1 / 16

13.2 Sound Intensity and Resonance

13.2 Sound Intensity and Resonance. pp. 487 - 493 Mr. Richter. Agenda. Podcast Check Questions about 13.1 Sound Waves Upcoming Schedule Notes: Intensity and Volume Decibel levels Forced Vibrations and Resonance. Upcoming Schedule. Today 13.2 Intensity and Resonance

zocha
Télécharger la présentation

13.2 Sound Intensity and Resonance

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 13.2 Sound Intensity and Resonance pp. 487 - 493 Mr. Richter

  2. Agenda • Podcast Check • Questions about 13.1 Sound Waves • Upcoming Schedule • Notes: • Intensity and Volume • Decibel levels • Forced Vibrations and Resonance

  3. Upcoming Schedule • Today 13.2 Intensity and Resonance • Tomorrow 13.3 Harmonics • Friday: Wrap Up and Begin Review • Mr. Richter Out Monday and Tuesday • Monday: In class review (on your own) • Tuesday: Ch. 13 Quizam

  4. Objectives: We Will Be Able To… • Calculate the intensity of sound waves. • Relate intensity, decibel level, and perceived loudness. • Explain why resonance occurs.

  5. Sound Intensity

  6. Sound Intensity • Sound intensity is the power of a sound wave for a given area. • It’s how much energy a plane wave carries through an area • Since sound waves are spherical, the area is the surface area of a sphere (4πr2) • Units of intensity: W/m2

  7. Sound Intensity • The intensity of a sound wave decreases with the square of the distance from the source. • The same amount of energy is spread over a larger area.

  8. Decibel Levels

  9. Decibel Levels • Humans interpret the intensity of a sound wave as volume. • The more intense a wave is, the louder it sounds. • However, volume (human perception of intensity) is not directly proportional to intensity. • Humans measure volume (relative intensity) on a logarithmic scale: decibels (dB). • If the intensity is 10 times louder, the decibel level increases by 10 dB. • An increase in 10 dB is perceived to be approximately twice as loud.

  10. Decibel Levels • A vacuum cleaner is has 10 times the intensity of an air conditioner. • Which means it is 10 dB louder. • Which means the vacuum cleaner sounds twice as loud as an air conditioner to us.

  11. Forced Vibrations and Resonance

  12. Forced Vibrations • If a vibrating object is attached to another object, the other object will begin to vibrate as well. • Think of you kicking your legs sitting on a swing. • You vibrate, and the swing will vibrate as well. • This is called forced vibration. The other object vibrates with sympathetic vibrations. • The vibrating object transfers energy to the other objects. • Often this causes a change in intensity (volume).

  13. Resonance • Every object has a natural frequency of vibration. • When the forced vibration (input) is equal to the natural frequency of vibration of the object, the system is said to be in resonance. • Systems in resonance will transfer energy much more quickly from one object to another. • To swing on the swings, you have to kick your feet at the correct intervals. Otherwise, chaos.

  14. Resonance • Resonance is not always a good thing. • Just ask the Tacoma Narrows Bridge.

  15. Wrap-Up: Did we meet our objectives? • Calculate the intensity of sound waves. • Relate intensity, decibel level, and perceived loudness. • Explain why resonance occurs.

  16. Homework • p. 486 #1, 3, 4, 6, 7 • p. 493 #1-5

More Related