How do I compare 2 audio files, returning a percentage of difference
Could you please define the "percentage of difference"?

For example, please tell us which value do you expect to get:


Between two versions of the same file encoded with different settings?
Between two versions of the same file, except that one is slightly faster than the other?
Between two recordings of the same audio input, but through different microphone/recording equipment?
Between two recordings of the same person saying the same word?
Between two recordings of the same person saying the same word, with a different prosody (rhythm/melody)?
Between two recordings of different persons saying the same word?
Between two recordings of the same person saying the same sentence except for a few words?
Between a recording of a person and that of a cow?
Between a recording of an airplane and music?


What do you want to measure? The speech contents (words)? The melody, rhythm? The overall audio similarity? Encoding/recording equipment differences?