I am working on a natural language processing engine. It uses the Google Speech API to transcribe short recorded spoken audio and then the interpreter tries to make sense of it.

I now want to calculate the phonetic similarity between two strings, preferably in javascript. Not compare two audio files because the words or phrases are from different speakers.

For the sake of example beef and leaf sound 87% the same. The words deaf and cave something like 29%. (made up percentages)

A value between 0 and 1 is obviously fine too. Same difference.

Any ideas? Is this impossible?