( ( is ( ( played , ) ( followed ( by ( a ( loud ( revving sound ) ) ) ) ) ) ) . )
(ROOT (S (VP (VBZ is) (VP (VBN played) (, ,) (PP (VBN followed) (PP (IN by) (NP (DT a) (JJ loud) (NN revving) (NN sound)))))) (. .)))
is played, followed by a loud revving sound.
(ROOT (S (NP (NP (DT The) (NN sound)) (PP (IN in) (NP (DT a) (JJ loud) (NN classroom)))) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (NP (DT a) (NN form)) (PP (IN of) (NP (NN energy))))))) (. .)))