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The Issue Getting a hum in audio recording (ACX) When I move the mic around in the room it gets stronger or weaker in certain areas (where I know a power cable runs to a plug or through the wall) I can hear it when monitoring and when listening to the recording but only after doing the amplification for ACX

Equipment Behringer Xm8500 mic Scarlet solo 3rd gen interface Asus ROG laptop hooked to 2 hdmi monitors (3 total including laptop monitor)

The Room My studio is built in the basement its 5.5ft X 9ft its sound treated but not professionally, I record mostly in evenings so outside noise isn't an issue

I have set myself up in a way where if my mic is in a certain spot I can record and I don't have the electrical hum, however its not the most comfortable for long recordings. Also in doing this and getting rid of the steady hum, I have somehow now gotten a slight whine, I only notice it here and there. I want to think it is maybe the way I moved the cording around.

I have tried a electric conditioner, it didn't do anything. would the steady hum be RMI/EMI? would copper meshing on the walls help filter that and prevent it?

I can't change rooms, its where I have to live with. and I can't take wires out of the walls either so ya.. I also have a deadline on a book and ya its stressing me out.

3 Answers 3

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There are two ways to tackle this - the proper way & the easy way.

The proper way is to identify & isolate your source of interference. 'Hum' is going to be something at mains frequency. You're going to have to chase round the room seeing where it's loudest, whether rotating any piece of equipment 90° changes the pickup.
It might be a wire in a wall, but it could also be a display, or a light, or a computer, or just a bad cable…

Once isolated, then you can either try building Faraday cages around the affected parts, or see if correct earthing/grounding has any effect.
This is a faff, to say the least, and may not be entirely succesful.

While your spending time & effort [both physical & mental] on this, your job isn't getting done… so method two

The easy way.
This comes in two flavours.

  1. de-noising software like Izotope's RX De-hum module. Buy once, run everything through it 'forever'.

  2. Adobe's [still free for limited use, with paid options] Podcast Enhance AI.
    Throw a finished file at it, marvel at the result.

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  • I would rather do it the correct way, in my experience doing things the quick way just lead to having to do things the correct way later on anyway. my desk is a corner desk, behind where I sit is a wall socket, its not at ground level it would be about 3 ft off the ground because of the cement
    – Nevek M
    Nov 13, 2023 at 18:42
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    The likelihood of it being a mains cable in the wall is close to zero. it's going to be something more 'active' in the room, or bad earthing. Back in the days of CRT displays & guitars with magnetic coil-wound pickups, it was fluorescent lights or your computer display. It gets more complicated now, especially with cheap wall-warts for everything [which can produce a hideous whine] & laptops, which are rarely earthed at all & often the source of a myriad interferences. The modern 'office' environment is a minefield of mismatched ground levels & stray EFI/RFI.
    – Tetsujin
    Nov 13, 2023 at 18:48
  • Im more confused now then, when moving the mic around that back wall is where the noise is and the only thing in there is a power line, the other side of the wall is the garage. how can I earth or check for earthing on these things, I spent a small fortune on a conditioner which didn't help at all.
    – Nevek M
    Nov 13, 2023 at 18:57
  • You're now discovering why I advocated method two;) This can be a nightmare to track down… harder still to cure. Really, a single regular mains cable should not be causing interference across most of a room. Other factors are in play.
    – Tetsujin
    Nov 13, 2023 at 19:00
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When using a dynamic mic, switch off phantom power. It is not supposed to do anything with modern microphones, but the generation of the phantom power can produce noise.

Instead of trying different locations in the room, you can try different orientations of the microphone.

Make sure you have a good balanced XLR cable and use XLR from microphone to soundcard, without any adapters.

It's also worth checking whether you have 100 Hz hum or 50 Hz hum: the former means something in/near your room is humming mechanically, the latter means you have a magnetic field picked up somewhere (change to 120/60 Hz in U.S. and its similarly frequented electric cousins).

The microphone may pick up magnetic fields. The only way to shield that is with a cage/hull of mu-metal around the microphone, and that's sort of impractical.

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  • Moving the mic/different orientations done. And I do have a quiet spot. Its just not practical to record that way. How would I check on the hz of the frequency. Its not noticable until amplifying for the ACX check
    – Nevek M
    Nov 14, 2023 at 21:40
  • Put an electronic tuner on it. 50Hz mains is just sharp of G, 60Hz just flat of B.
    – Tetsujin
    Nov 16, 2023 at 10:23
  • @Tetsujin I should think they know whether they live in the U.S. or in Europe. The question was more one of the octave.
    – user107063
    Nov 16, 2023 at 11:50
  • That wasn't really what I meant. Mains/efi hum is rarely a single octave. 50Hz is too low for many tuners.
    – Tetsujin
    Nov 16, 2023 at 12:36
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The Behringer Xm8500 is a dynamic mic (basically a speaker working in reverse) and has a coil of wire internally. From what you describe, it sounds like this coil is picking up the magnetic field produced by the wiring in the walls and generating hum. Try using a mic that isn't dynamic like a pure condenser or electret condenser mic and see if the hum goes away. If not, as Tetsujin says, there could be quite a bit of work ahead getting to the root cause.

I was a little lazy/sloppy with my reference to "wiring in the walls" and wanted to add more information. I fully agree that properly installed wiring has very little chance of creating a magnetic field of any consequence, but improper wiring (among other things) certainly can. From your description of the problem it occurs only near the wall and nowhere else, and this suggests that one of the possible causes is a magnetic field in that area. You mention that there is a garage on the other side of the wall. Check to see what's there. Maybe an electrical panel, a piece of equipment with a power transformer, even a water pipe can cause problems if it's carrying stray current. Hope you have some luck.

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  • Phantom power is off, the other side of the wall had no power tools. None that are plugged in. Its just pegboard and cabinet with some tools. I unplugged the power bar I have there and that didnt do anything.
    – Nevek M
    Nov 14, 2023 at 21:38
  • Well it looks like you've done all the right stuff and still can't find the culprit. It still looks like a magnetic field issue (not 100%, but at the top of the list), but having eliminated all of the obvious causes leaves the tough ones like moving the AC power lines -- not something for you to do and still might not fix the problem. At this point, you should consider trying a condenser or electret-condenser mic as a test and could be used for recording also. There are mics for about US $25 that would work, or maybe you could borrow one for the test. Many on this SE could offer advice. Nov 15, 2023 at 12:47

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