Main focus of this lecture is to present on Telecommunication Sound Waves. Sound energy travels in the form of waves. Sound can travel through solids , liquids and gases by vibrating the particles in the three types of materials. The particles in the three materials vibrate in the same direction as the wave motion. This wave is called a Longitudinal Wave. Sound waves cannot travel in a vacuum. These waves then vibrate our ear drums which then activate small bones in our inner ear.