James Cameron brings forward the first I've heard of acoustic sensors placed on the hull of the Titan to monitor for any potential failure of the carbon fiber. In college, I took a composites class where we went through the process of laying up an I beam type structure that was going to placed under a bending moment. It was a very enlightening experience laying down the carbon fiber sheets, pouring on the epoxy resin, and then vacuum bagging the part placed in an autoclave to cure it.
During the destructive stress test, you can clearly hear the fibers letting go in the carbon fiber. It wasn't quiet. You can hear it over the noise of the Instron stress tester we used. And when it let go, it wasn't gradual. It was similar to a cannon shot. Shards of composite material went everywhere. We had plexiglass barriers placed around the test apparatus for good reason.
James Cameron said the fact the ballast weights were dropped....he thinks they heard something that caused them alarm before the implosion. Which is another terrifying thought.