Intrusion detection based on the sound field variation of audible frequency band

가청 주파수대 음장 변화 측정 기반 침입 감지 기술

In this paper, intrusion detection technique based on the sound field variation of audio frequency in the security space is proposed. The sound field formed by sound source can be detected with the microphone when the obstacle or intruder is positioned. The sound field variation due to the intruder is based on the interference of audio wave. With the help of numerical simulation of sound field formations, the increase or decrease of sound pressure level is analyzed not only the obstacle, but also the intruder. Even the microphone is positioned behind the source, sound pressure level can be increase or decrease due to the interference. Frequency response test is performed with Gaussian white noise signal to get the whole frequency response from 0 to half of sampling frequency. There are three security cases. Case 1 is the situation of empty space with and without intruder, case 2 is the situation of blocking obstacle with and without intruder, and case 3 is the situation of side blocking obstacle with and without intruder. At each case, the frequency response is obtained first at the security space without intruder, and second with intruder. From the experiment, intruder size of $50cm{\times}50cm$ can be successfully detected with the proposed technique. Moreover, the case 2 or case 3 bring about bigger sound field variation. It means that the proposed technique have the potential of more credible security sensing in real situation.