CVR Forensics
Some recent posts have expressed skepticism about the interpretation of the final "noise" recorded by the CVR.
As an avid student of accident investigation, I have seen some instances over the years (no citations at the moment, I don't recall the specific accidents) in which fairly detailed inferences were made from CVR data.
Most obviously, the pressure level of a noise or shock can be estimated from the CVR recording. This in itself may be very useful in distinguishing a chemical explosion from an impact, metal fracture, or explosive decompression. Given the circumstances of the doomed flight, it's possible that the CVR recording captured several of these in NEAR synchrony -- tiny differences in timing will themselves serve as forensic clues.
Further, modern airliners are fitted with multiple Cockpit Area Microphones (CAMs). Comparing recordings from the various microphones can help to localize the direction from which the sound came, and to distinguish a loud sound from a shock wave*.
Conclusion: the investigators may have learned much more from the CVR, than the presence of a Loud Bang.
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* I've no idea how far the shock wave from a reasonable-size IED can travel in an A321 fuselage, so I can't say whether it's possible that an explosion far aft would produce a shock wave at the cockpit.