The Argentine Navy later reported that sonar systems on two of its ships and sonar buoys dropped by a US P-8A Poseidon aircraft detected noises possibly coming from San Juan; a senior United States Navy officer told CNN that this sounded like banging on the hull in order to alert passing ships;[21][22][23] later analysis of the audio determined that the sound "did not correspond to a submarine", and was probably of biological origin.
Left hanging in suspense wondering..