静かになった

became quiet

→ 静かだ
phrase Rare #23,851
became quiet Used when a place, sound, weather condition, or group of people becomes quiet or calm. The なった ending indicates a change of state in the past.
JA: 子どもたちが帰ると、教室は静かになった。
EN: When the children went home, the classroom became quiet.

やがて静かになった

It eventually became quiet.

ピッツバーグになるルフトハンザ静かになった

Pittsburgh is profitable, and Lufthansa has quieted down too.

— グッドフェローズ (1990)

海が静かになった

The sea became calm.

森の中再び静かになった

The forest grew quiet again.

ようやく静かになった

It’s finally quiet.

— 預言者 (2009)

群衆は静かになった

The crowd fell silent.

その知らせを聞くとすぐに誰もが静かになった

As soon as they heard the news, everyone fell silent.