how to get text from audio file?

hi.. guys i'm doing a project in image processing.. for my application to start I required to take the text from a audio which is pre-recoded. I know there is a tts file which gives voice to text using Net.addAssembly

in similar way using Net.addAssembly. I required the code for speech to text (or) audio to text.. I required it immediately.. If anyone tried it please post to help me..

or if u know that, what are all the class I required from Net.AddAssembly to invoke to get the text from the audio. please let me know as soon as possible..

thanks in advance..