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02 May 2023, 07:30
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Question 1
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
65% (02:54) correct
35%
(02:38) wrong
based on 212
sessions
History
Date
Time
Result
Not Attempted Yet
Question 2
E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
45%
(medium)
Question Stats:
54% (01:01) correct 46%
(01:05) wrong
based on 195
sessions
History
Date
Time
Result
Not Attempted Yet
Though an echo is a fairly simple acoustic phenomenon—a reflection of sound waves off some hard surface—it occurs only under very specific circumstances. Imagine a listener standing at the sound source. The reflecting object must be more than 11.3 meters away from the sound source, or the echo will return too soon to be distinguishable from the original sound. A reflecting object more than about 170 meters, on the other hand, will rarely produce an audible echo, since sound dissipates with distance. Further, multiple surfaces each reflecting the same original sound to the same listener will likely not produce an echo, but a reverberation, a persistent sound gradually decreasing in amplitude until the listener can no longer hear it. Common though echoes are then, it is unsurprising that some sounds seem to produce no echo.
A centuries-old tradition holds that a duck’s quack does not echo. Scientists in the Acoustics Department of the University of Salford set out to test and explain this claim. They recorded a duck, Daisy, first in an anechoic chamber filled with sound-absorbing fiberglass wedges, then in an echo chamber with the acoustical properties of a small cathedral. The sound of the duck quacking in the anechoic chamber was clearly different from the sound of the duck quacking in the echo chamber, but the researchers acknowledged that it would be very hard to recognize an echo in the latter recording without having very recently heard the former. Partly this is because a quack isn’t a single burst of sound, but fades in and out, so that the beginning of the echo might blend with the end of the original sound. Partly it is because a quack is just not very loud. The Salford researchers also speculate that most people may simply not encounter ducks in proximity to reflectors such as buildings or mountains. A further complication, though one the researchers leave unremarked, is that people generally hear ducks in flocks, where one quack might be indistinguishable from the echo of another.
A centuries-old tradition holds that a duck’s quack does not echo. Scientists in the Acoustics Department of the University of Salford set out to test and explain this claim. They recorded a duck, Daisy, first in an anechoic chamber filled with sound-absorbing fiberglass wedges, then in an echo chamber with the acoustical properties of a small cathedral. The sound of the duck quacking in the anechoic chamber was clearly different from the sound of the duck quacking in the echo chamber, but the researchers acknowledged that it would be very hard to recognize an echo in the latter recording without having very recently heard the former. Partly this is because a quack isn’t a single burst of sound, but fades in and out, so that the beginning of the echo might blend with the end of the original sound. Partly it is because a quack is just not very loud. The Salford researchers also speculate that most people may simply not encounter ducks in proximity to reflectors such as buildings or mountains. A further complication, though one the researchers leave unremarked, is that people generally hear ducks in flocks, where one quack might be indistinguishable from the echo of another.
1. According to the passage, all of the following make an audible echo unlikely EXCEPT:
(A) a reflecting surface too close to the original sound
(B) a reflecting surface too far from the original sound
(C) multiple reflecting surfaces
(D) multiple listeners
(E) sound-absorbing materials
(A) a reflecting surface too close to the original sound
(B) a reflecting surface too far from the original sound
(C) multiple reflecting surfaces
(D) multiple listeners
(E) sound-absorbing materials
2. The passage suggests that which of the following would propagate echoes?
I. an anechoic chamber
II. a cathedral
III. a mountain
A. II Only
B. III Only
C. I and II Only
D. I and III Only
E. II and III Only
I. an anechoic chamber
II. a cathedral
III. a mountain
A. II Only
B. III Only
C. I and II Only
D. I and III Only
E. II and III Only
09 May 2023, 09:45
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how ans for ques 1 is d why it can't be option b
10 May 2023, 23:29
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stutimishra
Official Explanation
1. According to the passage, all of the following make an audible echo unlikely EXCEPT:
Explanation
The passage claims that the reflecting surface must be far enough away so that the sound of the echo is distinct from the original sound, but not so far away that the sound is completely dissipated. You can use that information to eliminate (A) and (B).
The passage also claims that multiple reflecting surfaces are apt to produce a reverberation rather than an echo, so you can cross off (C).
The anechoic chamber is said to prevent echoes with sound-absorbing fiberglass wedges, so (E) is also out.
Answer: D
Explanation
The passage claims that the reflecting surface must be far enough away so that the sound of the echo is distinct from the original sound, but not so far away that the sound is completely dissipated. You can use that information to eliminate (A) and (B).
The passage also claims that multiple reflecting surfaces are apt to produce a reverberation rather than an echo, so you can cross off (C).
The anechoic chamber is said to prevent echoes with sound-absorbing fiberglass wedges, so (E) is also out.
Answer: D
