1. Sound AP Physics Chapter 12

2. 12.1 Characteristics of Sound Vibration and Waves

3. 12.1 Characteristic of Sound Sound is a longitudinal wave Caused by the vibration of a medium The speed of sound depends on the medium it is in, and the temperature For air, it is calculated as 12.1

4. 12.1 Characteristic of Sound Loudness – sensation of intensity Pitch – sensation of frequency Range of human hearing – 20Hz to 20,000 Hz ultrasonic – higher than human hearing dogs hear to 50,000 Hz, bats to 100,000 Hz infrasonic – lower than human hearing 12.1

5. 12.1 Characteristic of Sound Often called pressure waves Vibration produces areas of higher pressure These changes in pressure are recorded by the ear drum 12.1

6. 12.2 Intensity of Sound: Decibels Vibration and Waves

7. 12.2 Intensity of Sound: Decibels Loudness – sensation Relative to surrounding and intensity Intensity – power per unit area Humans can detect intensities as low as 10 -12 W/m 2 The threshold of pain is 1 W/m 2 12.2

8. 12.2 Intensity of Sound: Decibels Sound intensity is usually measured in decibels (dB) Sound level is given as I – intensity of the sound I 0 – threshold of hearing (10 -12 W/m 2 )  – sound level in dB Some common relative intensities 12.2 Source of SoundSound Level (dB) Jet Plane at 30 m140 Threshold of Pain120 Loud Rock Concert120 Siren at 30 m100 Auto Interior at 90 km/h75 Busy Street Traffic70 Conversation at 0.50 m65 Quiet Radio40 Whisper20 Rustle of Leaves10 Threshold of Hearing0

9. 12.3 The Ear Vibration and Waves

10. 12.3 The Ear Steps in sound transmission 12.3

11. 12.4 Sources of Sound: Strings and Air Columns Vibration and Waves

12. 12.4 Sources of Sound: Strings and Air Columns Vibrations in strings Fundamental frequency Next Harmonic 12.4

13. 12.4 Sources of Sound: Strings and Air Columns Vibrations in strings Next Harmonic Strings produce all harmonics – all whole number multiples of the fundamental frequency 12.4

14. 12.4 Sources of Sound: Strings and Air Columns Vibrations in an open ended tube (both ends) Fundamental frequency Next Harmonic 12.4

15. 12.4 Sources of Sound: Strings and Air Columns Vibrations in open ended tubes Next Harmonic Open ended tubes produce all harmonics – all whole number multiples of the fundamental frequency 12.4

16. 12.4 Sources of Sound: Strings and Air Columns Vibrations in an closed end tube (one end) Fundamental frequency Next Harmonic 12.4

17. 12.4 Sources of Sound: Strings and Air Columns Vibrations in open ended tubes Next Harmonic Closed end tubes produce only odd harmonics 12.4

18. 12.6 Interference of Sound Waves; Beats Vibration and Waves

19. 12.6 Inteference of Sound Waves; Beats If waves are produced by two identical sources A pattern of constructive and destructive interference forms 12.6 Applet

20. 12.7 The Doppler Effect Vibration and Waves

21. 12.7 The Doppler Effect 12.7