sentences: sound wave is a kind of wave & a wave is formed by the vibration of the source spreading around from the source -> vision water is formed by the microtubules of the sink freezer around from the sink sound wave is formed by the vibration of the source spreading around from the source  vision water is formed by the microtubules of the sink freezer around from the sink & spreading around is similar to spreading in all directions -> sound waves spread in all directions away from their source