To surprise or startle someone (to cause a sudden shock or fright), often by making a noise or unexpected action.
後ろから大声を出して友達を驚かした。
I startled my friend by shouting from behind.
誰もいないと思っていた部屋で人が出てきて驚かされた。
Someone came out in a room I thought was empty and surprised me.
子どもを怖がらせないように、驚かさないでください。
Please don't startle the children so they won't get scared.