How can a doctor detect a heart murmur?

Physical exam: Echocardiogram, sthetoscope.

Listening: By definition, a murmur is an extra heart sound beyond the lub dup of the typical heart. You pick it up by listening through a stethoscope. You can usually define its origin with an echocardiogram, but many murmurs are just simple blood flow with a typical location and intensity and need no further evaluation.