Background Information 

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
soundsare mixed together,
the patterns mix together
to forma 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.