also: ぴこーん · ぴゅーん
expression
Onomatopoeic expression for a clear, high-pitched ringing or pinging sound, often used in manga to indicate a sudden realization, a notification, or a sharp impact.
彼の頭の上で電球がピーンと光った。
A light bulb went 'ding' above his head.
メッセージが届くと、スマホがピーンと鳴った。
When a message arrived, the smartphone went "ping."