Search Result for "louden": 
Wordnet 3.0

VERB (2)

1. become louder;
- Example: "The room loudened considerably"

2. cause to become loud; 



WordNet (r) 3.0 (2006):

louden
    v 1: become louder; "The room loudened considerably" [ant:
         hush, pipe down, quiesce, quiet, quiet down,
         quieten]
    2: cause to become loud [ant: hush, hush up, quieten,
       shut up, silence, still]