Right, so the problem here, apart from people not giving a shit, is that no-one has designed a 'spirit level for soundproofing' - a tool that can be used during the job by the builder and by the supervisor to check on it. What you have is equipment that can be used after "second fix", at which point no-one wants to rip the plaster off to fix anything, so it becomes a box ticking exercise.

There are two kinds of issue: a solid transmission path that shouldn't exist ('bridge'), and a gap or void that shouldn't exist. What we need is something like a time domain reflectometer but for sound conduction, so you can detect gaps and bridges after screwing on the drywall but before skimming over it, and before the doors have been put in - ie, while there's still a massive audio path a few meters away. Ideally, even if the next panel hasn't been screwed on. If you had that, then if it detects something then all you have to do is unscrew a panel to fix it, which is something that people might actually do.

Anyone who has enough audio engineering skills, feel free to build this!

This is a really good idea. Somebody build this!

And get it into a modern certification. Want LEEDS? Get the sound measurement people out.