This is particularly a problem with big advertiser networks because they can track you across many sites you visit, even if you disable third-party cookies.
It has positive uses too, like preventing click fraud and concert ticket arbitrage.
I don't think that's what stockhorn said. stockhorn said it can only identify a what browser and OS and laptop model you're using. Someone else with the same browser, OS, and laptop model would have the same fingerprint. So audio fingerprinting couldn't precisely recognize you again when you come back again.
the collision rate of their ids is stated to be 0.05%
what they do is basically collect a lot of signals from the browser (audio processing stuff being only a part of it) and then compute an id on the server.
These practices and their repercussions aren't self contained.