1. ~ Sound ~ The Nature of Sound  Speed of Sound  Human hearing  Doppler effect  “Seeing” with sound

2. Speed of Sound 344 m/s in air at 20°C Depends on: Type of medium travels better through liquids and solids can’t travel through a vacuum Temperature of medium travels faster at higher temps

3. Human Hearing sound wave vibrates ear drum amplified by bones converted to nerve impulses in cochlea

4. Human Hearing Pitch highness or lowness of a sound depends on frequency of sound wave human range: 20 - 20,000 Hz ultrasonic waves subsonic waves

5. Human Hearing Intensity volume of sound depends on energy (amplitude) of sound wave measured in decibels (dB)

6. Human Hearing 70 80 100 110 120 40 18 10 0 DECIBEL SCALE

7. Doppler Effect change in wave frequency caused by a moving wave source moving toward you - pitch sounds higher moving away from you - pitch sounds lower

8. “Seeing” with Sound Ultrasonic waves - above 20,000 Hz Medical Imaging SONAR “Sound Navigation Ranging”

9. Sound Problems v s = D ÷ T where v s = speed of sound 344 m/s D = distance in m T = time in s  v s = f x λ, just like a wave problem!

10. Ex #1: Find the wavelength of a 200 Hz sound. GIVEN: v s = 344 m/s f = 200 Hz λ = ? WORK: v s = f x λ λ = v s ÷ f λ = 344 m/s ÷ 200 Hz λ = 1.7 m

11. Ex #2: If you hear a sound 3 s after you see the motion, how far away is it? GIVEN: v s = 344 m/s T = 3 s D = ? WORK: v s = D ÷ T D = v s x T D = 344 m/s x 3 s D = 1032 m

12. ~ Music ` Music vs. Noise Resonance Harmonics Interference Acoustics

13. ~ Music vs. Noise ` Music specific pitches and sound quality regular pattern Noise no definite pitch no set pattern

14. = Resonance = Forced Vibration when one vibrating object forces another object to vibrate at the same frequency results in a louder sound because a greater surface area is vibrating used in guitars, pianos, etc.

15. = Resonance = Resonance special case of forced vibration object is induced to vibrate at its natural frequency

16. = Resonance = “Galloping Gertie” The Tacoma Narrows Bridge Disaster Wind through a narrow waterway caused the bridge to vibrate until it reached its natural frequency.

17. } Harmonics } Fundamental the lowest natural frequency of an object Overtones multiples of the fundamental frequency

18. Constructive - louder | Interference | Interference the ability of 2 or more waves to combine to form a new wave Destructive - softer

19. = Resonance = Beats variations in sound intensity produced by 2 slightly different frequencies both constructive and destructive interference occur

20. _ Acoustics _ Acoustics the study of sound Reverberation echo effect produced by the reflection of sound Anechoic chamber - designed to eliminate reverberation.