[SOLVED] Microphone with loud background noise

GioBonvi · 04-08-2015, 08:05 AM

Hi there!
These days I'm trying to develop a little program for speech recognition in Java.
I've met a problem which seemed insignificant, but now I think is pretty big...

To cut a long story short: my mic has a HUGE background noise. (Here you can find a recording example)

So here is what I observed:

The problem is the same with every microphone I used (I tried 4 different ones: one of them - the one I used in the attachment - is pretty costy and work flawlessly on other windows PCs)
On the same PC running Windows Vista there's absolutely no noise
The microphones work pretty well on other PC (always on windows)
The microphones have the same behaviour (heavy noise) on both my Ubuntu 14.10 and my sister's Lubuntu 14.10
There is no noticeable difference if the mic is attached to the front jack or to the rear jack
There is no difference if recording with my Java program, with audacity or with other tools

Don't know if this helps, but in audacity when I have to choose the mic it presents me a HUGE list, but my PC has only 2 jacks: front and rear. Of this list only 1 mic at time works (always one of these):

sysdefault rear mic:0
sysdefault rear mic:1
sysdefault front mic:0
sysdefault front mic:1

Front/rear depends on where I plug the jack, but I couldn't determine the 0/1 thing. Sometimes is 0 and sometimes is 1.

Here and here is the complete list of the mics displayed.

I think (don't have arguments to support this, only suppositions) this might be a driver-related issue, but, having said that, I wouldn't be able to proceed a step further, so, just in case, here is my lspci

Code:

giorgio@LINUX-GIO:~$ lspci
00:00.0 Host bridge: Intel Corporation 82945G/GZ/P/PL Memory Controller Hub (rev 02)
00:02.0 VGA compatible controller: Intel Corporation 82945G/GZ Integrated Graphics Controller (rev 02)
00:1b.0 Audio device: Intel Corporation NM10/ICH7 Family High Definition Audio Controller (rev 01)
00:1d.0 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #1 (rev 01)
00:1d.1 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #2 (rev 01)
00:1d.2 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #3 (rev 01)
00:1d.3 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #4 (rev 01)
00:1d.7 USB controller: Intel Corporation NM10/ICH7 Family USB2 EHCI Controller (rev 01)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev e1)
00:1f.0 ISA bridge: Intel Corporation 82801GH (ICH7DH) LPC Interface Bridge (rev 01)
00:1f.1 IDE interface: Intel Corporation 82801G (ICH7 Family) IDE Controller (rev 01)
00:1f.2 IDE interface: Intel Corporation NM10/ICH7 Family SATA Controller [IDE mode] (rev 01)
00:1f.3 SMBus: Intel Corporation NM10/ICH7 Family SMBus Controller (rev 01)
01:01.0 FireWire (IEEE 1394): LSI Corporation FW322/323 [TrueFire] 1394a Controller (rev 70)
01:04.0 Ethernet controller: Qualcomm Atheros AR5413/AR5414 Wireless Network Adapter [AR5006X(S) 802.11abg] (rev 01)
01:08.0 Ethernet controller: Intel Corporation NM10/ICH7 Family LAN Controller (rev 01)

My uname -r

Code:

giorgio@LINUX-GIO:~$ uname -r
3.18.7-031807-generic

If anyone could give me a hand I would be extremely grateful! Thanks!

dolphin_oracle · 04-08-2015, 09:11 AM

are you using the mix boost channel in alsamixer?. if so, turn that down as far as you can live with, and turn up the mic volume. mic boost is usually the cause of my mic noise.

GioBonvi · 04-08-2015, 02:48 PM

Thank you dolphin_oracle

That worked! I lowered the Front_Mic_Boost value and the noise disappeared. However, now the volume of the mic is exaggeratedly low... Is there any way to have it louder without touching the boost? (I have set the Front_Mic to 100 and Front_Mic_Boost to 53)

Thanks anyway!

dolphin_oracle · 04-08-2015, 03:01 PM

without knowing more about how your what your mics are and how they are configured I'm not sure. I've had the best luck with headset type mics when using my pc's analog ports. I've since switched to a couple of different powered-usb mics that show up as their own sound card in alsamixer.

One thing you can check is whether you have a "capture" volume channel setting. Think of "capture" as the "master" of inputs. So you can adjust that one up and down as well. Sometimes you even get Left and Right channels on Capture if your sound card supports stereo mics, but won't matter if you are using mono mics.

When I was using the analog mics, I used a relatively cheap headset/mic with the capture turned up fairly high and the mic jack turned up fairly high, with the mic boost about 30 or so. On my system, distortion on the mic became pretty bad around 50 on the mic boost setting.

with my open air usb mics, I get better pickup with less boost. still about the same on the capture setting, and the usb mic doesn't have a separate mic channel, just the main capture channel.

One thing you could also try is using pulseaudio. Many folks find that for some reason, the volume range under pulseaudio is better than what they get using alsa alone. Pulseaudio sits on top of alsa in most cases.

GioBonvi · 04-10-2015, 12:47 PM

Thank you for your help. I managed to get a better sound by tweaking alsamixer and pavucontrol.