You do realize that there is always external stimulus around right?

Be it the noise of the ventilation system, or car horns outside, true silence rarely exists.

That said, when I am at home there is little else except for the sound of my computer fans as I read a book. But when I am at work, I most certainly choose to control what background noises I listen to. Music is most certainly a part of that.

As for stimulus shutting down self reflection, I find that quite the opposite is true. Different forms of stimulus encourage different forms of self reflection.