( ( These waves ) ( ( ( ( require ( ( ( some type ) ( of medium ) ) ( to ( travel through ) ) ) ) , ) ( just ( like ( ( sound waves ) do ) ) ) ) . ) )
(ROOT (S (NP (DT These) (NNS waves)) (VP (VBP require) (S (NP (NP (DT some) (NN type)) (PP (IN of) (NP (NN medium)))) (VP (TO to) (VP (VB travel) (PRT (RP through))))) (, ,) (SBAR (RB just) (IN like) (S (NP (JJ sound) (NNS waves)) (VP (VBP do))))) (. .)))
These waves require some type of medium to travel through, just like sound waves do.
(ROOT (S (NP (NNP Medium)) (VP (VBZ is) (NP (NP (DT the) (NN matter)) (SBAR (WHPP (IN through) (WHNP (WDT which) (NN sound))) (S (NP (NNS waves)) (VP (VBP travel)))))) (. .)))