qui‧et‧en British English; quiet American English
1 [intransitive and transitive] also quieten down British English
to become calmer and less noisy or active, or to make someone or something do this:
Javed Miandad appealed for calm, but he failed to quieten the protesters.
Quiet down and get ready for bed!
Things tend to quieten down after Christmas.
to reduce a feeling such as fear or worry:
I managed to quieten her fears.