( Hearing ( ( aids ( ( amplify sound ) ( so ( that ( it ( 's ( ( loud enough ) ( to ( be perceived ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Hearing)) (VP (VBZ aids) (VP (VB amplify) (NP (NN sound)) (SBAR (RB so) (IN that) (S (NP (PRP it)) (VP (VBZ 's) (ADJP (JJ loud) (RB enough) (S (VP (TO to) (VP (VB be) (VP (VBN perceived))))))))))) (. .)))
Hearing aids amplify sound so that it's loud enough to be perceived.
(ROOT (S (S (VP (VBN Amplified))) (, ,) (NP (PRP it)) (VP (VBZ becomes) (SBAR (S (NP (NNP louder)) (VP (VBZ happens) (VP (VB do) (NP (DT the) (NN sound)) (PP (IN during) (NP (DT a) (NN resonance)))))))) (. .)))