What other names do the heart sounds go by?
Lub, the first sound, is sometimes called S1. Recall this sound is associated with the closing of AV valves.
Dub, the second sound, is sometimes called S2. Recall this sound is associated with closing of semilunar valves.
There is also an "S3" and "S4."
S3 is associated with ventricular filling. If S3 is heard, it may or may not signify an abnormality.
However, if you hear S4, there is almost always an abnormality with atrial contraction.