When a doctor listens to the heart of a person with a heart murmur, they may hear a whooshing, swishing, humming, or rasping sound. This is due to rapid, turbulent blood flow through the heart.

The first heart sound (S1) results from the closing of the mitral and tricuspid valves. The sound produced by the closure of the mitral valve is termed M1, and the sound produced by closure of the ...