| 摘要 |
<p>A method and apparatus for detecting unauthorized or accidental entry of an object into a body of water is disclosed, wherein the frequency or frequency range of sound waves in a body of water generated by the entry of the object into the body of water is determined. Then the sound waves having the frequency generated in the body of water are detected and an electrical output waveform representative of the amplitude of the sound wave in the frequency is generated. The amplitude of the electrical output waveform is subsequently averaged, so that an alarm signal is generated when the amplitude of the electrical output waveform exceeds the averaged amplitude by a predetermined value in a predetermined period of time. Once the alarm signal is generated an alarm is activated.</p> |
