It would be possible to do such a thing, but it would be very dependent on the size of the region, the frequency of the EM waves, the shape of the EM waves (that is, if they are arriving from a distant source or come from a local source). The method would probably involve emitting a complementary wave, that is, one that is the same amplitude but exactly 180 degrees out of phase, to cause cancellation. So, the kind of equipment involved would include an emitting transducer (in other words, an antenna), a signal source with sufficient amplitude and frequency capability, and I think a monitor receiver to implement a feedback arrangement wherein a controller manipulates the signal source amplitude and frequency to cause a minimum signal to be heard in the monitor receiver. In this case the monitor receiver would have its own sense antenna somewhere in the region.
It would not be possible to recommend specific equipment without understanding the conditions mentioned above. In any case, detailed design of such a system is beyond the reasonable capability of a bulletin board such as this.