It was sort of like a signal. Rassilon put it in the Master's mind using the time vortex, to create a link from inside the time lock, outside, so that it was possible to open a path out of it.
Though they've not really explained it too well. We've nothing beyond that, we don't know how Rassilon did it, what's making the noise, or anything specific. Just that he put it there to create a link to get out of the time lock.
As for 'how it was inspired,' the four beats were the same as a Timelord's hearts-beat. As for 'how did they do that,' the Timelords basically had 9 universes inside a computer, and could do anything they wanted to the universe from their offices.