15. This graph shows how hearing ability varies with the frequency of sound in three
groups of airport inspectors. The solid line represents inspectors who had worked at the
airport for 16-20 years and had been exposed to aircraft noise. The broken line represents
inspectors who had worked for the same period but were not exposed to aircraft noise.
The dotted line is for inspectors who had worked from 1-5 years without being exposed
to aircraft noise.
Which of the following conclusions CANNOT be drawn based on the data shown above?
a. Exposure to aircraft noise does not affect hearing of sounds up to 1500Hz.
b. Humans are more sensitive to sounds at 500Hz than they are to sounds at 5000Hz.
c. Exposure to aircraft noise affects hearing ability.
d. Hearing declines with age.
The conclusion that CANNOT be drawn from the graph is option b. Humans are more sensitive to sounds at 500 Hz than they are to sounds at 5000 Hz.
Understanding the hearing ability graph
The graph compares hearing thresholds across sound frequencies for three groups of airport inspectors: long‑term exposed to aircraft noise (solid line), long‑term unexposed (broken line), and short‑term unexposed (dotted line). The y‑axis is hearing ability (or loss) and the x‑axis is frequency from about 250 Hz up to 8 kHz. At low frequencies (up to roughly 1500 Hz), all three lines are very close together, while at high frequencies the line for noise‑exposed inspectors dips markedly, indicating poorer hearing.
Correct option: why b is NOT supported
Option b: “Humans are more sensitive to sounds at 500 Hz than they are to sounds at 5000 Hz.”
This statement is about general human sensitivity across all humans, but the graph only shows data for three specific occupational groups of airport inspectors, not the whole population. Moreover, the y‑axis scale and units are not fully explained in the text snippet, so an absolute comparison of overall human sensitivity at 500 Hz vs 5000 Hz for humanity at large cannot be justified from this limited sample graph. Hence, this conclusion cannot be safely drawn.
Why the other options CAN be drawn
Option a: Aircraft noise and low‑frequency hearing
a. “Exposure to aircraft noise does not affect hearing of sounds up to 1500 Hz.”
In the graph, up to approximately 1500 Hz, the solid line (long‑term exposed) almost overlaps the broken line (long‑term unexposed) and the dotted line (short‑term unexposed). This indicates little or no difference in hearing thresholds between exposed and unexposed groups at these lower frequencies, so it is reasonable to conclude that aircraft noise has negligible effect on low‑frequency hearing up to about 1500 Hz.
Option c: Aircraft noise affects hearing ability
c. “Exposure to aircraft noise affects hearing ability.”
At higher frequencies (around 3–8 kHz), the solid line for inspectors exposed to aircraft noise drops far below the lines for unexposed inspectors. This downward shift reflects worse hearing (greater threshold / loss) in the noise‑exposed group specifically at high frequencies, so the data clearly support the conclusion that aircraft noise exposure adversely affects hearing ability, particularly for high‑frequency sounds.
Option d: Hearing declines with age
d. “Hearing declines with age.”
The short‑term, unexposed group (1–5 years, dotted line) consistently shows better hearing (higher ability / lower loss) than the long‑term, unexposed group (16–20 years, broken line), especially at higher frequencies. Since both groups are unexposed to aircraft noise but differ mainly in duration of work (and thus age), the difference in hearing suggests an age‑related decline, so this conclusion is consistent with the plotted data.
Exam takeaway: how to read such graphs
When solving hearing ability vs aircraft noise questions in CSIR NET‑type exams, first match each line with its group, then compare lines at specific frequency ranges instead of reading absolute values. Next, test each option: accept statements that compare exactly what the graph shows (between these groups and frequencies) and reject statements that generalize to “all humans” or to conditions not represented in the graph, as in option b.
