WASHINGTON — It’s a sound that jolts most people awake—even from some of the deepest sleep. We hit the snooze button, but the persistent, sometimes annoying, sound of our alarm clocks just won’t quit.

S1 and S2 are the normal heart sounds you hear when the heart valves close. Heart murmurs are extra sounds that can be heard during systole, diastole, or as a continuous sound. S3 and S4 are abnormal ...