Passive acoustic diver detection

Sammanfattning: This report discusses a method to detect divers in harbour environments usingpassive acoustic detection. The goal was to achieve as high detection as possiblewithout having too high false alarm rate. A short execution time was also desirable.By using the characteristic of an inhalation a band-pass filter was applied to the signalto improve the signal to noise ratio. After the filtering an energy estimation of thesignal was made. This energy estimation was later used in a frequency analysis, whichcould tell us if there were enough energy in the frequencies that correspond to adivers breathing frequency. If this energy exceeds a threshold the detector decidesthat there is a diver in the water. To get an acceptable amount of false alarms, thethreshold was set so that the energy of the breathing frequencies had to exceed 5% ofthe energy in the frequencies above the breathing frequencies. Using this method onour data we found that the detector succeeded in finding the diver and didn’t give usany false alarms.