Chapter 12: Q3MCQ (page 328)
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.
Short Answer
The correct option is (b).
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Chapter 12: Q3MCQ (page 328)
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.
The correct option is (b).
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What is the intensity of a sound at the pain level of 120 dB? Compare it to that of a whisper at 20 dB.
(II)An ocean fishing boat is drifting just above a school of tuna on a foggy day. Without warning, an engine backfire occurs on another boat 1.55 km away (Fig. 12-33). How much time elapses before the backfire is heard (a) by the fish, and (b) by the fishermen?

A fish finder uses a sonar device that sends 20,000 Hz sound pulses downward from the bottom of the boat, and then detects echoes. If the maximum depth for which it is designed to work is 85 m, what is the minimum time between pulses (in fresh water)?
In which of the following is the wavelength of the lowest vibration mode the same as the length of the string or tube?
(a) A string.
(b) An open tube.
(c) A tube closed at one end.
(d) All of the above.
(e) None of the above.
Question: (I) The A string on a violin has a fundamental frequency of 440 Hz. The length of the vibrating portion is 32 cm, and it has mass 0.35 g. Under what tension must the string be placed?
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