Science behind baking powder / baking soda ratio

OK ... I'm perfecting my muffin recipe for the State Fair, but still have a question:

Why is there usually a 2:1 ration between baking soda and double-acting baking powder? I understand both affect the leavening, but I wonder why most every recipe I look at has the 2:1 ratio. I've used a 1:1 ration in my most recent batch and am very pleased with the results. But I also would like to understand the "why". Does anyone know?

alton brown might be able to help. he doesn't specifically address the 2:1 vs. 1:1 question, but goes into detail about using both soda and powder and exactly why he does it, based on the science. check out this episode of good eats called "the muffin method man."

part one: http://www.youtube.com/view_play_list?p ... -D7zwa1vUk

part two: http://www.youtube.com/view_play_list?p ... ZJBXftTnms

Thanks, Jessie! It filled in a lot of the gaps and gave me a couple of good ideas to go try. Off to the kitchen!