For audio detection, the device (ex. DirectIP camera) calculates the average power of audio signal that is transmitted for specific times (6.5 seconds).
If current audio signal’s power is much higher than the power threshold of audio signal (based on the average power of audio signal), then audio detection is enabled.
That is,
- Gather audio signal for 6.5 seconds
- Calculate the average power of audio signal
- Compare current power of audio signal with the power threshold of audio signal
- Decide whether audio is detected or not.
The threshold of power level is determined by the audio sensitivity level.
* Sensitivity level 1: two times (6dB) higher than the average power of audio signal
……..
* Sensitivity level 5: 1.2 times (1.6dB) higher than the average power of audio signal