1. Sound Waves Chapter 16

2. Old Riddle If a tree falls in the middle of a forest and no one is around, does it make a sound? If a tree falls in the middle of a forest and no one is around, does it make a sound?

3. Answer To a scientist, the tree does make a sound no matter whether someone hears it or not. To a scientist, the tree does make a sound no matter whether someone hears it or not. Sound- disturbance that travels through a medium as a longitudinal wave Sound- disturbance that travels through a medium as a longitudinal wave

4. Sound Wave

5. Sound Waves Sound Waves reflect, diffract through narrow openings and around barriers, and interfere with each other Sound Waves reflect, diffract through narrow openings and around barriers, and interfere with each other Reflection- sounds bounce off surfaces such as walls Reflection- sounds bounce off surfaces such as walls A reflected sound wave is called an echo A reflected sound wave is called an echo

6. Defraction Why can you hear someone in a classroom before you enter the room? Why can you hear someone in a classroom before you enter the room? Sound waves do not travel in straight line Sound waves do not travel in straight line They expand and contract to fill the room which they are entering They expand and contract to fill the room which they are entering

7. Interference Interference- when waves interact with each other Interference- when waves interact with each other Constructive Constructive Destructive Destructive

8. Speed of Sound If a sound wave is traveling through air at room temperature, the speed of the wave is 343 m/s. If a sound wave is traveling through air at room temperature, the speed of the wave is 343 m/s. The speed of sound depends on many factors such as elasticity, density, and temperature of the medium through which it is traveling. The speed of sound depends on many factors such as elasticity, density, and temperature of the medium through which it is traveling. Turn to pg 543. Look at the Math Analyzing Data and do problems 1-3. Turn to pg 543. Look at the Math Analyzing Data and do problems 1-3.

9. Elasticity- ability of a material to bounce back after being disturbed Elasticity- ability of a material to bounce back after being disturbed Which is more elastic? Which is more elastic? Modeling clay Modeling clay Rubber band Rubber band The more elastic a medium, the faster the sound travels. The more elastic a medium, the faster the sound travels. Solid- more elastic Solid- more elastic Liquid- middle elastic Liquid- middle elastic Gas- Least elastic Gas- Least elastic Elasticity

10. Density- how much matter that is in an object Density- how much matter that is in an object In an object with the same state (solid, liquid, gas), sound travels slower in denser object. In an object with the same state (solid, liquid, gas), sound travels slower in denser object. Why? Why? The particles do not move as quickly in denser object The particles do not move as quickly in denser object Density

11. Temperature- how quickly particles move Temperature- how quickly particles move Sound travels more slowly in lower temperatures Sound travels more slowly in lower temperatures Which wins? Put in order from fastest to slowest. Which wins? Put in order from fastest to slowest. 30º C 30º C 20º C 20º C 10º C 10º C 0º C 0º C Temperature

12. Loudness- perception of energy of a sound Loudness- perception of energy of a sound Loudness depends on two things: the amount of energy it takes to make the sound and the distance from the source of the sound Loudness depends on two things: the amount of energy it takes to make the sound and the distance from the source of the sound Shouting vs. whispering Shouting vs. whispering The closer to a sound you are, the louder The closer to a sound you are, the louder Loudness

13. The greater the energy used to make the sound, the louder the sound. The greater the energy used to make the sound, the louder the sound. Guitar String- more energy used to pick the string up, the louder it is. Guitar String- more energy used to pick the string up, the louder it is. The more energy that is used, the higher the amplitude. The more energy that is used, the higher the amplitude.

14. Loudness increases as you get closer to the origination of the sound. Loudness increases as you get closer to the origination of the sound. Why? Why? The closer you are to the origination of the sound, the smaller the wave and the more energy you hear. The closer you are to the origination of the sound, the smaller the wave and the more energy you hear. As a sound wave travels, the waves spread and energy is also spread out. As a sound wave travels, the waves spread and energy is also spread out.

15. Intensity Intensity- the amount of energy a sound waves carries per second through a unit area Intensity- the amount of energy a sound waves carries per second through a unit area A sound wave with a greater intensity, sounds louder. A sound wave with a greater intensity, sounds louder. As you walk away, it gets softer and intensity goes down. As you walk away, it gets softer and intensity goes down.

16. Loudness is measured in decibels (dB) Loudness is measured in decibels (dB) Loudness of what we can barely hear is 0dB Loudness of what we can barely hear is 0dB 30 dB is 3 times the level of 10 dB 30 dB is 3 times the level of 10 dB Sounds louder than 100 dB can damage your ears Sounds louder than 100 dB can damage your ears Decibels

17. Pitch- of a sound is a description of how low or how high the sound seems to a person Pitch- of a sound is a description of how low or how high the sound seems to a person Sound waves with a high frequency has a high pitch. Sound waves with a high frequency has a high pitch. Sound waves with a low frequency has a low pitch. Sound waves with a low frequency has a low pitch. Pitch

18. Female Female (alto) (alto) Male Male (bass) (bass)

19. We can hear frequencies between 20 Hz and 2000 Hz We can hear frequencies between 20 Hz and 2000 Hz Ultrasound- sound waves above the normal hearing range Ultrasound- sound waves above the normal hearing range Ultra-beyond Ultra-beyond Infrasound- sound waves below the normal human range of hearing Infrasound- sound waves below the normal human range of hearing Infra- below Infra- below

20. When singing, you change pitch often. When singing, you change pitch often. When you change pitch, you use your vocal cords. When you change pitch, you use your vocal cords. Nestled in your vocal cords is your voice box, which is called a larynx Nestled in your vocal cords is your voice box, which is called a larynx To sing, you contract and relax muscles in your throat and vocal cords To sing, you contract and relax muscles in your throat and vocal cords

21. The Doppler Effect- the change in frequency of a wave as its source moves in relation to an observer The Doppler Effect- the change in frequency of a wave as its source moves in relation to an observer The sound waves are a change frequency which changes the pitch The sound waves are a change frequency which changes the pitch When a sound source moves, the frequency of waves changes because the motion of the source adds to the motion of the waves When a sound source moves, the frequency of waves changes because the motion of the source adds to the motion of the waves Ex. Tennis ball and wall- further you move back the less the frequency Ex. Tennis ball and wall- further you move back the less the frequency Doppler Effect

24. Groups of Instruments Stringed- guitar and violin Stringed- guitar and violin Vibration when a string is strummed or plucked Vibration when a string is strummed or plucked Pitch depends on length, thickness, material, and how tightly its stretched Pitch depends on length, thickness, material, and how tightly its stretched Wind- brass and woodwind Wind- brass and woodwind Vibrations against mouthpiece or reed Vibrations against mouthpiece or reed Pitch depends on air column length Pitch depends on air column length Percussion- drums, cymbals, and xylophones Percussion- drums, cymbals, and xylophones Vibrate when struck Vibrate when struck Pitch depends on size, materials, and tension on drumhead Pitch depends on size, materials, and tension on drumhead

25. Human Ear Function of your ear is to gather sound waves and send sound to your brain. Function of your ear is to gather sound waves and send sound to your brain. The outer ear funnels sound waves, the middle ear transmits the waves inward, and the inner ear converts sound waves into a form that travels to your brain The outer ear funnels sound waves, the middle ear transmits the waves inward, and the inner ear converts sound waves into a form that travels to your brain

26. Outer Ear Outermost ear looks and acts like a funnel Outermost ear looks and acts like a funnel Ear canal- narrow region leading from the outside of the human ear to the eardrum Ear canal- narrow region leading from the outside of the human ear to the eardrum Eardrum- small, tightly stretched, drumlike membrane that vibrates when sound enters Eardrum- small, tightly stretched, drumlike membrane that vibrates when sound enters

27. Middle Ear Behind the eardrum, is the middle ear. Behind the eardrum, is the middle ear. Three smallest bones in your body make up the middle ear: hammer, anvil, and the stirrup Three smallest bones in your body make up the middle ear: hammer, anvil, and the stirrup Eardrum causes the hammer to vibrate Eardrum causes the hammer to vibrate Hammer causes the anvil to vibrate Hammer causes the anvil to vibrate Anvil causes the stirrup to vibrate Anvil causes the stirrup to vibrate

28. Inner Ear The stirrup’s vibrations transfer to the cochlea The stirrup’s vibrations transfer to the cochlea Cochlea- fluid filled sac shaped like a snail shell Cochlea- fluid filled sac shaped like a snail shell On the cochlea are several hairs that sense the vibrations and send the messages to the brain through the auditory nerve On the cochlea are several hairs that sense the vibrations and send the messages to the brain through the auditory nerve

30. Echolocation Echolocation- use of Echolocation- use of reflected sound to determine distances or to locate objects Animals use echolocation to find food and avoid predators Animals use echolocation to find food and avoid predators Bats Bats Frequency around 100,000 Hz Frequency around 100,000 Hz Dolphins Porpoises and Whales Dolphins Porpoises and Whales Frequencies around 150,000 Frequencies around 150,000

31. Ultrasound Ultrasound technologies such as sonar and ultrasound images are used to observe things that cannot be seen directly Ultrasound technologies such as sonar and ultrasound images are used to observe things that cannot be seen directly Sonar-Sound Navigation and Ranging Sonar-Sound Navigation and Ranging Used to determine depth of water, map the ocean floor, and locate sunken ships Used to determine depth of water, map the ocean floor, and locate sunken ships Total distance divided by two Total distance divided by two

33. Ultrasound Sonogram- use of reflected ultrasound waves to create a picture Sonogram- use of reflected ultrasound waves to create a picture See how many babies there are See how many babies there are See sex of baby See sex of baby Position of a baby Position of a baby Diagnose and treat medical conditions Diagnose and treat medical conditions