How could the heart sounds be affected by av valve stenosis?

Multiple ways: Valve stenosis is the narrowing of a valve opening. Most commonly this causes flow disturbances which can be heard and is caused a murmur. Think of a kinked garden hose. The higher the velocity of the blood crossing the valve the louder the murmur. Other secondary sounds can occur but are more subtle. Pictured is a stenotic aortic valve.