| 摘要 |
A security monitoring means including a sound generator 110 outputting a multi-tone sound wave, comprised of a linear sum of sine waves having a plurality of frequency components, inside a monitored area. The system also includes a receiver 120 to receive the sound wave, calculate and store sound field information and a processor 130 to compare reference sound field information with the currently measured sound field information according to frequency. If a variation has occurred the processor further analyses the data to distinguish at least two events among intrusion, motion and temperature variation situations on the basis of correlation between the reference sound field spectrum and consecutive sound field spectra where rapid or gradual variation may indicate one situation over another. |
