does the ear work?

100,000 10,000 1,000 100 10 1 0 human Which animals hear the lowest and the highest frequencies? frequency (Hz) Comparing hearing ranges dogbatelephantmousedolphin

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

160 140 120 100 80 60 40 20 0 decibels Measuring loudness – decibel scale Personal stereo Loud bell Aircraft overhead Circular saw at 2m Quiet countryside Pin being dropped Can just be heard PERMANENT EAR DAMAGE

Medical treatment e.g. kidney stones, sports injuries. Ultrasound Ultrasound ( high frequency sound) is the region of sound above 20,000Hz – it cannot be heard by humans. There are a number of uses for ultrasound: Pre-natal screening to check the development of unborn babies Cleaning delicate objects or machinery that cannot be dismantled. Checking for cracks in metal structures e.g. aircraft.

How does ultrasound work? Ultrasonic waves are partly _________ at the boundary as they pass from one _______ to another. The time taken for these reflections can be used to measure the _______ of the reflecting surface and this information is used to build up a __________ of the object. Words – depth, reflected, picture, medium

How does ultrasound work? Ultrasonic waves are partly _________ at the boundary as they pass from one _______ to another. The time taken for these reflections can be used to measure the _______ of the reflecting surface and this information is used to build up a __________ of the object. Words – depth, reflected, picture, medium depth reflected picture medium

Other uses for sound Sonar, using sound waves, is used to measure the depth of water. Echoes of sound waves are also used to detect places where oil deposits might be found.

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