WAV to plain ASCII String Project

We are looking for a programmer to develop a module to be incorporated in our existing system. Basically, we need that this module recognizes a WAV file consisting of spoken alphanumeric codes, and returns a plain ASCII string. We require this module as an unmanaged Win32 DLL with the fewest possible dependencies, highly efficient, thread-safe, no memory leaks, etc. We code in C/C++ so they have preference, but anything callable from these two languages will be also considered. You are free to use any 3rd-party library as long as it also complies with our requirements. Some details: ? Each WAV file will include a single (and short) alphanumeric code. ? Each code is spelled out, character by character, by a human. ? There will be ambient noise in the audio. ? Precision of 70% or higher is required**. ? A response time under 1 second will be enough. **About precision: just to be clear, we mean 70% of successfully recognized codes after hundreds, maybe t