Lecturers and speakers often record their presentation’s audio and appoint somebody to transcribe it. By converting the audio into text files, the audio can be made searchable on the web, making it easier for others to find. A web service that lets you perform this task with greater ease is VoiceBase. VoiceBase lets you upload audio files and transcribe audio to text automatically online.
http://www.makeuseof.com/dir/voicebase-transcribe-audio-to-text-automatically/