Security monitoring apparatus and method using correlation coefficient variation pattern of sound field spectrum

1. A security monitoring method of a security monitoring device, the method comprising:

outputting a multi-tone sound wave configured with a linear sum of sine waves having a plurality of frequency components inside a security monitoring space;

receiving the multi-tone sound wave

calculating a sound field using the multi-tone sound wave;

calculating and storing sound field information according to frequency through the sound field;

determining whether a sound field variation occurs by comparing reference sound field information according to frequency with the currently measured sound field information; and

distinguishing 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 by analyzing whether the sound field variation occurs collected for a certain predetermined period.

2. The method of claim 1 , wherein the correlation is obtained by calculating a correlation coefficient value between the reference sound field spectrum and the consecutive sound field spectra.

3. The method of claim 1 , wherein the correlation is obtained by using a correlation coefficient calculated by dividing a covariance value of the reference sound field spectrum and the consecutive sound field spectrum by multiplication of standard deviations of the reference sound field spectrum and the consecutive sound field spectrum.

4. The method of claim 1 , further comprising:

comparing the reference sound field spectrum and a current sound field spectrum to determine whether a dangerous situation causing the sound field variation occurs;

distinguishing an intrusion, temperature variation, or motion situation by analyzing sound field spectra collected for a certain predetermined period before the dangerous situation occurs and; and

distinguishing situations of the intrusion, motion, fire, and ordinary temperature variation comprising daily temperature range, and air conditioning and heating on the basis of the correlation coefficient between the reference sound field spectrum and the consecutive sound field spectra.

5. The method of claim 4 , wherein whether the dangerous situation occurs is determined by comparing the correlation coefficient between the reference sound field spectrum and the current sound field spectrum with a set reference value.

6. The method of claim 1 , wherein a variation pattern of the correlation coefficient between the reference sound field spectrum and the consecutive sound field spectra is used,

a rapid reduction right before the occurrence of the dangerous situation is determined as the intrusion, and

a gradual reduction right before the occurrence of the dangerous situation is determined as the temperature variation situation.

7. The method of claim 1 , wherein the intrusion and temperature variation situations are distinguished by comparing a ratio of a value obtained by subtracting from 1 an average value of the correlation coefficient between the reference sound field spectrum and the consecutive sound field spectra before occurrence of a dangerous situation and a value obtained by subtracting from 1 a correlation coefficient between a sound field spectrum at a time point of occurrence of the dangerous situation and the reference sound field spectrum.

8. The method of claim 1 , wherein a temporal variation aspect of a correlation coefficient between the reference sound field spectrum and the consecutive sound field spectra is analyzed,

the irregularly increased and decreased variation aspect is determined as a motion; and

the variation aspect of rapidly reduced is determined as an intrusion situation.

9. The method of claim 1 , further comprising: determining whether a sound field variation occurs by comparing the reference sound field spectrum and a current sound field spectrum; and

distinguishing a motion of a human/animal, fire, and an ordinary temperature variation situation comprising daily temperature range, and air conditioning and heating by analyzing sound field spectra according to frequency, which are collected for a predetermined period before occurrence of the sound field variation situation.

10. The method of claim 9 , further comprising comparing the correlation coefficient between the reference sound field spectrum and current sound field spectrum with a set reference value to determine whether the sound field variation situation occurs.

11. The method of claim 1 , wherein a temporal variation aspect of the correlation coefficient between the reference sound field spectrum and the consecutive sound field spectra is analyzed,

when the variation aspect is irregular, the situation is determined as motion, and

when the variation aspect is uniformly gradually reduced, the situation is determined as temperature variation situation.

12. The method of claim 1 , wherein a correlation coefficient between the reference sound field spectrum and the consecutive sound field spectra in a predetermined period before occurrence of the sound field variation situation is used,

a ratio of a value obtained by summing absolute values of differences between adjacent correlation coefficients obtained by consecutive measurement in a predetermined period and a value obtained by subtracting from 1 a correlation coefficient at a time point of detection of the sound field variation is set as a movement index, and

the motion and the temperature variation are distinguished by using the movement index.

13. The method of claim 1 , wherein an index representing a frequency movement degree of the sound field spectrum is derived on the basis of correlation coefficients between the reference sound field spectrum and the consecutive sound field spectra, which are obtained by adopting multi-tone frequency index as a variable, and

a fire situation or an ordinary temperature variation situation comprising daily temperature range and air-conditioning and heating are distinguished by considering a direction and duration of the frequency movement.

14. The method of claim 9 , further comprising detecting and storing motion information on a human and an animal inside a security space by using sound field information; and

transmitting the detection information to a smart phone and a smart device of a protector.

15. The method of claim 9 , further comprising delivering an alarm of occurrence of accident comprising falling, fainting, and invalidity, and transmitting security information at the time when the motions of a human and an animal in the security space are not detected for a pre-determined time.

16. The method of claim 1 , wherein the security monitoring method is linked to a security camera having a network function, and smart appliances comprising an internet phone, a smart TV, and an interphone such a door-phone or a video-phone.

17. A security monitoring apparatus comprising:

a sound generating device configured to output a sound wave according to an input voltage in a security monitoring space;

a sound wave receiving device configured to receive the sound wave and calculate a sound field by using the sound wave; and

a sound field signal processing device configured to calculate consecutive sound spectrum information on the sound field through consecutive measurement, to calculate cross correlation coefficients between the consecutive sound field spectrum information and reference sound field spectrum information, and to distinguish at least two events among intrusion, motion, and temperature variation situations through the cross correlation coefficient.

18. The apparatus of claim 17 , wherein the sound wave is a multi-tone sound wave configured with a linear sum of sine waves having a plurality of frequency components.

19. The apparatus of claim 17 , further comprising a memory configured to store the reference sound field spectrum information.

20. The apparatus of claim 17 , wherein the sound field signal processing device calculates a sound transfer function by using sound pressure or a phase of the sound field.