YOU SAID:

By the time you hear the siren, it's already too late.

INTO JAPANESE

サイレンが聞こえた時にはもう手遅れです。

BACK INTO ENGLISH

By the time you hear sirens, it's already too late.

INTO JAPANESE

サイレンが聞こえる頃には、もう手遅れです。

BACK INTO ENGLISH

By the time you hear sirens, it's already too late.