( ( ( ( ( ( High-frequency ( sound waves ) ) ( -LRB- ( ultrasound -RRB- ) ) ) , ) ( which ( ( can not ) ( be ( heard ( by humans ) ) ) ) ) ) , ) ( ( are ( ( bounced off ) ( ( organs and ) tissue ) ) ) . ) )
(ROOT (S (NP (NP (JJ High-frequency) (JJ sound) (NNS waves)) (PRN (-LRB- -LRB-) (NP (NN ultrasound)) (-RRB- -RRB-)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (MD can) (RB not) (VP (VB be) (VP (VBN heard) (PP (IN by) (NP (NNS humans)))))))) (, ,)) (VP (VBP are) (VP (VBG bounced) (PRT (RP off)) (NP (NNS organs) (CC and) (NN tissue)))) (. .)))
High-frequency sound waves (ultrasound), which cannot be heard by humans, are bounced off organs and tissue.
(ROOT (S (NP (PRP You)) (VP (VBP call) (NP (NP (NN sound)) (SBAR (WHNP (WDT that)) (S (VP (VBZ has) (S (NP (DT a) (NN wave) (NN frequency)) (ADJP (JJR higher) (SBAR (IN than) (S (NP (DT the) (JJ human) (NN ear)) (VP (MD can) (VP (VB detect) (NP (NN ultrasound))))))))))))) (. .)))