This unit is about waves, and about why waves are important to noise control engineering. Waves are how sound gets from one place to another. In the source - path - receiver model used in this course, waves propagate (or travel) down the path.
This unit will introduce many basic concepts of waves: the quantities which carry the sound, the relationships between these quantities, and how we quantify these quantities. Because we will be introducing many new concepts, this unit is a bit heavy on definitions. Don't let this get you down too much, however, because we will be using these definitions over and over in this course. You will have plenty of opportunites to refer back to this unit as you progress through the course, if you need to refresh yourself on any particular concept.