Heart sounds vary depending on where a stethoscope is placed.
Let say, if you put a stethoscope on the apex of the heart, the first sound (S1) is louder than the second heart sound (S2). On the other hand, S1 becomes smaller than S2 when the stethoscoep is moved to the basal part of the heart.
Easier to hear than to read. Click musical notes below and get it.
Apical heart sound: ♪♪♪
Basal heart sound: ♪♪♪
This rule is simple and easy to master, but surprisingly, many doctors ― even some cardiologists ― know next to nothing about the balance between S1 and S2. To be more precise, they had learned at medical callage, but has forgotten it.