Sound

1. Sound What is it, and how does it affect us?

2. Sound KWL What do you wonder/ want to know about? What do you know about sound? What have you learned about sound? • 3 things minimum! • Be specific//give details! • 3 things minimum! • Where do/have you encountered sound in your everyday life? • Be specific//give details! • Answer this section throughout the unit, any time you learn something new or cool! • Be specific//give details!

3. Questions of the Week • What is sound? • What influences the speed of sound?

4. Sound is a disturbance that travels through a medium as a longitudinal wave. These waves have compressions and rarefactions (similar to crests and troughs in transverse waves) Sound can travel in solid, liquid and gas… … but it cannot travel in a vacuum (empty space). Why not? Sound waves behave like other waves eg. they reflect (bounce), refract (change direction and speed), diffract (bend around obstacles), and interfere Sound

5. Speed of Sound Waves • The speed of sound depends on the properties of the medium the waves travel through. • There are 3 factors or properties that influence the speed of sound: • 1) Elasticity - the ability of a material to bounce back after being disturbed. • Waves travel faster if there’s high elasticity • Solids are more elastic than liquids or gases • Elasticity is the most important of the 3 factors • At 20°C, the speed of sound is around: • Air - 340 m/s • Water – 1500 m/s (~4.3X faster than air) • Steel - 5200 m/s (~15X faster than air)

6. Speed of Sound Waves • 2) Density - the amount of mass per unit of volume (space) • Speed depends on how close particles are. • Sound travels slower in denser mediums because particles don’t move as fast.  In which box (A or B) would sound travel fastest? Why? • 3) Temperature – the amount of kinetic energy that molecules in matter have. • The higher the temperature, the faster sound travels Remember that molecules move faster when they have more energy (temperature) • Sound travels slower at lower temperatures

7. Sound Videos • BrainPop (at school only) • Fun Science with Charlie • Science of Sound • Brightstorm - Sound

8. Check Your Understanding • Read The Nature of Sound (Moodle) • Complete the graphic organizer in your notebook • Answer questions 1 to 16in your notebook • Explain (give details) how 3 factors affect the speed of sound. What do you have to do to the medium to make sound travel fastest? Main Idea Sound waves interact… detail detail detail

9. Questions of the Week • If all sounds are caused by vibrations, why aren´t all sounds exactly the same? • Why are some sounds louder than others?(What factors affect the loudness of a sound?) • Why are some sounds high pitched, like a flute, and some sounds are low pitched, like a tuba?(What does the pitch of a sound depend on?)

10. Properties of Sound • If all sounds are caused by vibrations, why aren´t all sounds exactly the same? Because not all vibrations are the same! • There are 4 main properties of sound that we use to distinguish one sound wave from another: • Intensity, loudness, frequency, and pitch

11. Properties of Sound • Intensity is the amount of energy the wave carries per second through a unit of area (eg. watts/m2) • eg. A shout carries more energy than a whisper. • Loudness (amplitude) describes what you actually hear.  Is measured in decibels (dB) • A wave of greater intensity sounds louder. • Sound waves of high amplitude have more intensity because they carry more energy per second. • The farther away a sound wave is from its source, the quieter the sound. • The higher the decibel rating of a sound, the louder the sound is

12. Frequency is the number of waves per second (measured in Hz) In humans, stretched vocal cords vibrate faster and produce a higher frequency. Bass 80-260 Hz Soprano over 1,000 Hz Ultrasound - above normal Infrasound - below normal Several animals (eg. bats, dolphins, whales, and some insects), use ultrasound or infrasound to identify their prey (or to avoid being caught!) Properties of Sound

13. Properties of Sound • Pitch is how high or low a sound seems. It depends on the frequency of the wave, and not the loudness of the sound. • higher frequency = higher pitch • lower frequency = lower pitch • eg. string instruments (guitar/violin) • Tight string, high frequency, high pitch. • A short string produces a higher pitch. • eg. pipe/tube instruments (recorder/organ) • Long tube, low frequency, low pitch • Short tube, high frequency, high pitch

14. The Doppler Effect • Close your eyes. Have you ever experienced this phenomenon? • This is called the Doppler Effect • eg. Police siren, jet plane • As a sound source moves towards the listener, the waves reach the listener with a high frequency; the pitch appears to increase. • As the source moves away, the pitch drops. • Video • This same idea is used in Astronomy to tell if distant galaxies are moving towards or away from us.

15. Check Your Understanding • Read Properties of Sound (Moodle) • Complete the Textbook Survey Graphic Organizer in your notebook for the 5 facts you came across in the reading. • Answer questions 1 to 16 in your notebook. • Textbook Survey Graphic Organizer: Choose 5 facts. For each of your 5 facts: • Fact: (Write the fact in your own words) • eg.Pitch is how high or low a sound is. • Comment/Reaction/Opinion/Example:(Write a comment, reaction, or opinion to the stated fact) • eg. High pitched sounds have high frequencies, like a flute • Question: (Write a question to yourself that will help you to remember the fact) • eg. How does the pitch of a sound depend on the frequency?

16. Question of the Day • How do we hear sound?

17. How You Hear – The Outer Ear • Hearing is a matter of waves and vibrations • Humans can hear sounds with frequencies between 20 Hz and 20,000 Hz • The ear consists of 3 parts: the outer, middle, and inner ear • These parts must work together for us to hear sound • 1) The outer ear contains the pinna, the ear canal, and ear drum (tympanic membrane) • The pinna collects sound, and with the ear canal sound waves are funneled towards the ear drum. • Sound waves hit the ear drum, causing it to vibrate

18. How You Hear – The Middle Ear • 2) The middle ear is made up of the 3 smallest bones in the body (called ossicles), which are connected to one another: • hammer (malleus) • anvil (incus) • stirrup (stapes) – only 0.25 cm long! • Movement of the ear drum causes the hammer to vibrate • This causes the anvil and stirrup to also vibrate • Vibration of the stirrup causes vibrations in the fluid-filled inner ear.

19. How You Hear – The Inner Ear • 3) The inner ear is made up of the spiral-shaped cochlea (filled with liquid) • Contains over 10,000 nerve cells that have hair-like structures (called haircells). • The vibrating stirrup causes the fluid in the cochlea to vibrate. • Low frequency sounds (eg. 20 Hz) are sensed at the end of the cochlea, while high frequency sounds (20,000 Hz) are sensed at the beginning of the cochlea • Hair cells pickup these vibrations and send messages to the auditory cortex in the temporal lobe of the brain, where the sound is interpreted.

20. How You Hear • BrainPop - Hearing • Video #1 • Video #2

21. Hearing Loss • May lose hearing due to injury, infection or aging. • Injury can cause the tiny bones to disconnect, surgery can sometimes fix it. • Punctured ear drums or viral or bacterial infection can also cause damage. • Extended exposure to loud sounds can damage the tiny hairs. Wear ear protection! • As you age the tiny hair cells become less effective at detecting signals, especially at high frequency • Hearing aids may help to restore hearing. • Prolonged exposure to noises above 85 dB can cause hearing loss.

22. Check Your Understanding • Read How You Hear Sound (Moodle) • Make a flowchart that shows how you hear sound. • Answer questions 1 to 13 in your notebook. • Complete the 3 Whats? graphic organizerforthe reading. • Write a short paragraph answering the following question: • How might your life be different if you were not able to hear sound? • 3 Whats? Graphic Organizer: In complete sentences, write the following: • What? (What 3 things did I learn from this section?) • SoWhat? (What difference does it make that I know this? Why is this important/relevant/ useful to me?) • NowWhat?(Follow up! How do I use this information to make a difference in what I know or can do? How does this relate to the Unit’s outcomes?)

23. Question of the Day • How do we use sound in our daily lives?

24. Applications of Sound • When sound hits an obstacle or barrier, it gets reflected back • Sonar is a system for navigation and detecting reflected sounds. • High frequency ultrasound travels through water. • When it hits something it bounces back. • To calculate distance, measure the time it takes to get there and back and divide by 2 • The intensity of the reflected wave tells the size and shape.

25. Applications of Sound • Many animals use ultrasound and infrasound to communicate and to navigate • Ultrasound whistles for dogs: over 20,000 Hz. • Infrasound communication for elephants: under 20 Hz. • Echolocation uses sound to determine distances • eg. dolphins and whales • Some fish (180,000 Hz) and bats (100,000Hz) navigate and find food

26. Ultrasound • Doctors use ultrasound to see inside the body to help diagnose and treat patients. • Fetal exam -4M Hz. • Focused waves can be used to painlessly destroy unwanted tissue. • Uses at home: tooth brush, jewelry cleaners and autofocus on cameras.

27. Check Your Understanding • Read Applications of Sound • Answer Questions 1 to 11 in your Journals • 3-2-1Write in your Journals three things you learned, two questions you have, and one thing you liked about today’s class

28. Resources • Google.ca • Wikipedia • http://www.physicsclassroom.com • YouTube.com • Brainpop.com