SOLVED: Hikvision microphone static noise/humming which starts right after the boot sequence is done

Discussion in 'Hikvision' started by ethaniel, Jun 12, 2019.

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  1. ethaniel

    ethaniel n3wb

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    I own a Hikvision DS-2DE4225IW-DE PTZ camera. I decided to connect an external microphone to it and noticed electric noise/humming coming through it. At first I thought that it was my faulty wiring of the microphone. However, I've also noticed that there is no noise during the booting process (when my camera checks all it's PTZ and focus functions and then drops a "Check camera success" message on the screen). The noise starts right after the booting is complete which makes me think that the problem is originating from inside the camera.

    First example: (you can hear it loud and clear at 00:06)


    Second example: (a little bit drowned in the noise of the sea, but I marked the moment where the humming starts, around 00:04)


    The microphone is powered through the same 12v that feeds the camera.
    Any ideas?
     
  2. timb999

    timb999 Getting the hang of it

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    I am pretty sure you will find this is (or is linked to) fan noise from the camera. Every Hikvision PTZ I have owned does this. It does the boot diagnostic sequence, and then just after, the internal cooling fan starts up. It is clearly audible if you stand near the camera.

    Try rebooting and running out to the camera and you should hear the fan kicking in.

    You could try having the mic much further away, or it is possible to remove the hum/whine in post production with EQs.
     
  3. timb999

    timb999 Getting the hang of it

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    In case anyone is interested in how you remove the noise with EQ, the best way is to take a good recording of the fan noise only, look at a spectral analysis of it (using Adobe Audition or Izotope RX or similar) and you will see straight lines on the display which show the dominant harmonics of the fan noise. You can then identify what Hz these are at, and apply notch EQ filters (in post production when putting clips together) to selectively remove each loud harmonic until the sound is gone/gone enough that it is not bothersome. I use Sony/Magix Vegas Edit (sometimes available very cheaply in Humble Bundles) but other programs can surely also do this.
     
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  4. ethaniel

    ethaniel n3wb

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    That's a very interesting observation and does make sense. However, the microphone is pretty far from the camera and I can't hear the fan with my ears. So my guess is that even if there is one, could the fan be sending out electrical interference instead?
     
  5. timb999

    timb999 Getting the hang of it

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    Ah ok, so yeah, it must be interference of some kind then. The way it 'spins up' definitely sounds like it is related to the fan as this is what it sounds like if you listen to it in a quiet room. So yeah, not sure how to get rid of that...different mic maybe. I have not connected mics to a Hikvision camera before so cannot really advise.

    Dunno if this thread might help which has more info about what mics you can connect and how etc...not sure if you have a passive (unpowered) or active (powered) mic and whether one might be more susceptible to interference...

    Hikvision DS-2CD2132F-IS connecting up mic
     
  6. Cameraguy

    Cameraguy Getting comfortable

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    Power the mic with a 12v .75a wall wart adapter
    I went from a 2amp to .75 and mic is super clear and no more humming
     
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  7. ethaniel

    ethaniel n3wb

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    Wow, that's really weird. Why would the amps matter? The mic isn't using that much anyways.
    Perhaps the first adapter was bad?

    Do you power the camera from the same adapter?
     
  8. Cameraguy

    Cameraguy Getting comfortable

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    No I tried several adapters.. and finally when I used a low amperage wall adapter the humming disappeared. No I have that camera running off its original power supply.
     
  9. alastairstevenson

    alastairstevenson Staff Member

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    It probably doesn't - more likely the different power supply is generating different / less electrical noise due to a different circuit implementation.
     
  10. Cameraguy

    Cameraguy Getting comfortable

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    All I know is it worked for my situation..
     
  11. alastairstevenson

    alastairstevenson Staff Member

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    I don't suppose this was an older transformer-based power supply as opposed to the current switched-mode devices?
    A bit chunky and heavy?
     
  12. ethaniel

    ethaniel n3wb

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    I use a unpowered external microphone (Dotworkz KT-MIC) which became powered with the help of this manual that was sent by the microphone manufacturer:

    screencapture-mail-google-mail-u-2-2019-06-14-18_53_24.jpg

    So what I'm doing is I'm using a 12V external adapter. The plus (positive) wire is feeding the camera and the microphone (with the help of electrical components). The ground is feeding the camera only.

    The microphone is connected to the camera through the IN and GND lines of the camera's microphone input cable.

    So since it does look that the hum is generated by the camera's fan which sends out electrical interference to the microphone, I wonder if there is a way to mitigate it.
     
  13. Cameraguy

    Cameraguy Getting comfortable

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    Yea the original heavy adapter
     
  14. alastairstevenson

    alastairstevenson Staff Member

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    That makes sense. An old style heavy transformer-based adaptor that will use a linear regulator will not generate the electrical noise that a modern switching power supply creates.
     
  15. Cameraguy

    Cameraguy Getting comfortable

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    So why does a lower amp adapter make a difference. I tried atleast 6 different ones. 1 amp and .75 amp only ones that didnt create a humming sound
     
  16. alastairstevenson

    alastairstevenson Staff Member

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    By and large - the older, mains-transformer-based (as opposed to switch-mode regulator-based) power adaptors are lower power due to size and weight and cost constraints associated with a chunky and heavy mains transformer.
    There are no switching components that generate electrical noise in the linear regulator of a power supply that just consists of a mains transformer, bridge rectifier, reservoir and smoothing capacitors, linear regulator.

    You will be able to spot the difference if you have a portable radio.
    Hold it near the power adaptor to listen to the massive electrical noise from a switching regulator, and none from a linear power supply.
    You may need to experiment with choice of radio band to find the most noise.
     
  17. Cameraguy

    Cameraguy Getting comfortable

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    Well it works for me haha
     
  18. ethaniel

    ethaniel n3wb

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    Little update - I hooked up a 9V battery to power the microphone and all the noise is gone. I'll try to get a dedicated 220V-9V adapter for the microphone and see if it works.
     
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  19. alastairstevenson

    alastairstevenson Staff Member

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    That's an interesting experiment - it confirms it's power supply noise that's the culprit.

    There are various ways to 'quieten down' a switching power supply.
    And the low-cost common ones probably really need it when audio is in play.
    Forgetting for now the addition of some output filtering, it would probably be easy enough to wrap a few turns of the output cable through the type of ferrite toroid you see on video cables as an experiment. These are 'lossy' ferrites, aimed at absorbing and blocking high frequency noise sources.
     
  20. ethaniel

    ethaniel n3wb

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    SOLVED.

    So the problem was that I was using the same power supply to power the camera AND the microphone. Initially I had only POE and I was hoping that I could use it to power both the camera and microphone (with a POE splitter and a 12v-to-9v adapter). But turns out that is not a good idea and causes static humming on the microphone. I tried 2 different POE splitters and different 12v-to-9v adapters.

    Here are my 2 failed attempts:
    1. I tried using a Galvanised POE splitter which gave me 12v on a wire. I then added a little adapter to convert 12v-to-9v on a second wire. I connected 12v to the camera, and 9v to my microphone. Still had static noise once the camera's fan kicked in.
    2. I abandoned the POE idea and layed a 220v cable and tried using a separate 220v-to-12v adapter and then hooking up an extra wire with a 12v-to-9v adapter following the method above. Same result.

    Here is what solved the problem:

    Use 2 separate adapters:
    1. 220v-to-12v and use that to power the camera (or use POE for the camera).
    2. 220v-to-9v and use that only for the microphone.

    No noise anymore.
    Here is where I'm using this setup: