2. SOUND WAVES

3. Sound Waves A sound wave is a wave of alternating high-pressure and low-pressure regions of air.

4. How are Sounds Made? When someone or something makes a sound, the air molecules around it vibrate, or move back and forth, and they push into the molecules in front of them. This starts a chain reaction.

5. Can there be sound in outer space?

6. Your Turn

7. Factors that Affect the Speed of Sound Speed of sound depends on: 1. Elasticity = ability to bounce back Faster if more elastic Solids are more elastic than liquids or gases so sound travels fastest through solids 2. Density For materials in the same state of matter Slower in more dense objects- particles do not move as fast because there is more matter in a given area 3. Temperature Slower in lower temperatures (sluggish) Faster in higher temperatures

8. Doppler Effect is the apparent change in the frequency of a sound caused by the motion of either the listener or the source of the sound. Captain Chuck Yeager

9. SupersonicSupersonic Flight Supersonic

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12. Doppler Effect the change in the frequency of a sound caused by motion

14. II. Properties of Sound

15. Speed of Sound Medium velocity m/sec air (20 C) 343 air (0 C) 331 water (25 C) 1493 sea water 1533 diamond12000 iron 5130 copper 3560 glass 5640

16. Loudness= Amplitude How loud or soft Measured in decibels (dB) Low amplitude= soft High amplitude= loud Pitch= Frequency How high or low Measured in Hertz low frequency = low pitch, ex. rumble of a big truck high frequency = high pitch, ex. whistle or siren Fun Fact: women have higher frequencies than men.

17. Loudness of Sound in Decibels SoundLoudness (dbs)Hearing Damage Average Home 40-50 Loud Music 90-100 After long exposure Rock Concert 115-120 Progressive Jet Engine 120-170 Pain

18. Humans can hear from 20 Hz to 20,000 Hz Ultrasound - sound waves with frequencies above the normal human range of hearing. Sounds in the range from 20-100kHz Infrasound - sounds with frequencies below the normal human range of hearing. Sounds in the 20-200 Hz range Pitch= Frequency

19. Resonance the frequency of sound waves exactly matches the natural frequency of an object. http://www.youtube.com/watch?v=O9FrMkhQoA4&feature=related http://www.youtube.com/watch?v=oXV45t6wlWU

20. How we hear a. Outer ear collects sound. b. Middle ear amplifies sound. c. Inner ear converts sound.

21. Musical sound a. Noise has no pattern. b. Music has a pattern and deliberate pitches. c. Sound quality describes differences of sounds that have the same pitch and loudness. d. Every instrument has its own set of overtones.