Reducing Noise Floor

I’m recording narration for video tutorials and elearnings, and I’d like to move into audiobooks/narration. To improve my quality, I need to eliminate the background noise.

If I set my mixer to 0 gain and the Audacity recording level to 1.00, then the background noise level (noise floor?) is around -30. I can drop the recording level down to 0.20, which limits the noise to -45 or -40, and still allows my vocals to peak at aout -6. With Noise Removal I can get background noise to -48.

This is working in my office with a home-made sound booth under a thick blanket. Is there anything else I can do to lower the background noise? Is it better to drop Audacity’s recording level and keep the mixer at 0, or should I cut the level on the mixer too?

Equipment: M-Audio Nova mic, Xenyx 802 mixer, Behringer UCA222 sound card.

From the Xenyx 802 manual:

LEVEL SETTING: To correctly set the gains of the channels, first set the LEVEL
controls of the input channels to their center positions (0 dB). Then use the GAIN
controls to increase the input amplification until signal peaks show 0 dB on the
level meter.

(If you are using more than one input, do this for each input.)
Check the level by speaking loudly into the mic (this is to set up for the maximum input level that will occur during the recording).
Ensure that the level on the meters (on the mixer) never go above 0 dB. (It’s OK if the levels are a bit below).

Then adjust the recording level on your computer so that the maximum peaks in the Audacity meter go up to about -6 dB.

I do my recording in the spare room, and I found that I can get the noise floor down to between -70 and -60 consistently with a few things in place.

I use a Focusrite SOLO Mini Preamp and Shure55SH Series II (Dynamic) mic, into Audacity 2.1.1 on a Mac mini. The preamp has a gain control, but for the Dynamic mic, I leave it all the way up. That’s the mic’s normal throughput then.
To increase the RMS levels after recording, a touch of Normalizing is all I need.

The Mac Mini - normally pretty quiet anyway, I have shielded with sound-tiles. The foam pyramid tiles for the job. I have my mic on a boom and it’s positioned right in front of my mouth, when I read the script from iBooks on the screen, same place as Audacity.
I record during the day when the house is normally very quiet anyway. I turn off anything that may surprise me. Except the barking dog !!! If I forget to close the front door, the dog sees the postman, and it’s all over …

However, that didn’t do it. I got the floor down to may -40 to -30. It was when I started to block sound behind me, and beside me, that the noise floor really came down.
I hang bed spreads on the cupboard doors, and I have a cloths drying rack, one of those expand up type things, with cloths hanging on it positioned right behind me.
I discovered that most sound that gets to the mic comes from behind me, so blocking that improves it no end. Like I said. Normally now in the range of -70 to -60. I also sit on a wooden kitchen chair. It doesn’t creak.

This is the very professional set up that I have - minus the washing on the drying rack, that gets me that low noise floor. Oh, and a mat on the floor.
I know, it looks very dodgy, but it works!

Behind that drying rack, is a large drying cupboard that holds the boiler. I hang blankets on it’s doors.
Oddly enough the walls in front of me aren’t a problem, but I have the black foam tiles along there behind the screen anyway, The cover on the table flattens any other sounds on the table from reflections. It doesn’t flatten thumps though, caused by hitting the scroll keys too hard… when turning to the next page.

I had almost given up on the idea of getting that noise floor down without spending thousands - when some one said to me “It’s the noise coming from behind you that causes the problem” They were dead right.


Thanks very much for the help guys. I hadn’t fiddled much with the mixer’s trim/gain knob, so it’s good to get some info on how it works.

What I have noticed is that I still get a significant hiss (-42db) even with the microphone unplugged, so I presume this is electrical noise somewhere in the mixer or the USB soundcard?

It’s not coming from the microphone. Dynamic (moving coil) microphones make almost no noise. The sticky part of the system is the microphone preamplifier. The first thing the microphone hits when it arrives in the mixer. Turn the mixer slider for that microphone all the way down and most of the fffffff should go away.

The Microphone Preamplifier (MicPre) has to be designed for molecular level noise considerations. I’m not joking. This sometimes smacks up against the desire to make everything cheap. Metalic Film resistors make less fffffff noise, but noisier Carbon Composition resistors cost way less.

This also gives you the mixer promotion that says things like “Now Featuring XENYX MicPres!!!” That’s why. The microphone will never get any quieter than this one step (attached).

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Thanks Koz. I knew it was something in the equipment since the noise went away with the recording level set to 0 (obvious, really) - I just hoped that maybe it was interference in the phono-to-XLR cable to my mic. Having read more reviews, it seems this is a common problem with these cheap Behringer mixers, so I’ll have to look at getting a decent microphone preamp instead.

They’re usually not that bad. How do you have it adjusted? There’s three places to adjust volume on that mixer similar to mine.

You should start adjusting with all three about 3/4 up. In particular, the upper left one, Trim should not be all the way up. Can you make volume like that?


phono-to-XLR cable to my mic.

Wait. You what? The M-Audio Nova type of microphone requires a full-on XLR cable to work. You can’t fudge that one. There is no adapter.

The Phantom Power switch toward the right needs to be on.


I purchased a BTSKY™BM-800 (Condenser) from amazon a while back and it came with such a patch cable. I think it must be to use the mic as a PC-Mic, like for Skype or something, because like the Nova, the mic is a condenser??? I’ve never tried to use it with that phone-XLR cable though, but, it did come with it. I just chucked the cable in the third draw.

Mine’s similar, but with a rotary pot for the Main mix/master level instead of a fader.

I have the Main and the mic level set to 0, and turned the mic Trim (top left pot) until the Clip leds displayed 0 occasionally when I spoke - it’s now at the 1 o’clock position. That pot seems to have very little range between being too quiet (the 20 light barely flashes) and clipping, so it was very hard to set. With this setup, I have to set Audacity’s recording level to 0.07 to get low hiss and voice peaks at -6. I can’t bring the mixer’s level or Main up from there or I’ll instantly clip in audacity.

That leaves a steady noise floor of -42 in Audacity.

As for cables, I have XLR-to-XLR for the mixer, then phono-to-phono between the mixer and USB sound card. Hence XLR-to-phono :wink: No fudging there