Question

The graph given here shows the frequency of sound emitted by a source for 30 seconds. For how many seconds a normal human being be able to hear the sound?

• A. 25 s
• B. 10 s
• C. 20 s
• D. 30 s

Answer 1

The correct option is C 20 s

Audible range for human being is 20 Hz to 20 kHz.
From the graph, the time interval in which a normal human being be able to hear the sound below 20 kHz starts from 5 seconds and end at 25 seconds, beyond this range the sound is above 20 kHz and will not be audible to human beings.
Hence, the duration in which a normal human being be able to hear the sound is 20 s.