how to convert simple audio file into written text?

Hello,

I am looking for a way to decode simple voice files into text using MATLAB. During my script, I record very short audio files each containing vocalization of one letter (lets say "A"). I need a tool that will take these audio files and convert them into written characters. Can it be done with high accuracy? How?

Thank you!

[Stephen23]

http://www.mathworks.com/company/newsletters/articles/developing-an-isolated-word-recognition-system-in-matlab.html

Also search FEX and the internet. You might find something useful.