When someone speaks to you, have you ever wondered how the speech signal from the speaker moves through the air and is received by your ear? This learning activity is designed to help you answer this question and better understand the nature of sound waves.

Basically, sound waves are changes in air pressure that are caused by vibrating objects such as your vocal cords or a guitar string. Since the sound wave travels in the same direction as the vibrations, we call it a longitudinal wave. We usually use a sine wave to model and represent the loudness [amplitude] and pitch [frequency] characteristics of the sound wave.