( ( Sound waves ) ( ( are ( ( very low ) ( frequency ( radio waves ) ) ) ) . ) )
(ROOT (S (NP (JJ Sound) (NNS waves)) (VP (VBP are) (NP (ADJP (RB very) (JJ low)) (NN frequency) (NN radio) (NNS waves))) (. .)))
Sound waves are very low frequency radio waves.
(ROOT (S (NP (NNP Am) (NN radio) (NNS waves)) (VP (VBP exist) (PRT (RP in)) (NP (DT the) (ADJP (QP (CD 540) (TO to) (CD 1600))) (NN khz) (NN frequency) (NN range))) (. .)))