1. SOUND An Oral Recitation Lecture

2. What produces sound? Any vibrating source produces sound.

3. What kind of waves are sound waves? Sound waves are mechanical waves. They require a medium to propagate.

4. What type of waves are sound waves? Sound waves are longitudinal waves. They move particles back and forth forming compressions and rarefactions.

5. Speed of Sound Waves The speed of sound waves vary with different mediums Solids  fastest Liquids  faster Gases  slowest Why?

6. As the temperature increases in the same medium, the sound waves travel faster!

7. What property of sound is related to its frequency? Frequency is directly proportional to the pitch of sound.

8. Human Hearing Audible Range 20 Hz to 20 kHz (20 000 Hz) Ultrasound Very high frequency sound Above audible range Infrasound Very low frequency sound Below audible range

9. What property of sound is related to its amplitude? Amplitude is directly proportional to the loudness of sound.

10. What happens to sound waves when they hit a boundary? Sound waves are reflected when they hit a boundary. Reflection of sound waves is called an ECHO.

11. Speed of Sound Waves The speed of sound waves can be determined using its echo. Sound detector Ears Microphone Displays Sound Waves: Cathode-Ray Oscilloscope

12. Cathode-Ray Oscilloscope a.k.a. CRO

13. Example 1 When the horn of the ship is sounded, the passengers hear an echo from a cliff after 4.0 s. If the speed of sound is 340 m/s, how far away is the cliff?

14. Example 2 A boy is stranded on an island. He shouts for help but all he can hear in reply is the echo of his shout from the cliff 500 m away. If the speed of sound is 340 m/s, what is the time interval between the boy shouting and hearing the echo?