In Severe Aortic Stenosis there is a diamond shaped systolic murmur which lasts throughout systole. The murmur is loud and higher pitched than the murmur of mild aortic stenosis. It is caused by calcification of the aortic valve leaflets.
There is a fourth heart sound heard in late diastole (just before the first heart sound). This is caused by the increased left ventricular wall thickness and stiffness.
S1 is normal. S2 is louder than normal. In fact, you are hearing only the accentuated pulmonic component of S2 due to heart failure on the left side.
The aortic ejection click heard in mild cases of valvular aortic stenosis is gone.
In the anatomy tab you can see the greatly thickened left ventricular wall and the almost totally immobile aortic leaflets.