Difficulty: Easy
Correct Answer: 80
Explanation:
Introduction / Context: Sound levels are measured on a logarithmic decibel scale, important for environmental noise control and occupational hygiene. Everyday reference points help estimate exposure severity.
Given Data / Assumptions:
Concept / Approach: Typical human voice levels: whisper ~30 dB, normal conversation ~60 dB, loud speech ~70 dB, shout ~80–90 dB, and rock concerts/ sirens can exceed 100 dB. Therefore, 80 dB is a representative single-number answer for a shout, suitable for MCQ contexts.
Step-by-Step Solution:
Align daily references: conversation ~60 dB.Increase for shouting by ~20 dB → around 80 dB.Check options and select the plausible typical value: 80 dB.Verification / Alternative check: Occupational noise charts commonly place loud human vocal effort in the 80–90 dB range at close distance.
Why Other Options Are Wrong:
25 / 50 dB: Too quiet; 50 dB corresponds to a quiet office or subdued conversation.120 dB: Extremely loud; near aircraft engine/PA systems—far beyond normal shouting.Common Pitfalls: Forgetting that the decibel scale is logarithmic: a 10 dB increase represents a tenfold increase in intensity and is perceived as roughly twice as loud.
Final Answer: 80
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