Alarm system with variable warning signal

摘要

An alarm system and method for detecting an intruder and making an impression on the intruder. The system operates by detecting a presence of the intruder, determining a location of the intruder, outputting a warning signal for perception by the intruder, and changing the warning signal based on the determined location of the intruder and/or a predetermined passage of time. The system provides means for changing an audio level of the warning signal gradually so as to give the intruder an impression that an audio source is moving toward the intruder. In a preferred embodiment, the warning signal is output over a plurality of speakers, and a phase and audio level of the warning signal output from a first speaker is changed relative to a phase and audio level of the warning signal output from a second speaker so as to give the intruder an impression that an audio source is moving two dimensionally toward the intruder. The kind of warning signal can be changed based on a predetermined passage of time or on the calculated position of the intruder. The system provides an effective alarm system by giving intruders the impression that vital beings have detected their intrusion.