A pulse (or heartbeat) is a throbbing of blood vessels as blood goes through them. You can feel someone's pulse in their wrist, thumb or neck, where vessels are closer to the skin. A normal pulse is below 100 beats per second.
A change in heart sounds might mean sickness. There are normally four heart sounds. Two of them, S1 and S2, can be heard with a stethoscope. Two other sounds, S3 and S4, can not be heard, but they can be seen using a machine called a phonocardiograph. There are many other heart sounds which are abnormal and can be heard or seen.