Sound Junior Science Physics Revised Science Syllabus Extract

Sound Junior Science: Physics

Revised Science Syllabus Extract Main Topic Sub-topics 3 B 5 • transmission of sound • speed of sound • vibrations and sound • reflection of sound • echoes • sound detection in the ear • sound levels • hearing protection Sound 3 B 6 Reflection of sound Hearing

Learning Outcomes for 3 B 5 and 3 B 6 On completion of this section, students should be able to OP 40 show that sound is a form of energy, and understand that sound is produced by vibrations OP 41 show that sound transmission requires a medium and echoes are reflected sound

Learning Outcomes for 3 B 5 and 3 B 6 On completion of this section, students should be able to: OP 42 understand that the ear detects sound vibrations and that exposure to very loud sounds can cause damage to the hearing OP 43 recall that the speed of sound is less than the speed of light OP 44 explain the time lag between seeing and hearing the same event

Equipment and Resources • Shatter resistant rulers • Bell jar, sound source – alarm clock, vacuum pump

Sound Can you guess what these sounds are? Beluga Whale Shrimp

SOUND What is sound? • Sound is a form of energy • Sound energy can be converted into other energy forms

Sound energy Kinetic Energy

Sound energy (contd. ) Sound energy can be converted into other energy forms Sound energy Electrical energy

How is sound created? Sound is created when objects vibrate

Vibrations • Sound is produced by vibrations of the air molecules • A sound wave is just a moving pattern of changes in air pressure

What is a sound wave? Sound wave Vibrating ruler Pressure Compression Rarefaction Time

Transmission of sound • Sound requires a medium in order to be transmitted • Sound can be transmitted through a solid, liquid or gas • Sound cannot travel in a vacuum

Non-mandatory experiment to show Sound needs a medium in which to travel

What are echoes? • Sound can be reflected off surfaces • Echoes are sounds that are reflected from a surface • Sound reflection can be used to calculate distance

How do bats use sound? Echolocation

What is the speed of sound? • Speed of sound differs in different materials • Speed of sound in air at average temperatures and average pressure is approximately 340 m/s

Speed of sound (contd. ) • Sound does not travel through all materials at the same speed • Sound travels through water at approximately 1500 m/s • Sound travels through iron at approximately 6000 m/s

The speed of sound and the speed of light • Speed of sound is much smaller than the speed of light • Speed of sound 350 m/s • Speed of light 300 000 m/s • Calculate the distance by counting the seconds

Seeing an event before we hear it • Fireworks • Waves crashing on a beach in the distance

How do humans create sound? • Sound is produced by air rushing from your lungs past your vibrating vocal chords • These vibrations caused fluctuations in the rushing air, which formed a sound wave

How do we hear sound? • The vibrations travel through the air to our ears • Our eardrums vibrate with the sound • The vibrations are passed on through the ear, changed to electrical energy and transmitted to the brain • The brain then interprets and gives the sound meaning

Sound Can you guess what these sounds are? Frog Humpback whale

Hearing Damage How much sound causes permanent damage? 140 1 minute 120 15 minutes 100 Below this level (70 d. B) – hearing damage negligible 80 60 40 20 0 d. B

Sound Level is measured in Decibels Source of sound or noise Jet taking off at distance of 30 m Threshold of pain Disco loudspeaker 3 m away Pneumatic drill at road works 10 m away Busy street traffic Ordinary conversation Average whisper Threshold of hearing Sound level (in decibels) 140 120 100 70 60 20 0

Noise Protection • Mandatory ear protection • Ear muffs or ear plugs • Required in certain work environments where sound > 70 d. B

Assessment of student understanding • Combination of homework and a class quiz Homework • An automatic focus camera is able to focus on objects by use of an ultrasonic sound wave. The camera sends out sound waves which reflect off distant objects and return to the camera. A sensor detects the time it takes for the waves to return and then determines the distance an object is from the camera. If a sound wave (speed = 340 m/s) returns to the camera 0. 150 seconds after leaving the camera, how far away is the object?

Class Quiz - Sound 1. 2. 3. 4. 5. 6. 7. 8. What is sound? Give an example of sound energy being converted into another energy form? How is sound produced? What does sound need in order to be transmitted? Why is there no sound in a vacuum? What is an echo? What is name used for the technique whereby some animals use sound for location? What is the approximate speed of sound in air?

Class Quiz – Sound (contd. ) 9. 10. 11. 12. 13. The speed of sound in air can change with changes in _____ and ______ ? Through which of the following materials would sound travel faster (a) air, (b) water (c) iron Why does sound travel faster in iron than in air? During a storm a person hears the thunder before seeing the lightening, Why? Why do people who work in noisy environments wear protection?

BIBLIOGRAPHY • Websites • http: //www. acoustics. salford. ac. uk/schools/lesson 4/fl ash/waves 1. swf • http: //www. colorado. edu/physics/phet/webpages/simulations-base. html • http: //www. coolnotions. com/AGifs. htm • http: //www. findsounds. com/ISAPI/search. dll • http: //www. gifanimations. com/action/Image. Display? gr oup=2&category=155&index=29&dir=stay • http: //www. harrythecat. com/graphics/b. html

BIBLIOGRAPHY (contd. ) • Http: //www. juniorscience. ie • http: //www. oceanlink. island. net/oinfo/acoustics/Acoustic. Accompl ish. html#Anchor-The-49575 • http: //www. partnersinrhyme. com/soundfx/carsoundfx. shtml • http: //www. physics. brown. edu/physics/demopages/Demo/waves /demo/3 b 3030. htm • http: //science. howstuffworks. com/hearing 1. htm • http: //www. sounddogs. com/searchresults. asp • Textbook – Exploring Science , 2003 O’Callaghan, M. , Reilly, S. and Seery A. , The Educational Company