If you are hearing the acoustic sound of the drums amplified through the sound system along with the electronic sounds coming from Sensory Percussion, then you need to turn off input monitoring on your interface.
To mute the sound of the sensors, it's often as simple as turning a physical knob on your interface labeled input monitoring, or monitor balance, or direct monitoring all the way down. But on many interfaces this must be done inside the interface mixing software or driver you installed when you setup your interface, and may involve clicking a mute button on each channel that supports a sensor, or selecting a preference such as "DAW playback mode" in the top menu. Refer to the documentation provided by your interface's manufacturer if you are having trouble muting the input. And then, if you are still having trouble, message us at firstname.lastname@example.org with the make and model of you interface and we will help you out.