The hea sound associated with the mitral valve is best heard:

The four valves of the hea can be auscultated at very distinct spaces. The mitral valve can be auscultated in the left 5th intercostal space, slightly below the nipple.The aoic valve can be auscultated in the 2nd right intercostal space, just lateral to sternal angle. The pulmonary valve can be auscultated in the 2nd left intercostal space, just lateral to sternal angle. The tricuspid valve can be auscultated in the 4th left intercostal space, just lateral to sternum. Ref: Color atlas and textbook of human anatomy, Vol 2, 4th Ed, page 26