<unk> s are heart<unk> s heard during systole.  They can be classified by when the<unk>  begins and ends, between S1 and S2.  Many involve stenosis of the semilunar valves or regurgitation of the atrioventricular valves.
Systolic heart murmur
Austin Flint murmur
Muffled heart sounds
Continuous murmur
Still's murmur
Diastolic heart murmur
Irregular pulse
Functional murmur