Answer:
When someone speaks their vocal cords vibrate. That sends sound waves through the air. It's just like dropping a rock in the water and watching the waves move out in a circle. For every different sound, there's a different wave. In the same way, when a student speaks, his/her vocal cords vibrate and send sound waves through the classroom. Sound is produced when an object vibrates, creating a pressure wave. This pressure wave causes particles in the surrounding medium (air, water, or solid) to have vibrational motion. As the particles vibrate, they move nearby particles, transmitting the sound further through the medium.
I hope this helps :)