| 摘要 |
An apparatus and method of providing securing protection for a space or a room, including the steps of generating a non-directional sound wave field to fill the room to be protected, the sound wave field being inaudible to a human intruder, and detecting the non-directional sound wave field. A security measure, such as an alarm unit, is triggered responsive to the detected non-directional sound wave field in response to a minute change in the confines of the room to be protected, but not in response to movements in the room.
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