Fundamentals

The deciBel rating of a sound indicates how intense Sound Source B is relative to Sound Source A.  By comparing the ratio of intensities of Sound B to Sound A, one can determine how much higher or lower the deciBel rating of Sound B is.
 

There are three similar versions of this question. Here is one of the versions:

Version 1:

Sound source A has a deciBel rating of 60 dB. Sound source B is 100 times more intense. What is the deciBel rating of B?


 

 

How to Think About This Situation:

Powers of 10
The deciBel scale is based on powers of 10. When using the deciBel scale to compare the intensities of two sounds, you need to determine how many powers of 10 more intense one sound is than the other sound. For every power of 10 that one sound is more intense than the other, the deciBel rating is 10 deciBel higher.

In this question, Sound B is 100 times more intense than Sound A. That's two powers of ten more intense (100 is 10•10 or 102).  So since Sound B is 100 times more intense than Sound A, determine Sound B's  deciBel rating by adding 20 deciBels to Sound A's deciBel rating.
 

Try this link to The Physics Classroom Tutorial for more help with understanding the deciBel Scale:

Intensity and the Decibel Scale
 


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