A speaker is producing 30 W of sound. At which of the following frequencies would it sound the loudest?
a. 50 Hz
b. 100 Hz
c. 500 Hz
d. 1 000 Hz
e. 10 000 Hz
[Ques. 2] If a plane is flying at a speed so that the apex half-angle of its shockwave is 30, what is its speed if the speed of sound is 320 m/s?
a. 960 m/s
b. 640 m/s
c. 320 m/s
d. 160 m/s
e. Choose this answer if a shock wave cannot form in this situation.
[Ques. 3] If a supersonic plane is flying at increasing speed as the temperature decreases, what happens to the Mach number in this instance?
a. It stays the same.
b. It increases.
c. It decreases.
d. It can do any of the above.
e. It can do either (a) or (b) but not (c).
[Ques. 4] The fundamental frequency of a above middle C on the piano is 440 Hz. This is the tenor high A, but a convenient note in the mid-range of women's voices. When we calculate the wavelength, we find that it is
a. much shorter than the length of either a man's or woman's lips.
b. shorter than the length of a man's lips, but about the length of a woman's lips.
c. longer than a woman's lips, but about the length of a man's lips.
d. much longer than the length of either a man's or a woman's lips.
e. about the same length as either a man's or woman's lips.
[Ques. 5] On a day when the speed of sound in the upper air is 320 m/s, you fly coast to coast in the United States, a distance of about 4 850 km, in about one hour, if the Mach number for the speed of your airplane is about
a. 1.
b. 2
c. 3
d. 4
e. 5.
[Ques. 6] A source of sound waves is placed at the center of a very large sound-reflecting wall. The source emits 0.500 W of power. Two meters from the source the intensity in W/m2 is
a. 9.95 103.
b. 1.99 102.
c. 0.313.
d. 0.399.
e. 0.625.
[Ques. 7] A boat sounds a fog horn on a day when both the sea water and the air temperature are 25.0 C. The speed of sound in sea water is 1 533 m/s. How much earlier (in s) does a dolphin 1 000 m from the source hear the sound than a person in a boat that is also 1 000 m distant? (Ignore the time it takes the sound to reach the water surface.)
a. 0.652
b. 2.12
c. 2.24
d. 2.77
e. 2.90
[Ques. 8] Which of the following does not have a precise definition in terms of the physical properties of sound waves?
a. frequency
b. intensity
c. loudness
d. sound level
e. wavelength
[Ques. 9] (Do not try the following: it could kill you. This question is only about a hypothetical possibility.) If you were standing below an object emitting a fixed frequency sound falling at terminal velocity, as it approached you, you would hear the sound
a. drop in frequency.
b. stay at the same frequency.
c. increase in frequency.
d. decrease in loudness.
e. stay at the same loudness.
[Ques. 10] A person standing in the street is unaware of a bird dropping that is falling from a point directly above him with increasing velocity. If the dropping were producing sound of a fixed frequency, as it approaches the person would hear the sound
a. drop in frequency.
b. stay at the same frequency.
c. increase in frequency.
d. decrease in loudness.
e. stay at the same loudness.
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