1. We are starting with our QUIZ!
Warm-Up 11/19/13
We are starting with our QUIZ!

2. The Nature and Properties of Sound

3. Sound In General Created by something that vibrates
Travels as a compressional wave through a medium (solid, liquid, or gas)

4. 1. The Speed of Sound Depends on the medium
Fastest in solids, slowest in gases
Sound waves travel faster when molecules are closer together!

5. Cont…
Temperature also affects speed: higher temperatures mean higher speeds as the molecules move faster
Speed does NOT depend on how loud the sound is
Air Temperature (degrees C)
Speed of Sound (m/s)
331 20
343

6. 2. Loudness and Intensity
Loudness=the human perception of intensity
Louder waves carry more energy
Remember: energy depends on amplitude (how dense the compressions are)
Sound
Loudness (dB)
Purring cat 25
Vacuum 75
Chain Saw
115
Jet Plane Lift Off
150

7. Cont…
Intensity= the amount of energy that flows from a certain area in a specific amount of time
Higher intensity means louder sound

8. Cont… Intensity decreases with distance
Energy (E) in the wave is converted to other forms of E along the way
Low intensity waves lose energy more quickly
Like a bouncing ball!

9. 3. Pitch Pitch= how high or low a sound seems to be
As frequency of a wave increases, so does the pitch!

10. Cont… Humans most sensitive to frequencies from 20 Hz to 20,000Hz
Ultrasonic= frequencies above 20,000Hz (we can’t hear them)
Ex) waves used in medical treatment
Infrasonic= frequencies below 20 Hz (also can’t hear them)
Ex) Earthquakes

11. 4. The Doppler Effect
Due to changes in pitch or frequency with a moving wave source
Occurs whether it is the source or observer moving

12. Cont… Pitch/frequency increases as source moves toward observer
Decreases as it moves away

13. Your Job! Sound Idea Rake worksheet (we are starting this together!)
Everyone doing Unit 4 Retake Tomorrow
TEST ON FRIDAY