Interactive Graded Test on Sound Waves

This is an interactive test that will automatically check your answers and calculate your grade. This test has 30 questions and is based on material from the Sound Waves section of lessons:

• Sound Waves
• Creating Sound Waves
• Detecting Sound Waves
• How Obstacles Affect Sound Waves
• Echoes
• Speed of Sound in a Gas
• Reproducing Sounds
• Making Sounds with Musical Instruments
• Beat Frequencies in Sound
• Noise Reduction
• Active Noise Cancellation

It is a good idea to study these lessons before taking this graded test.

QUIZ

Self-check your understanding

1. Why doesn't sound travel through a vacuum?

   Sound is a waveform in matter, and there is no matter in a vacuumThat is correct.Vacuums absorb most of the soundGood try, but not right. Select another answer.It does travel in space, as verified on Star TrekSorry, not correct. Try another button.

2. How is a sound wave different than a water wave?

   Sound does not travel through waterGood try, but not right. Select another answer.Water waves have a wavelength, while sound waves don'tSorry, not correct. Try another button.A water wave moves up-and-down, while sound is a compression waveThat is correct.

3. What happens when sound hits a thin membrane?

   It causes the membrane to vibrateThat is correct.The membrane reflects most of the soundGood try, but not right. Select another answer.The amplitude of the sound increasesSorry, not correct. Try another button.

4. How does a loudspeaker create sound?

   The speaker cone vibrates back-and-forth, creating compression waves in the airThat is correct.The electricity that powers the speaker makes sounds when it cracklesGood try, but not right. Select another answer.Loudspeakers don't create sound; they detect soundSorry, not correct. Try another button.

5. How do you make sounds from your vocal chords?

   Vocal chords act like tiny loudspeakers, vibrating and forcing sound out your mouthGood try, but not right. Select another answer.Air from your lungs passes over the vibrating vocal chords, making soundThat is correct.It is a myth that your sound comes from vocal chords; it comes from your chestSorry, not correct. Try another button.

6. What happens when you blow across the top of a bottle?

   The top of the bottle gets cold, making a squeaking soundGood try, but not right. Select another answer.Air starts to circulate and vibrate in the bottle, making a soundThat is correct.You must blow into the bottle for anything to happenSorry, not correct. Try another button.

7. What is the purpose of processing the signal created by a detector from a sound wave?

   To make the signal usefulThat is correct.To demonstrate it can be doneGood try, but not right. Select another answer.The sound is processed, not the signalSorry, not correct. Try another button.

8. Why would you cup your ears with your hands when trying to hear faint sounds?

   To focus more sound waves into your earsThat is correct.To make your hands vibrateGood try, but not right. Select another answer.It is a gesture to make people talk louderSorry, not correct. Try another button.

9. Why would less sound be reflected off a rough or porous surface?

   The sound may be reflected multiple times by the porous surfaceThat is correct.Rough surfaces may distort the sound wavesGood try, but not right. Select another answer.Porous materials usually are not very flatSorry, not correct. Try another button.

10. If a material absorbed much of entering sound, what would happen to its temperature?

    Nothing, since it is absorbing sound and not heatGood try, but not right. Select another answer.The temperature would go down because the sound filters out all the heatSorry, not correct. Try another button.The temperature would rise since some sound energy is turned into heat energyThat is correct.

11. Why can you hear low frequencies better through a wall than high frequencies?

    Low frequencies are absorbed more in the wall than high frequenciesGood try, but not right. Select another answer.Low frequencies start off being louderSorry, not correct. Try another button.Low frequencies are not absorbed as much as high frequenciesThat is correct.

12. If sound travels at 1000 feet/second, why does it take 2 seconds to hear the echo of a wall 1000 feet away?

    Echoes travel at 1/2 the speed of soundGood try, but not right. Select another answer.It takes sound 1 second to get there and 1 second to get backThat is correct.It only takes 1 second to hear the echoSorry, not correct. Try another button.

13. How is the Doppler effect used to measure the velocity of an object?

    The frequency of the sound changes with distance from the objectGood try, but not right. Select another answer.The frequency of the sound changes with the velocity of the objectThat is correct.The velocity of the object changes with the frequency of the soundSorry, not correct. Try another button.

14. How do bats find moths at night?

    They have very keen visionGood try, but not right. Select another answer.They listen for chirps from the mothsSorry, not correct. Try another button.They process echoes from the mothsThat is correct.

15. What happens to the speed of sound in air on a humid day?

    It increases slightly on a humid dayThat is correct.It decreases considerably on a humid dayGood try, but not right. Select another answer.Sound cannot travel when the air is extremely humidSorry, not correct. Try another button.

16. Is the speed of sound faster when the mass of the molecules of a gas is greater?

    Yes, the heavier the gas, the faster the speedGood try, but not right. Select another answer.No, because you divide by the mass in the speed of sound equationThat is correct.The speed sound in a gas equation shows that molecular mass does not matterSorry, not correct. Try another button.

17. How is music a complex sound?

    It depends on the bandGood try, but not right. Select another answer.It consists of very many frequenciesThat is correct.Reading notes is very complexSorry, not correct. Try another button.

18. Why is a good speaker necessary for music?

    So you can crank up the volume real loudGood try, but not right. Select another answer.Because it lasts much longerSorry, not correct. Try another button.It reproduces sounds more faithfullyThat is correct.

19. How does an equalizer work?

    It makes all sounds equalGood try, but not right. Select another answer.It adjusts the volumes of the different frequenciesThat is correct.It shows lights for different sounds on your stereo systemSorry, not correct. Try another button.

20. How does a piano create music?

    A hook plucks a string when you push the key downGood try, but not right. Select another answer.A small hammer strikes a string when you push the key downThat is correct.The piano key makes a noise when you push on itSorry, not correct. Try another button.

21. Where does an electric guitar use resonance?

    Only an acoustic guitar uses resonanceGood try, but not right. Select another answer.The electronics amplify through a resonant cavitySorry, not correct. Try another button.The loudspeaker bodies add amplification with resonanceThat is correct.

22. Why do some people sound better when they sing?

    Their voices produce a good combination of the right pitchesThat is correct.They know the words to the songsGood try, but not right. Select another answer.They are able to sing louder by trying harderSorry, not correct. Try another button.

23. If sound is a compression wave, why is a sine wave used to illustrate it?

    Sine waves are much louder than compression wavesGood try, but not right. Select another answer.Water waves and sound waves are the same thingSorry, not correct. Try another button.It is easier to visualize the wave when drawn as a sine waveThat is correct.

24. What would the beat frequency be if you added tones of 880 Hz and 882 Hz?

    1 HzThat is correct.881 HzGood try, but not right. Select another answer.1762 HzSorry, not correct. Try another button.

25. How could you tell that two tuning forks of the same musical note were exactly the same?

    They are exactly as advertisedGood try, but not right. Select another answer.Strike them both at the same time to verify there is no beat frequencyThat is correct.Compare each with the correct piano keySorry, not correct. Try another button.

26. How can you reduce noise at its source?

    Muffle or block out what causes the noiseThat is correct.Call the police anything some noise irritates youGood try, but not right. Select another answer.Wear earplugsSorry, not correct. Try another button.

27. What will prevent a room from being noisy?

    Eliminate its windowsGood try, but not right. Select another answer.Rugs, drapes and acoustical tilesThat is correct.Keep it airtightSorry, not correct. Try another button.

28. What does masking of a sound do?

    It produces a sound that makes the noise less obviousThat is correct.It is covering the source of the sound, often with masking tapeGood try, but not right. Select another answer.It amplifies the noise by adding irritating sounds of water flowingSorry, not correct. Try another button.

29. What happens when you add two waves that are completely out of phase?

    It doubles the volumeGood try, but not right. Select another answer.The waves become noiseSorry, not correct. Try another button.They cancel out each otherThat is correct.

30. Why does a wall vibrate from loud music?

    Sound is a vibration that affects materialsThat is correct.Walls are piezoelectric devicesGood try, but not right. Select another answer.They only vibrate to heavy metal rock musicSorry, not correct. Try another button.

Pick an answer to see instant feedback. Re-read the lesson if you miss one.

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