He had just one more set of test to complete before calling it a night (or an early morning more likely, he didn't want to look at the timer right now). That's when he thought he heard the sound again. Coming from somewhere below his current position - even if he was supposed to be in the metaphorical wine-cellar of the system. Obviously someone else had been busy adding 'utility' layers to the new version.
Should he ignore it? Just finish of the test-set and log off, write up the commentary to accompany the automatic results and recommendations? Yeah - that would be the best thing to do. But then, if he had been the kind of guy who did the right thing - he would probably not be working for the company - most definitely not on the system - and no way what so ever on this kind of added actions.
Five minutes later he was down below, having seen the door to the lift real easily when he actually bothered to look around rather than just sticking to the test of his own boundaries and interfaces. He opened the next door - and the sound was gone. An empty room greeted him, no traces of anyone or anything that might have been making the noise. And no obvious ways out. But since the door he was standing in was impossible to make out, the other exits would probably be equally blended into the general surrounding. The craftsmanship was amazing. Classy and delicate code, blending so seamlessly into the walls that he actually put in a pin before closing the door behind him - rather safe than messed up big time inside some room so secret it made his stuff look like a regular billboard. He had almost forgot why he came down in the first place, so good was the design, so subtle the shifts, that for the first time since joining the company he actually felt that there was something to learn.
Now, he only had to find out what - then maybe how and by whom, in order to get a better grasp on the whole level below. But that would obviously have to wait - his test set was still due, no point in giving the impression that the test were overly hard (or that there were any flaws in his design). No, the exploration could surely wait another day or two - and then maybe he could do some mock-ups over the weekend. So, he started back towards the elevator - just as the sound started again. From somewhere really close by this time. He was certain of it.
...and he said am I awake, dreaming or just tuned in?