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Home Studio Q&A:
Hissss ... Hummm ... Rrrrrrrrrrrrr
... Coping With The 'Noise Floor'
Note: In New York City on Saturday, Oct. 23, 2010, Dan Lenard teaches De-Mystifying Audio Recording & Editing. Presented by VoiceOverXtra, it's an all-day, hands-on opportunity for you to work with Dan and improve your audio engineering skills. Please click here for details, or visit:
By Dan Lenard
Voice Actor & Home Studio Master
We get a few questions every now and then about “noise floor.”
Ever hear of it? It’s not about a noisy floor (although it might be something underneath it).
I won’t get highly technical here.
When I say noise floor, I’m referring to a level of noise that is below the level of your voice, but still audible in your voice recordings.
OH, OH ...
It can come from a variety of sources and must be dealt with in order to have marketable sound from your home studio.
In my home studio consulting practice, aside from room reflectivity, it’s the most challenging obstacle to overcome.
The real problem with noise floor is that when you edit and insert silence between words or sentences, the noise is clearly heard at the cut.
  • If you are doing remote sessions via an ISDN line or Source Connect, the folks at the other end will hear it too.
  • Sometimes it is electronically induced noise from your microphone or your pre-amp.
  • Generally, it's worse with cheaper analog pre-amps.
Here are some examples:
A hiss, what we call “white” and “pink” noise.
  • This is usually produced by too much gain and not enough microphone signal.
  • It’s also a problem with older cheaper USB condenser mics which don’t have sufficient built in pre-amps.
Sometimes it’s a hum, which can be caused by a ground loop. Hunting down the source can sometimes be quite a challenge.
Then there is mechanically induced noise. Most common is, of course, a fan from a desktop computer. That low frequency rrrrrrrrrrrrrrrr.
  • Sometimes it’s multiple fans in a computer.
  • The power supply is usually the major culprit, or the CPU chip fan, and some cards that run chips like video cards, also have a fan.
The solution is to isolate your microphone as far as possible from the computer.
Also, laptops tend to be quieter than desktops.
Any HVAC (Heating Ventilation and Air Conditioning) equipment in the home, or a dishwasher, washing machine or clothes dryer can certainly send noise that you can hear on a sensitive microphone.
It’s almost impossible to totally eliminate this from a house, but you can mitigate it by turning those things off when you record.
Sometimes that’s not an option.
I once had a client who had done a great job of reducing the room reflection in her studio. But we could still hear a low frequency rumbling.
She and her husband looked all over the place to find the source. It was nowhere to be found in the home.
It turned out to be a generator at a hospital around the corner!
From a technical standpoint, we consider noise floor to be any unwanted noise measured below -40db.
The sound of a vacuum cleaner in the next room or upstairs would give you a relative reference to what that level is.
And, some programs will show you exactly what your noise floor is while recording and during playback.
For instance, Adobe Soundbooth gives me a constant readout.
Just looking at a bouncing meter won’t do it, though.
I use a digital meter for a numbered readout, and a spectrograph, which gives me a visual look at frequencies that have been recorded, and their relative volumes.
You may not think it's there, but the picture never lies!
Some techno geek colleagues of mine use an oscilloscope. I always have visions of them listening to other people's demos on the set of Mystery Science Theater 3000!
The only way to hear it and measure it clearly is to record some silence, with your mic open at the gain level at which you speak.
Then, play back your recorded silence.
If you can clearly hear things like a fan or electronic hiss or something that would be heard between sentences, that’s too loud - and is probably above –40db.
What makes it more challenging is that some frequencies are inaudible at –45 db, and some aren’t.
And, everybody’s hearing is different!
There’s really only two ways to eliminate an audible noise floor:
  • One is get rid of the source or muffle it some how.
  • The other is with what’s called a noise gate. It’s a program in your recording software that will not allow sound below a certain threshold through. It can be tricky to use and has to be set properly to be effective.
I’ll be going over tricks like a noise gate and other processing programs at our hands-on De-Mystifying Audio Recording & Editing workshop in New York City on October 23. (Click here for details.) 
Usually the first thing I hear in someone’s studio is audible noise floor.
And if these old ears - blown out by countless feedback loops in headphones in radio stations, and a couple of pucks to the head in my Ice hockey goaltending days - can hear it, it's not good!
Dan Lenard is a veteran radio personality, educator and voice talent - accredited by Society of Accredited Voice Over Artists (SaVoa), and serves on the SaVoa Advisory Board. As the Home Studio Master, he is a sought-after consultant - often solving problems by phone and email correspondence, and teaching in VoiceOverXtra webinars and workshops. He will help voice actors with home studio audio at the hands-on workshop, De-Mystifying Audio Recording and Editing, Oct. 23, 2010, in New York City.
De-Mystifying Audio Recording & Editing workshop, Oct. 23, NYC:
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Comments (2)
Tom Sikes
6/7/2011 at 4:19 PM
Thanks Dan, that's really helpful! It's stuff I had thought about because of low budget equipment. I'm broke so, gotta get creative to eliminate the noises not in my head.
Linda Naylor
10/6/2010 at 9:21 AM
Thanks for an informative article, Dan.
Can you tell me what would cause a "slightly" metallic sound?
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