What is the Relationship Between Intensity and Wattage?

[tadisc]

Homework Statement

OK, so this is a very basic question but i am uncertain what the relationship is. I know its logarithmic, but i don't know how to draw a conclusion. Here is the question:
If you want an amplifier which will give a sound output which is twice as lod as your present 20 W amplifier, what amplifier power should you buy? What if you wanted a sound output four times as loud?

Homework Equations

The Attempt at a Solution

I know that the relationship between Intensity and Wattage is logarithmic, but how do i draw a numeric conclusion?

 

[Simon Bridge]

Are they looking for loudness or intensity?

The wattage of the amplifier is the maximum power it can supply to the signal.
The intensity a wave is the square of it's amplitude.
I suspect you are thinking of decibels.

If you double the amplitude, you get four times the intensity.