audio trigger keydown

first of all im a complete newbie in unity scripting, here is my question what im trying to accomplish is an audio source that plays on trigger hit like a specific key e.g space-bar and if the space bar was hit it will play the sound, i know that the script ill be using will be on the first person please help its been 2days and i only manage to play trigger music on a area

current version im using unity pro 3.4.1

Do you want something like this?