1. Sound Advice Sound travels in longitudinal waves consisting of vibrating compressions and rarefactions through the air. Sound comes from molecules bumping into each other (vibrating).

2. Speed of Sound Sound travels at 340 m/s in air at 20°C. Although it can vary based on the medium, wind, temperature etc. Sound moves faster in warm air than cold air.

3. Sound also moves faster in liquids and solids versus air. Why might this be? Answer Card Question! A.The molecules in liquids and solids are closer together. B.The molecules in liquids and solids are further apart. C.Liquids and solids are colder. D.I don’t know.

4. A guitar sounds different than a bass guitar, why? This is from a difference in pitch. So what makes some notes high and some notes low? A.Amplitude B.Frequency C.Wavelength D.More than one of the above

5. Which of these two waves is higher pitched? A B

6. High notes have a high frequency and low notes have a low frequency. These two pitches have the same amplitude. But which is a high pitch? A.Top B.Bottom C.Same pitch D.I don’t know

7. So what is the answer… What are the differences in these two waves? A.Amplitude B.Frequency C.Wavelength D.More than one of the above

8. What makes sound loud or soft? The loudness, or volume of sound comes from its amplitude. Which of these two waves is louder? A.Top B.Bottom C.Same volume D.I don’t know

9. Loudness of sound also depends on the intensity of the wave. Intensity is how close you are to the source of the sound. Relative intensity is dependent in a unit called decibels, dB. Decibels are measured in logarithmic units General rule: each unit of 10 dB = 2x increase in sound perception (90 dB is twice as loud as 80 dB. 100 dB is four times louder than 80dB)

10. Which of these is twice as loud as a normal conversation? A.Passenger Car B.747 take off C.Heavy Truck D.Jackhammer

11. Which of these is four times as loud as a jackhammer? A.Rock Band B.747 take off C.Threshold of pain D.Don’t know!

12. Which of these is 8 times as loud as a whisper? A.Quiet living room B.747 take off C.Suburban neighborhood D.Threshold of pain

13. Resonance Resonance occurs whenever successive impulses are applied to a vibrating object in rhythm with its “natural frequency”. Natural Frequency – the frequency in which an object vibrates once it has been set into motion. When the two waves meet in sync with one another it amplifies the sound.

14. Resonance In Music Resonance is important in musical instruments. In an acoustic guitar the guitar resonates with the strings amplifying the sound. Electric guitars do not resonate, so the sound must be amplified electronically.

15. Wind Instruments Wind instruments resonate with the air column inside the instrument.

16. Crazy Resonance In 1940 The Tacoma Bridge in Washington became in resonance with the wind, causing the bridge to oscillate violently and collapse.

17. Resonance also used in: Mufflers Remotes MRI imaging Radios New gall bladder procedure

19. Doppler Effect A shift in frequency and wavelength of waves which results from a source moving in respect to an observer.

20. Doppler Effect Not movingMoving http://www.youtube.com/watch?v=Kg9F5pN5tlI

21. The Sound Barrier Velocities above 340 m/s need to “break” the sound barrier

22. Sound BarrierPast the Sound Barrier http://www.youtube.com/watch?v=gWGLAAYdbbc

23. Sound Term Quiz Explain these terms with words or pictures: 1.Resonance 2.Pitch 3.Natural Frequency 4.Echo 5.Rarefaction 6.Decibel 7.Doppler Effect