quiet down

quiet down (third-person singular simple present quiets down, present participle quieting down, simple past and past participle quieted down)

1. (intransitive, US) To become quieter.

   As the lights dimmed the general noise quieted down.

2. (transitive, US) To make someone or something become quieter.

   The teacher did her best to quiet the children down.

3. (intransitive, transitive, US) To diminish in intensity.

   Diplomacy can only begin when the violence quiets down.

• quieten down which is preferred usage in UK.