the physics involved?

a jammer is a active transmitter that sends a stronger signal then the one you want to recieve.

as for it being a sink, you will need a wall of phones more or less, and stand in the direct "shadow" of that wall.

best way to envision it is like a thin piece of fabric in front of a lamp. it may produce a darker area on the opposite wall, but it will not darken out the whole room unless you basically wrap it around the lamp...