The last post was the sound of a heart murmur, a Patent Ductus Arteriosus (PDA), I believe. It is described as "continuous, machine-like". I first heard it last week and it gave me chills. And bad memories: I instantly recalled the tone and cadence from the muffled drums in President Kennedy's funeral procession. Muffled drums are common in military funerals. The sound and cadence are, in fact, supposed to mimic a beating heart.