Understanding "compression" ratio.

What is compression?  Simply put, compression in sound is a way of trimming the levels to take them to a different level and give the signal a different shape. Now, one of the factors in compression is the ratio. So, what is it?

Well just like with any proportion, the ratio in compressor is given by a proportion as well. Therefore, a ration of 5:1 could be understood like a fraction. What this means is that the signal above a certain threshold will be compressed to a proportion of 1/5 the original. So, without getting too complicated:

A ratio of 5:1 in compression simply represents a compression in signal level of 1/5 the original. 

Compress the heck out of what you need :)