I think I might have an idea how they're making this work: probably, as someone already noted, they're targeting areas where piracy is prominent. What they do is, they have different sound drops in different sequences per theater house. If a copy turns up on the web or on the streets showing the drops in that sequence, it means the copy was made at such-and-such a theater, and an investigation can be further focused; maybe that means authorities can keep an eye out for individuals who attend that theater with any suspicious-looking equipment, especially if they attend damn near EVERY movie shown there in an attempt to copy every one for the pirates.
It's no different a procedure than the way the CIA tracks documents if there's a leak, or movie studios track scripts that are leaked. One out-of-place period or comma could give it away. If the period is placed after this word or that word, and that copy turns up on the Web, they can track it back and tell who leaked it.
For the record, though, I saw the film twice at my theater, a Regal, and had no problems that come to mind.