Regurgitation through the mitral valve is by far the most commonly heard murmur, producing a pansystolic/holosystolic murmur which is sometimes fairly loud to a practiced ear, even though the volume of regurgitant blood flow may be quite small.
Stenosis of the mitral valve, if severe, also rarely produces an audible, low frequency soft rumbling murmur, best recognized by a practiced ear using a high quality, especially electronically amplified, stethoscope.