Sound energy travel on a ______ wave. Sound travel through a ______. Sound travels better a through a _______ medium, than a _______ medium. A sound wave is made up of two parts; compression and refraction. The _______ represent areas where the molecules are further apart. The distance from the end of one whereas, a _______ is where the molecules are further apart. The distance from the end of one compression to the beginning of the next compression is called the _________. The more waves per second the _________ the frequency. The greater the frequency the ________ the pitch. The more force put into the pulse (which start the sound) the greater the _________ of the sound. Therefore, the sound will be louder.