Tests conducted by the THRESHER Court of Inquiry - described by the archived link - confirmed that high-velocity water-jets entering a submarine pressure-hull at great death will generate extreme levels of acoustic energy. Such energy can consist of multiple (more than 100) resonances in the low- to mid-frequency spectrum.

The frequencies of such resonances are a function of the dimensional parameters of the objects directly or indirectly impacted by the high velocity water-jet. The water-jet not only excites the pressure-hull as it passes through the breach with a velocity in excess of 2000 mph, the jet, upon impacting internal structures, acts like a pneumatic jackhammer.

Essentially, the submarine pressure-hull responds like an enormous bell being continuously struck by an equally outsized hydrostatically-driven clapper.

Impacted internal structures connected to the pressure-hull, bulkheads or decks respond like drumheads which resonate - as noted above - at frequencies that are a function of the dimensions - especially the thickness - of the component members of the excited structures.

The noise levels of many of these resonances are sufficient to be detected by SOSUS at ranges limited only by the bathymetry of the ocean area in which the event occurs.

Therefore, the presence/absence of resonances before the hydrostatically-driven collapse of a submarine pressure-hull at great depth is an unambiguous indication of whether or not major flooding occurred before collapse.