  We consider the problem of hiding non-stationary objects from acoustic
detection in a two-dimensional environment, where both the object's impedance
and the properties of the detection signal may vary during operation. The
detection signal is assumed to be an acoustic beam created by an array of
emitters, which scans the area at different angles and different frequencies.
We propose an active control-based solution that creates an effective moving
dead zone around the object, and results in an artificial quiet channel for the
object to pass through undetected. The control principle is based on mid-domain
generation of near uni-directional beams using only monopole actuators. Based
on real-time response prediction, these beams open and close the dead zone with
a minimal perturbation backwards, which is crucial due to detector observers
being located on both sides of the object's route. The back action wave
determines the cloak efficiency, and is traded-off with the control effort; the
higher is the effort the quieter is the cloaking channel. We validate our
control algorithm via numerical experiments in a two-dimensional acoustic
waveguide, testing variation in frequency and incidence angle of the detection
source. Our cloak successfully intercepts the source by steering the control
beams and adjusting their wavelength accordingly.
