[SOLVED] Beeping / Buzzing through mic input?

[darkstrike]

Hi all! I just finished putting together a PC from old parts I had laying around to put Mint on for a family member to borrow for the time being (Intel Core 2 Quad, 8GB RAM, Radeon HD4000 series video card).

All works perfectly, but I've noticed from testing it that the mic input has a VERY noticeable and annoying buzzing/beeping sound constantly which just won't do as this person uses Skype a lot to talk to relatives. It does this through the front OR rear mic inputs and also does it regardless of what mic I am using (I tested it with 2 different mics)..

Link to a sample with me talking as a reference to how loud the beeping/buzzing is:
https://drive.google.com/open?id=1GSJku ... 8qHZXRgrGH

I've thought it might be a grounding issue...some of the screws for the motherboard were a bit loose (not 'falling out' loose, but loose enough I could gently tighten them a bit more without them being overtightened). I also looked at the rear I/O Shield for the mobo and most of the tabs on that are touching the board other than 3 or 4 out of the many.

This motherboard was previously in a different case with a different power supply) running Windows 7 and there were no issues there.

Anybody have any suggestions or thoughts on how to fix the issue? Thanks so much!!!

[MrEen]

Try this. In the terminal, type alsamixer then press F6 to select your sound card. If one of the columns says Mic Boost, arrow over to it and try reducing it with arrow down.

[Flemur]

Link to a sample with me talking as a reference to how loud the beeping/buzzing is:
https://drive.google.com/open?id=1GSJku ... 8qHZXRgrGH

Besides being that loud, does it also sound like that?

If so, it's probably feedback, either the mic picking up speakers (but if the same arrangement works w/windows, that's not it. Edit: tho what MrEen wrote might make the setup different from windows), or some input from pulseaudio/ALSA. Try muting all the inputs except the mic you're using. (pavucontrol and alsamixer or qasmixer). I can get a similar sound messing around with qasmixer (but not w/mic), so maybe you can get rid of it that way.

[darkstrike]

Try this. In the terminal, type alsamixer then press F6 to select your sound card. If one of the columns says Mic Boost, arrow over to it and try reducing it with arrow down.

Just checked - Mic Boost is already completely off (this is a fresh install).

Besides being that loud, does it also sound like that?

Not sure what do you mean? I used Audacity to record myself talking, that's where the clip is from. The sound output to speakers (or in my case, headphones) sounds fine with no noise, if that is what you mean? You only hear the sound on the input if you record yourself and play it back. I found out it was there by doing a test call in Skype and hearing it when Skype played back the test call. I further tested it by installing Audacity and recording a clip of myself speaking and then played it back.

If so, it's probably feedback, either the mic picking up speakers (but if the same arrangement works w/windows, that's not it. Edit: tho what MrEen wrote might make the setup different from windows), or some input from pulseaudio/ALSA. Try muting all the inputs except the mic you're using. (pavucontrol and alsamixer or qasmixer). I can get a similar sound messing around with qasmixer (but not w/mic), so maybe you can get rid of it that way.

Nope - can't be picking up the speakers as there are none hooked up. My sound test 'rig' is an old Logitech chat headset with stereo headphones and a built-in boom mic. It's not the headset as the headset works fine on my Linux laptop and I've tested a different mic on the computer with the buzz/beep issue and that mic did the same thing. There are no other inputs to mute other than the 'Stereo Monitor' of whatever noise is playing on the computer from games/OS sound effects/Youtube, etc, etc. and muting that does nothing to the buzz/beeping sound.

[GS3]

I used to deal with this kind of thing all the time. The simplest approach is to try the microphone on another computer and to try this computer with another microphone. That will tell you if the problem is with the computer or with the microphone.

The oscillation is about 1310 Hz. By the sound of it (heh) it might be bad shielding, reversed lead connections, etc.

There are several things wrong with that audio. It is stereo when I assume the input was mono. No big deal but the signals are slightly different when they should be exactly the same. The audio has a DC component which should not be there. That should be corrected.

Sometimes the answer is to by a microphone for a few dollars. Sometimes some computers, especially laptops, have lousy electronics and introduce noise. I had a laptop which would introduce noise when the HDD started up and the only solution was to install an external USB sound device.

[darkstrike]

I used to deal with this kind of thing all the time. The simplest approach is to try the microphone on another computer and to try this computer with another microphone. That will tell you if the problem is with the computer or with the microphone.

Did that already - this mic works fine on a different PC and the other mic I tried on this same PC has the same issue.

The oscillation is about 1310 Hz. By the sound of it (heh) it might be bad shielding, reversed lead connections, etc.

There are several things wrong with that audio. It is stereo when I assume the input was mono. No big deal but the signals are slightly different when they should be exactly the same. The audio has a DC component which should not be there. That should be corrected.

Sometimes the answer is to by a microphone for a few dollars. Sometimes some computers, especially laptops, have lousy electronics and introduce noise. I had a laptop which would introduce noise when the HDD started up and the only solution was to install an external USB sound device.

The thing is this same mobo worked perfectly under Windows in a different case. Could it be the CASE? Or the power supply? (This is a different PSU to the one it was being used with last time). I could take it all out again and reinstall and see if the issue is still there I guess....?

[GS3]

this mic works fine on a different PC and the other mic I tried on this same PC has the same issue.

So the problem is with the PC.

The thing is this same mobo worked perfectly under Windows in a different case. Could it be the CASE? Or the power supply? (This is a different PSU to the one it was being used with last time). I could take it all out again and reinstall and see if the issue is still there I guess....?

My guess is the case, mobo, PSU, etc are not properly grounded/bonded. That's the first thing I would check

[darkstrike]

OK, I took the ENTIRE PC apart again and carefully reinstalled everything....even bending back a lot of the I/O Shield grounding tabs to make sure more of them were in contact with the ports (especially the audio jacks). Even changed the mobo standoffs and screws and installed new fiber washers between the screws and the mobo....

Absolutely no difference.

Could the interference noise be coming from the power supply through the motherboard somehow?

[GS3]

So the only thing that has changed is the metal case? Everything else is the same? PSU, MOBO, cabling, etc. All the same? The standoffs that support the mobo? Metal in both cases?

I cannot see how changing one sheet metal case for another sheet metal case *and nothing else* would affect this issue. Please confirm there are no other changes.

Normally the negative of the PSU is connected to ground/case but there can be problems with this if it is not connected or if it is connected in more than one place.

If the standoffs are metal you can try removing them and using plastic or just a piece of cardboard to insulate the MOBO from the case. If the standoffs are plastic you can try metal.

Do you have a multimeter?

[darkstrike]

As mentioned in my previous post, I changed the standoffs / mobo screws / fiber washers when I took it apart this time. The two main things that had changed between this board being in it's old system was the case and the power supply.

I finally decided to take out the power supply I had in it and put in a different third power supply this morning that I had sitting around (I no longer own the power supply that used to be in the case with this board in it's last iteration as a system).

Turns out the power supply must've been the culprit - with the no power supply there is a LITTLE noise, but no more than any other system I have built!

[GS3]

It is possible that the PSU which gives problems is not really "bad" but just grounded or connected differently. It is very possible you can make it work if you are keen on using it.

Ground loops give a lot of pesky problems and are sometimes difficult to troubleshoot.