My MacBook Pro is ticking like a clock. Is this normal?

I have a 13 inch 2015 MacBook Pro retina with a 2.7GHz processor, 16GB memory, 256GB storage and OSX El Capitan 10.11.3. It is about 3 months old.

Today, I have noticed that it is literally ticking like a clock or a watch - it makes a very faint, regular ticking noise every second. The sound is just like that of an analogue watch. It is so quiet that I need to put my ear right up to the source of the sound, which is in the gap between the screen and the keyboard, in the very middle. I have set my clock on my screen up to show the seconds, and it ticks exactly when the second changes. This sound is not coming from the speakers because when I mute the speakers the ticking carries on.

I presume it is something to do with the laptop's clock as it is making this noise exactly on the second just like an analogue clock. Presumably though, an apple laptop doesn't contain an analogue clock, gears and all, to tell the time. Given this, what the **** is making the noise? Is this normal? Should I have anything to worry about?