Set frequencies to listen to for audio detection?


#1

My webcam gets triggered all the time by low frequency movement from the floor above. I would appreciate if I could choose a range of frequencies which trigger the audio alert to avoid these false alerts.


#2

Your suggestion will be sent to developers.
Thanks


#3

Did you try adjusting threshold? I don’t think it’s a good idea to limit frequency range. It will affect CPU usage, and may leave real events undetected.


#4

Can someone explain in more detail how the sensitivity of audio detection works? I assume that it is decibels. I am trying to use audio detection on my smoke and water detectors with a dedicated microphone. I placed the microphone within a couple of feet from the detectors and was thinking I needed to set the sensitivity high so I avoid other noises being detected. I started at 50 and ended up reducing the sensitivity back down to 25 before it would pick up a very high decible sound from my water detector. Seems like i should adjust to the high end of the range, but not sure why i had to reduce down so far. Sounds like the same issue triforcegathering was having and I like the idea of being able to delect by frequency. I’m not interested in anything other than high pitch sound for my purposes and I can configure my pc with another CPU if necessary to have this safety features of my system work robustly.

One more thing is that the threshold bar is so small I can barely see it. Is there any wayour to make it bigger?


#5

Hi,
Audio detection works with Threshold Level (TL). This is not the same as sensitivity. When TL is set to a low value audio detection trigger and starts recording for a low sound. Using a low TL can also start recordings for noise, i.e. a sound that has nothing to do with the scenario. The TL should be set to a level that trigger the Audio detection and start a recording for a specific sound like the sound from the water and smoke detectors. If you set TL too low it will start a recording for noise. The level 0 to 255 is relative and depends on the output signal from the microphone.

Sensitivity is something else and works generally like if you have a high sensitivity it reacts to very low sounds. If one sets a sensitivity to a low value it must be very high sound levels to make the system to react. NCS use TL and therefore you had to go from 50 to 25 to have the Audio detection to start a recording.

The sound (level and frequency) from the detectors are adjusted to how our ears respond. The microphone can have a different frequency response and therefore the TL must be low for NCS to detect the signal. If you want to have a higher signal level from the microphone use another type of microphone or use an amplifier.

Using a frequency filter is certainly interesting and also very effective for noise reduction.

-Henrik