Sounds are made by vibrating objects. When an object moves back and forth, it creates sound waves in the air. As the object moves outward, the air around it gets pressed together. When the object moves inward, the air around it moves apart.
Sound waves can be represented as a curved line, or wave. A crest is a high point of the sound wave. A trough is a low point of the sound wave.
Each sound produces a different pattern of vibrations. When two sounds are mixed together, the patterns mix together to form a new pattern. When two crests meet, they form a bigger crest. When two troughs meet, they form a bigger trough. And when part of a crest and part of a trough meet, they create smaller crests and troughs.
