restrained, muted, dull, hush, stilly, quiet, placid, unruffled, small, low-key, smooth, soft, low, muffled, subdued, whispery, low-keyed, dim, tranquil.
pacified (part of speech: verb)
concealed (part of speech: verb)
- covered up,
silenced (part of speech: verb)
silent (part of speech: adjective)
soothed (part of speech: verb)