What is a common expression in English that a person might say, when one suddenly got shocked by sound? For example, while a woman was walking on the sidewalk in a dark place, she suddenly heard someone yelled at her "DON'T MOVE!". what is likely going to be the first word or phrase that comes out her mouth? And what would you say to the person who yelled at you, if you recognized immediately that the person is your brother or sister.
I think it really depends on the context of the situation. For exactly the situation above, the most natural reaction for me would be to react non-verbally. For example, I would likely jerk my head out of surprise, and then face the person who shouted and examine the context. If I was actually physically startled (heart racing, etc), I might make a nonsense utterance such as "aaaaah!".