Environmental health: noise measurement: practice question

A PSM question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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PSM · Environmental health: noise measurement

Sample item

A single machine in a workshop produces 80 dB at the operator's position. A second identical machine is switched on next to it. What is the approximate combined sound level?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. 83 dB

The decibel scale is logarithmic. Doubling the sound intensity adds about 3 dB (10 x log of 2 is about 3), so two identical 80 dB sources give about 83 dB. A rise of 10 dB corresponds to a tenfold increase in intensity.

Option by option

  • A. 80 dB

    A second source does raise the level and the total cannot stay at 80 dB.

  • B. 90 dB

    A 10 dB rise would need ten identical machines, not two.

  • C. 83 dB (correct)

    Correct. Doubling intensity adds about 3 dB.

  • D. 160 dB

    Decibels do not add arithmetically, so 80 + 80 is wrong.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More PSM questions

Questions about this PSM question

What is the answer to this PSM question?

The best answer is C, 83 dB. The decibel scale is logarithmic.

Why is "80 dB" not the answer?

A second source does raise the level and the total cannot stay at 80 dB.

Why is "90 dB" not the answer?

A 10 dB rise would need ten identical machines, not two.

Why is "160 dB" not the answer?

Decibels do not add arithmetically, so 80 + 80 is wrong.

What concept does this question test?

It tests Environmental health: noise measurement in PSM. Doubling the sound intensity adds about 3 dB (10 x log of 2 is about 3), so two identical 80 dB sources give about 83 dB. A rise of 10 dB corresponds to a tenfold increase in intensity.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Environmental health: noise measurement?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.