Webkit speech recognition in audio file

I am working on a small web application and have successfully used web speech recognition in Chrome to output speech to text using a microphone using example 4 from here: https://dvcs.w3.org/hg/speech-api/raw-file /tip/speechapi.html#examples-recognition

I was wondering if anyone knows if it is possible to use an audio file as audio input instead of using a microphone?

Any suggestions would be greatly appreciated! TIA