( ( A decibel ) ( ( is ( how ( ( ( the ( ( intensity or ) loudness ) ) ( of sound ) ) ( is measured ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN decibel)) (VP (VBZ is) (SBAR (WHADVP (WRB how)) (S (NP (NP (DT the) (NN intensity) (CC or) (NNS loudness)) (PP (IN of) (NP (NN sound)))) (VP (VBZ is) (VP (VBN measured)))))) (. .)))
A decibel is how the intensity or loudness of sound is measured.
(ROOT (S (NP (NNP Decibel)) (VP (VBZ is) (NP (NP (DT the) (NN term)) (VP (VBN used) (S (VP (TO to) (VP (VB measure) (NP (NP (DT the) (NN intensity)) (PP (IN of) (NP (JJ sound) (NNS waves)))))))))) (. .)))