Uncertainty principle - Wikipedia Can't find better explanation why it's impossible, they should taught you in physics classes that you can't determine both - time and space same time. What is the nature of sound? You would get better results filtering high freq. , and leaving low part out of measurements. Think about ocean's wave, there are no two similar, doesn't matter how precise you set comparator, single drop of water would affect your results.
And what kind of comparator are you using? How you amplify mic's? Do you set external interrupt in microprocessor correctly?