Sound is the wave of air molecules caused by the motion of an object. A sound wave contains energy, which means it can make things move or can be changed into other forms of energy, e.g. electrical energy etc.

Sound is produced when air the air molecules around an object vibrates. So, no movement means no sound. If object moves faster and it vibrates more which means higher frequency and louder the sound. Sound travels at different rates in different media. In dry air, sound travels at 331.6 m/sec at 0 C.