> ...how long until someone creates a solution to scrub the audio of ads in real-time?
Let me tell you a little open secret. Ad-blocking in general can be circumvented right now. Even the most aggressive ad-blocking techniques can be brought to their knees, because they can be detected and the website can serve the content in such a way as to make ads impossible to block without ruining the content.
Not many publishers do it because publishers have chosen to not piss off the minority that has ad-blockers installed. But this minority has been growing and what you're seeing is them fighting back.
You ask how long will it take to block audio ads? It's irrelevant, because the publisher can deploy DRM in such a way as to make ad-blocking attempts illegal and easy to trace, since the streaming is done in real time from a central source. And thus users can receive big fines as to stop everyone else from doing it.
That publishers don't do this yet, that's only because they preferred to play nice with ad-blockers. But threaten their bottom line long enough and they'll fight back.
And who can blame them? Here's Spotify with a pretty good subscription model and users are now up in arms for no longer being able to get their content for free without ads.
