Calculating Decibel Increase to Reach Pain Level

[ryty]

Homework Statement

In a pig-calling contest, a caller produces a sound with an intensity level of 90 dB. How many such callers would be required to reach the pain level of 120 dB?

Homework Equations

i don't know

The Attempt at a Solution

The way I understood it from my book, for every multiple of ten increase in decibels, you have to multiply by that number, so i multiplied 1 by 3, to get 3, but that isn't right.

 

[cepheid]

No, for every factor of ten increase in the sound intensity, you add 10 dB.

 

[ryty]

So how do i find how many callers it takes to go from 90-120dB

 

[cepheid]

That's why listing the relevant equations is important, rather than just saying "I don't know." What is the *definition* of sound intensity in decibels? That equation is certainly given in your book, and is obviously a piece of information that you need to know before you can begin to answer questions about sound intensities in dB. Post that equation, and tell me if you are able to see, from it, how to proceed. If not, I can provide further hints.