1. Sound

2. Doppler Effect
The change in frequency due to the motion of the sound source or the receiver of the sound.
Named after Christian Doppler
Greater speed of sound = greater Doppler Effect

3. You

4. Shock Waves Produced by supersonic aircraft
*Supersonic = faster than speed of sound
Made from overlapping spheres that form a cone and travel until they hit the ground

5. Shock Wave When waves reach the listeners they hear a sonic boom
Due to the waves reaching the listener all at the same time

6. Sound Produced by vibrations Under ordinary circumstances:
frequency of = frequency of
vibrating source sound waves

7. Sound Pitch How we describe the frequency (loudness) of a sound
High Pitch = High Frequency
Low Pitch = Low Frequency

8. Sound Young people can generally hear from 20 to 20,000 Hz
The older you get the more your hearing range shrinks
*Especially the
higher frequency
sounds

9. Sound Infrasonic *Frequency below 20 Hz Ultrasonic
*Frequency above 20,000 Hz
Humans cannot hear these

10. Sound
Compressional Wave

11. Sound in Air
When you clap your hands you produce a pulse of air that travels through the room.

12. Sound in Air
Think of this pulse in terms of a window in an empty room.
When open the door you produce a compression which travels through the empty room to the open window and pushes the curtain outward.
The pulse of compressed air traveled through the room.

13. Sound in Air
When you close the door this pushes air particles out of the room which makes for low pressure in the room. This will make the air outside of the room rush inside and push the curtain inside the room.
Called a rarefaction

14. Media that Transmit Sound
If you put your ear to the ground you will hear the hoofbeats of running horses through the ground sooner than you would through the air.

15. Media that Transmit Sound
Same in water. You will hear something sooner underwater than in the air.

16. Media that Transmit Sound
Sound will travel faster in solids than liquids and faster in liquids than gases

17. Media that Transmit Sound
Sound will not travel through a vacuum (empty space).
Sound will not travel
through space.

18. Speed of Sound
Depends on the elasticity (ability of something to return to its original shape) of the material
FYI: Steel is consider elastic and putty inelastic
*Sound travels fifteen times faster in steel than air

19. Loudness Physiological sensation sensed in the brain
Human perception of sound intensity

20. Loudness
Measured in decibels, dB
After Alexander Graham Bell

21. Loudness Whisper = 20 dB Street Traffic = 70 dB Rock Music = 115 dB
Threshold of pain (humans) = 120 dB
Jet engine = 140 dB

22. Natural Frequency
Objects vibrate at their own specific set of frequencies
Together this produces the object’s unique sound.

23. Natural Frequency Depends on object’s elasticity and shape
Also, this is the frequency that requires the least amount of energy to continue.

24. Resonance
When the forced vibration on an object matches the object’s natural frequency
Increases the amplitude

25. Resonance
Examples:
Opera singers breaking windows

26. Resonance
In 1831 English infantry troops marching across a footbridge caused the bridge to collapse. Their footsteps continued to resonate through the bridge until it collapsed. In 1940 the Tacoma Narrows Bridge collapsed due to wind generated resonance.

27. Tacoma Narrows Bridge

28. Beats
Occurs when two tones of slightly different frequency are sounded together
Periodic variation in the
loudness of sound

29. Parts of Your Ear Outer Gathers sound waves Middle
Amplifies the sound waves
Inner
Converts the sound waves into nerve impulses

30. Parts of Your Ear

31. Middle Ear What are the three tiny bones in your middle ear? Stirrup
Anvil
Hammer

32. Inner Ear
Contains the cochlea: spiral-shaped structure that contains liquid and tiny hair cells
The hair cells in the cochlea begin to vibrate and send nerve impulses through the auditory nerve to the brain.

33. Hear loss
When the tiny hair cells are damaged or destroyed your hearing will become damaged.
New research suggests that these hair cells may be able to repair themselves.

34. In conclusion, if a tree falls in the woods and there is no one around to hear it does it make a sound?