An added sound heard when listening with a stethoscope, distinct from heart sounds or other clicks or snaps.
Can indicate a structural abnormality. But can be heard in normal hearts too, esp kids.
Or “innocent” murmur. Characteristic vibratory, crescendo-decrescendo sound, loudest along left sternal border. Never louder than grade 3. Typically gets quieter when child stands up (you would not expect a murmur caused by a structural abnormality to change).
Another innocent one, a rumble heard in the upper chest, disappears when lying down, or when neck turned or neck veins occluded gently.
Pulmonary flow murmur
Pulmonary valve closest to anterior chest wall, which might explain why you sometimes hear this. Might be confused with pulmonary stenosis or subaortic membrane.