语言用一种语言转换为另一种语言

I have a requirement which i would like to achieve using .net.What i want is that any person who is having a mic attached should speak in some language.He can select some language from the application and the application would convert his voice into that particular language.i.e Voice-to-Voice conversion. How can i do this?Is there some third party API?How should i start?I have a requirement which i would like to achi