2. Riddle Me This!!!

3. Riddle
If a tree falls in a forest and no one hears it, does the tree make a sound?
To answer the riddle, you must decide what the word “sound” means. If sound is something that a person must hear, then the tree makes no sound. If sound can happen whether a person hears it or not, then the tree makes a sound. 3

4. Riddle
To a scientist, a falling tree makes a sound whether someone hears it or not.
When a tree crashes down, the energy with which it strikes the ground causes a disturbance.
Particles in the ground and the air begin to vibrate, or move back and forth. The vibrations create a sound wave as the energy travels through the two mediums. 4

5. a range of compression wave frequencies to which the
SOUND
a range of compression wave
frequencies to which the
human ear is sensitive

6. What is sound?
Sound is a compressional wave which travels through the air through a series of compressions and rarefactions.

7. Sound Waves
- The Nature of Sound
Sound is a disturbance that travels through a medium as a longitudinal wave. As a gong vibrates, it creates sound waves that travel through the air.
Get it on
Bang a Gong

8. Drawing with Sound

9. Sound Waves What are sound waves made of?
- The Nature of Sound
Sound Waves
What are sound waves made of?
Sound is transmitted through the vibrations and collisions of the particles.
Sound waves travel in all directions away from their source.

10. Sound Waves Air or other matter does not travel with the sound waves.
If air did travel with sound, wind gusts from music speakers would blow you over at a dance.
Sound waves require a Medium.
What is a medium again?
Sound waves travel through water, glass, and metal.

11. The Human Ear
Your ears change sound waves into electrical signals that allow you to hear.

12. The Human Ear
The outer ear funnels sound waves, the middle ear transmits the waves inward, small organs increase the size of the vibrations, and the inner ear transforms sound waves into a form that travels to your brain.

13. Outer Ear
The first section of your ear is the outer ear. The outermost part of your outer ear looks and acts like a funnel. It collects sound waves and directs them into a narrow region called the ear canal. Your ear canal is a few centimeters long and ends at the eardrum. The eardrum is a small, tightly stretched, drum like membrane. The sound waves make your eardrum vibrate, just as a drum vibrates when you strike it.

14. Middle Ear
Behind the eardrum is the middle ear. The middle ear contains the three smallest bones in your body—the hammer, the anvil, and the stirrup. The hammer is attached to the eardrum, so when the eardrum vibrates, the hammer does too. The hammer then transmits vibrations first to the anvil and then to the stirrup.

15. Inner Ear
A membrane separates the middle ear from the inner ear, the third section of the ear. When the stirrup vibrates against this membrane, the vibrations pass into the cochlea.
The cochlea (KAHK lee uh) is a fluid-filled cavity shaped like a snail shell.

16. Hearing Loss and Deafness
Many parts of the ear must work together for you to hear sounds.
If any part of the ear is damaged or does not work properly, hearing loss or deafness may result.

17. Hearing Loss
When hearing loss occurs, a person may have difficulty hearing soft sounds or high-pitched sounds.
Tinnitus: results from long-term exposure to loud sounds.
People with this cannot differentiate between words that sound the same.

18. Hearing Loss
Hearing loss can occur suddenly if the eardrum is damaged or punctured. (Imagine trying to play a torn drum!) For this reason, it is dangerous to put objects into your ear, even to clean it. Infections also can damage the delicate inner ear, causing permanent hearing loss.

19. Protecting your Hearing
Short exposure to sounds that are loud enough to be painful can cause hearing loss.
Earplugs
Lower the volume
Move away from loud sounds

20. The outer ear funnels sound waves into the ear canal.
- How You Hear Sound
How You Hear Sound
The outer ear funnels sound waves into the ear canal.
Sound waves make the eardrum vibrate.
Tiny bones in the middle ear transmit vibrations to the inner ear.
Vibrations in the cochlea of the inner ear send messages to the brain. 20

21. Properties of Sound

22. Interesting Fact
In some western movies, a character would be shown putting an ear to the hard ground to find out if someone was coming. This technique actually works because sound travels faster and with less loss of energy through the ground than through air.

23. The Speed of Sound X-1 airplane Chuck Yeager 1947 293 m/s
- The Nature of Sound
The Speed of Sound
X-1 airplane
Chuck Yeager
1947
293 m/s
(480 miles/sec)
12,000 meters above sea level
Speed of sound at that altitude is 290 m/s

24. The Speed of Sound
Speed of sound depends only on the medium in which the sound is traveling.
Sound travels quickly through air, but it travels faster in liquids, and even faster in solids.
Example:
You are at the pool and one kid is humming while another kid is yelling. You hear them at the same time even if one person is yelling louder.

25. The Speed of Sound
WATCH SONIC BOOM!!! 25

26. The speed of sound depends on…
- The Nature of Sound
The Speed of Sound
The speed of sound depends on…
the elasticity
the density
the temperature
This chart is important!

27. How does temperature affect the speed of sound? Why?
Temperature is also a condition that affects the speed of sound. Heat, like sound, is a form of kinetic energy. Molecules at higher temperatures have more energy, thus they can vibrate faster. Since the molecules vibrate faster, sound waves can travel more quickly.

28. Elasticity
Elasticity is the ability of a material to bounce back after being disturbed. You can model elasticity by representing the particles in a medium as being held together by springs.

29. Elasticity The more elastic a medium, the faster sound travels in it.
Sounds can travel well in solids, which are usually more elastic than liquids or gases.

30. Density
Density is how much mass there is in a given volume. The volumes of the cubes are the same, but the brass has more mass.

31. Density
In materials in the same state of matter (solid, liquid, or gas)
Sound travels more slowly in denser mediums.

32. How do you describe sound?
Describing Sound
How do you describe sound?

33. Mike Thompkins
Clarity
Mash-up
Dynamite
Only Girl

34. Pitch and Frequency How low or high a sound seems to be is the pitch.
Frequency is the….
How is frequency expressed?
How is pitch and frequency related?
Lowest note on a piano is 40 Hz while the screech of a bat is 10,000 Hz or higher.

35. How is frequency related to pitch?
The pitch of a sound wave is directly related to frequency. A high-pitched sound has a high frequency (a screaming girl). A low-pitched sound has a low frequency (a fog-horn).
A healthy human ear can hear frequencies in the range of 20 Hz to 20,000 Hz. Humans cannot hear below 20 Hz. Sounds below this frequency are termed infrasonic.
Sounds above 20,000 Hz are termed ultrasonic. Some animals, such as dogs, can hear frequencies in this range in which humans cannot hear.

36. Using Sound
Ultrasonic: sound waves with frequencies above the normal human range of hearing.
Question: Have you ever noticed how dogs can hear much higher pitches than humans?

37. Frequencies Heard by Different Animals
Frequency Range (Hz)
Bat
2,000 to 110,000
Porpoise
75 to 150,000
Cat
45 to 64,000
Beluga Whale
1,000 to 123,000
Elephant
16 to 12,000
Human
20 to 20,000
Dog
67 to 45,000

38. Mosquito
Frequencies

39. What is the Doppler Effect?
The Doppler Effect is the apparent change in frequency detected when the sound is moving relative to the hearer.

40. Loudness is a measure of how well a sound can be heard.

41. Increasing Amplitude
If you strike the tuning fork harder, you increase the amplitude.
Amplitude: the largest distance the particles in a wave vibrate from their rest position.
The larger the amplitude the louder the sound.
Amplifier: receives sound signals in the form of electric current
The amplifier then increases the energy and makes the sound louder.

42. Loud Music Interesting Fact
Listening to loud music and attending loud concerts can be harmful to your hearing. Loudness is expressed in decibels (dB). Long-term exposure to sounds above 85 dB is considered hazardous to your hearing. Sounds louder than 85 dB take less time to cause hearing damage. Music concerts are often 110 dB or louder, so the potential for hearing damage is very real.

43. Measuring Loudness We use decibel to express loudness.
Any sound 120 dB or higher is painful.

44. Decibel Levels of Common Sound
The softest sound you can hear 20
Whisper 25
Purring cat 60
Normal conversation 80
Lawn mower, vacuum cleaner, truck traffic
100
Chain saw, snowmobile
115
Sandblaster, loud rock concert, automobile horn
120
Threshold of pain
140
Jet engine 30 m away
200
Rocket engine 50 m away

45. extends from approximately
The audio spectrum
extends from approximately
20 Hz to 20,000 Hz.

46. Range of Some Common Sounds

47. The human ear relates
amplitude to
loudness
and
frequency to
pitch.

48. * Fact * Resonance - the inducing All objects have a natural
frequency of vibration.
Resonance - the inducing
of vibrations of a natural
rate by a vibrating source
having the same frequency
Car commercial will break glass
“sympathetic vibrations”

49. Famous Bridge Collapses: Evidences of Resonance?
Tacoma Narrows link
Others link

50. SUMMARY:
Sound travels through different media.
We hear sound which usually travels through air. Sound travels through other media as well, such as water and various solids.
Sound travels different speeds in different media. Sound typically travels faster in a solid that a liquid and faster in a liquid than a gas.
Lower density=faster speed of sound
The higher the temperature, the faster the particles of the medium will move and the faster the particles will carry the sound.

51. What is sound intensity?
Sound intensity is the energy that the sound wave possesses. The greater the intensity of sound the farther the sound will travel and the louder the sound will appear.
Loudness is very closely related to intensity. Loudness is the human perception of the sound intensity. The unit for loudness is decibels.

52. What is echolocation?

54. Watch Echolocation video 

55. What is sonar?
Sonar is a system that uses the reflection of underwater sound waves to detect objects. This has been used to find sunken ships and schools of fish.

56. Ben