1. Sound

2. Old Riddle:
If a tree falls in a forest and no one is there to hear it, does the tree make sound?
What do you think?

3. How Sound Travels Through a medium Most common…air
Sound: disturbance that travels through a medium in the form of a wave.
Must have vibrations to have sound.

4. How sounds are made
Drum: surface begins to vibrate and creates a disturbance in the molecules. Molecules collide until they get to your ear
Guitar Spring: string vibrates back and forth. Waves travel to your ear.
Vocal cords: are like guitar spring. When you speak you force air through your voice box or larynx. Cords vibrate and send out waves to others ears.

6. Sound in solids and liquids
When you knock on a door
Train tracks
Ground to hear traffic
Sound does not travel in space

7. Sound Bends
Just like when water waves hit something it spreads out, sound can spread out
Going through a doorway
Speed of sound depends on elasticity, density, and temperature of the medium

8. Elasticity
Elasticity: ability of a material to bounce back after being disturbed.
Rubber band vs. clay
Sound travels faster in mediums with higher degree of elasticity.

9. Density Density: how much matter there is in a given amount of space.
Depends on how close together particles are
Sounds travels slower in more dense materials

10. Temperature
Sound travels slower at lower temperatures & faster at higher temperatures

12. Intensity
Intensity: the amount of energy the wave carries per second through an area

13. Loudness
Sound waves with a higher amplitude have a greater intensity and more energy.
The greater the intensity the louder the sound is.
Loudness: what you actually hear

14. Frequency
When vocal cords are stretched vibrate more =higher frequency
When vocal cords are relaxed vibrate less = lower frequency
Frequency of sound wave: number of vibrations that occur per second
Ultrasound: frequencies above the normal human hearing range
Infrasound: frequencies below normal human hearing range.

16. Pitch
Pitch: how high or low the sounds seems. Depends on frequency of sound wave
Tighter string=higher frequency=higher pitch
Short string=higher pitch
Glass with more water= lower pitch
Less Water= higher pitch