In the TV show and in the recent movie, Agent 86 (Maxwell Smart, played by Steve Carrell in the movie) loves one of his gadgets seemingly above all others: the Cone of Silence.  The basic premise is that sound waves - in particular human speech - cannot escape the cone of silence.  Only those in the cone of silence can hear it, and those outside cannot.  Of course, it never really works, with comical results.

The thing is, many businesses approach sound masking as if it were a real version of the Cone of Silence (or C.O.S. as Steve Carrell refers to it).  However, just as in the movie and TV series, the C.O.S. does not exist in any functional form (despite what some sound masking reps may say).  You can't do "spot masking" right outside a conference room door or simply stick a single emitter or loudspeaker directly over a cubicle and call it done. 

Done right, office sound masking will provide you with exceptional speech privacy.  But make sure the sales guy explains it right.  If it sounds like he's trying to sell you a Cone of Silence, expect his system to generate about the same results.