1. Conceptual Physics Notes on Chapter 25 Sound

2. Sound   All sounds are produced by the vibrations of material objects.   Pitch describes our impressions about frequency or sound when produced by vibrations.

3. Sound   A “normal” person can distinguish sound frequencies between 20 and 20,000 hertz. below 20 hertz is known as infrasonic.below 20 hertz is known as infrasonic. above 20,000 hertz is known as ultrasonic.above 20,000 hertz is known as ultrasonic. NOTE: No human can hear above or below 20 - 20000 hertz.

4. Sound   When something vibrates, it causes a wave that compresses and stretches.   In physics we call this Compression and Rarefaction.

5. Sound  Sound needs a medium to travel through. But sound travels at different speeds in different mediums. Air --- can range from 330 m/s - 350 m/s Air --- can range from 330 m/s - 350 m/s NOTE: For ALL problems we will take the average speed of 340 m/sNOTE: For ALL problems we will take the average speed of 340 m/s Liquid - can range from 1325 m/s - 1375 m/s Liquid - can range from 1325 m/s - 1375 m/s NOTE: For water we will take the average speed of 1360 m/s (Water)NOTE: For water we will take the average speed of 1360 m/s (Water) Solid - Can range from 4500 m/s - 6000 m/s Solid - Can range from 4500 m/s - 6000 m/s NOTE: For solids we will take the average speed of 5100 m/s (Steel)NOTE: For solids we will take the average speed of 5100 m/s (Steel)

6. Sound LOUDNESS   Loudness is subjective. Each person hears sound different due to each persons brain interrupts sound different.   Loudness is measured in Decibel (dB). Decibels are based on a logarithmic variation.   EX: 40 dB is 100 times as loud as 20 dB 100 dB is 10 times as loud as 90 dB See Table 26.1 Pg. 394

7. Sound  Forced vibration is when a vibrating object causes a object in contact with it to also vibrate.

8. Sound  Interference of sound waves affects the loudness of sounds.

9. Sound  Different objects create different sound waves.

10. Sound  Sound waves can produce HARMONICS.

11. Sound  Harmonics can be easily demonstrated with a tuning fork and tube.

12. Sound BEATS  Beats happen when two waves interfere with each other in a way that some of the wave energy overlaps constructively and some overlap destructively.

13. Sound If you subtract the frequencies of the two tuning forks, you can get the beat frequency. If you subtract the frequencies of the two tuning forks, you can get the beat frequency. EX: 262 Hz and 266 HzEX: 262 Hz and 266 Hz 262 Hz and 272 Hz 262 Hz and 272 Hz