Did i just have an auditory hallucination? how can i tell?

Reality testing: People who hallucinate experience what might appear to be sensory input when no source of the input is present. The process of reality testing allows people to act like scientists to determine whether there is an objective source of the input or whether the apparent perception is self-generated. Examining sounds further might include comparing different sounds or asking others what they hear.

Ask another : If there is another person in the room, ask that person if they heard what you did. If you are alone, and you experience hearing things in a room that should not be there, consider getting a psychiatric evaluation based on the symptoms you are experiencing.