Sound 2

A sound wave is different than a light wave in that a sound wave is:

• A. Produced by an oscillating object and a light wave is not.

• B. Not capable of traveling through a vacuum.

• C. Not capable of diffracting and a light wave is.

• D. Capable of existing with a variety of frequencies and a light wave has a single frequency.

A sound wave is a pressure wave; regions of high (compressions) and low pressure (rarefactions) are established as the result of the vibrations of the sound source. These compressions and rarefactions result because sound

• A. Is denser than air and thus has more inertia, causing the bunching up of sound.

• B. Waves have a speed that is dependent only upon the properties of the medium.

• C. Is like all waves; it is able to bend into the regions of space behind obstacles.

• D. Is able to reflect off fixed ends and interfere with incident waves

• E. Vibrates longitudinally; the longitudinal movement of air produces pressure fluctuations.

In the storming night, you will always see the lightning first, then hear the thunder after. When the lightning is 5 seconds ahead of the thunder, how far the cloud is way from you? (The speed of light is 3.0×10⁸ m/s, the speed of sound is 343 m/s)

• 500 m

• 1000 m

• 1700 m

• 2000 m

Two musical notes that have a frequency ratio of 2:1 are said to be separated by an octave. A musical note that is separated by an octave from middle C (262 Hz) has a frequency of _____. (There could be more than one correct choice.)

• A. 131 Hz

• B. 254 Hz

• C. 270 Hz

• D. 524 Hz

• E. None of these above

The sound level near a noisy air conditioner is 70 dB. If two such units operate side by side, the sound level near them would be

• (a) 70 dB.

• (b) 73 dB.

• (c) 105 dB.

• (d) 140 dB.

A trumpeter plays at a sound level of 75 dB. Three equally loud trumpet players join in. What is the new sound level?

• A. 78 dB.

• B. 81 dB

• C. 225 dB

• D. None of the above

A mosquito's buzz is often rated with a decibel rating of 40 dB. Normal conversation is often rated at 60 dB. How many times more intense is normal conversation compared to a mosquito's buzz?

• A. 2

• B. 20

• C. 100

• D. 200

• E. 400

On a good night, the front row of the Twisted Sister concert would surely result in a 120 dB sound level. An IPod produces 90 dB. How many IPods would be needed to produce the same intensity as the front row of the Twisted Sister concert?

• A. 3

• B. 30

• C. 100

• D. 1000

• E. 3000

Two speakers are arranged so that sound waves with the same frequency are produced and radiate through the room. An interference pattern is created (as represented in the diagram at the right). The thick lines in the diagram represent wave crests and the thin lines represent wave troughs. At which of the labeled point(s) would constructive interference occur?

• A. B only

• B. A, B, and C

• C. D, E, and F

• D. A and B

A tuning fork with a frequency of 440 Hz is played simultaneously with a fork with a frequency of 437 Hz. How many beats will be heard over a period of 10 seconds?

• 3

• 15

• 30

• 300