noun
alarm bell; warning bell
A bell rung rapidly to warn of danger, such as a fire or attack. Often used in the phrase 早鐘を打つ (to ring an alarm bell) and metaphorically for a pounding heart.
火事を知らせる早鐘が鳴り響いた。
The alarm bell rang out to warn of the fire.
胸の早鐘がなかなか治まらなかった。
The pounding of my heart wouldn't calm down.