A busy road measures 60 decibels and a quiet library 40 decibels. How does the intensity of the road noise compare with the library's?

1.5 times as greatCorrect answerYour answerTwice as greatCorrect answerYour answerAbout 100 times as greatCorrect answerYour answer20 times as greatCorrect answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer C

Correct answer: C

The decibel scale is logarithmic: every 10 dB rise means 10 times the intensity.
A 20 dB rise is 10 × 10 = 100 times the intensity.

Worth noting

1.5 and 20 treat decibels like an ordinary scale, dividing or subtracting the readings.

Concept: The decibel scale
Typical timeTypical: 90 s
Your timeYours: —

The rule this testsSound

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Ten questions from Everyday Physics, at your own pace.

A busy road measures 60 decibels and a quiet library 40 decibels. How does the intensity of the road noise compare with the library's?

Explanation