At the moment there are three options available for auto-transcribing human voice Automated online service Using open source solutions Outsourcing to a speechpany Keep in mind that auto transcript will not give you 1% accuracy. Humans do something like 96% I believe and an untrained speech recognition engine will most likely give you 638% depending on quality of the recording and the clarity of speech. As I have no idea what your files are and what you want to use the transcript for here are some general tips Automated online service If your audio files are recordings of one person speaking and there aren tons of them you could use Voice Base . Some other tools Pop Up Archive s For semi-automated transcription you could try NowTranscribe I hear it in beta and offers a free download. Haven tested it yet. Using open source solutions If you youre dealing with hundreds or thousands of recordings and have a developer handy you could have a look at the APIs available. These allow your program (for example one capturing audio) to directly query powerful speech recognition engines. Here a list %2recognition of few APIs that do Speech recognition. I haven used all of them so if you choose this path you might want to ask for some reviews. Alternatively you could have a go at CMUSphinx (it supports US English model). Outsourcing to a speechpany If youre thinking about transcribing phone calls or interactions involving two or more speakers I would rmend outsourcing to apany dealing with conversation or call analytics. Their biggest advantage is the ability to split audio into two channels and deliver lots of surrounding data. I obviously rmend Call Journey and not just because I work here!