We cannot identify whose voices can be heard.
( We ( ( ( can not ) ( identify ( ( whose voices ) ( can ( be heard ) ) ) ) ) . ) )
(ROOT (S (NP (PRP We)) (VP (MD can) (RB not) (VP (VB identify) (SBAR (WHNP (WP$ whose) (NNS voices)) (S (VP (MD can) (VP (VB be) (VP (VBN heard)))))))) (. .)))
We are able to identify all of the voices.
( We ( ( are ( able ( to ( identify ( all ( of ( the voices ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP We)) (VP (VBP are) (ADJP (JJ able) (S (VP (TO to) (VP (VB identify) (NP (NP (DT all)) (PP (IN of) (NP (DT the) (NNS voices))))))))) (. .)))