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[BRT] How to get rid of noise in recordings
May 17, 2012
Hello,

Welcome to the newest edition of Bedroom Recording Tips.

This issue delves into the issue of noise. What is noise, and why should we care as recording engineers? The second question should be a non-issue - we care about noise in our recordings, especially noise that's not supposed to be there. The first question, well, keep reading.

Also, there are a some questions from the readers of Bedroom-Recording.com. Some on noise, some not.

So let's go!


Noise on Recordings

A reader send me an email with quite a few questions and frustrations about noises getting on the recordings. His problems ranged from clocks in the room to electrical hum to roosters outside (see the Reader Questions section for details).

I understand the frustration of having a noise getting into the recording, but you have no idea where it came from, let alone how to get rid of it. It's not fun, and we'll see what we can do to eliminate noise on recording.

First, where does the noise come from?

Using the word "noise" is problematic, because there could be any number of different kinds. You could be getting a nearby clock, vacuum cleaner, or sister. You could be hearing internal noise on some cheap equipment. So here are the categories of noises:

  • External
  • Equipment
  • Electrical
  • Clocking

So here's some explaining for the list. An external noise is something that does not come from the equipment. This could be what you are trying to record, like a singer or guitar. Or it could be something you would rather not record, like a barking dog or a door slam.

But the more sneaky ones are the noises that are kind of quiet, but definitely there. Think a fridge, an air conditioner, a fan, or even a computer. These can all be turned when you record, and the computer can be put in another room. Be careful about things like the air conditioner. It may be so loud that the next room is still not ok.

Equipment noise is a different category. While external noise creeps in through the process of recording, it can be avoided. Internal or equipment noise cannot. It is caused by the electronics adding miscellaneous signal noise into the sound. Every piece of equipment suffers from this to a degree, but some more than others.

Cheap equipment is the worst offender. The electronics are just of soo poor quality that they cannot pass the sound through clearly. Microphones, preamps, EQs, and basically any other kind of audio that deals with analog sound suffers from this. The good news is that better quality gear means clearer signal. The characteristic sound of internal noise is a hiss, like white noise.

Another thing to keep in mind is that all microphones have what is called "self noise." It is the noise that is generated by running. Again, higher quality mics will have less self noise, but surprisingly, some world class mics exhibit a surprising amount of self noise.

Electrical noise is another term for 60 hertz hum. Have you ever noticed that some electrical plugs have three prongs while others only have two? The third is called the ground, and is there for a reason. I'm not an electrician or electronics expert, but I do know that if things are not properly grounded you get weird things. Most noticeable is a hum that centers around 60 hertz. It gets in the sound through the electronics.

It is 60 hertz (cycles per second) because the electric in the USA is running at 60 hertz - your country may be different. If you have this problem, you can solve it by using a power conditioner or by properly grounding the equipment or circuit breaker. A power conditioner is something you buy and put in between the wall plug and the equipment, sort of like a surge protector but better. It cleans up the power going through it.

Clocking noise is the final category of noise, and is maybe the weirdest. When I first started using my MOTU 2408 with my DigiMax preamp, I got a funny clicking noise every few seconds. Simply put, the noise was caused by my equipment not working together with digital sound. This problem only affects equipment that passes digital signal on, not analog. Something needs to be the master and the other the slave (seriously!) for the digital syncronization of the data stream. You probably won't have to worry about this unless you have several pieces of gear that work in the digital realm.

So there we had a brief introduction to different kinds of noise that a recording engineer might encounter while recording. Each of these types may take a bit to track down. They are elusive. But they can be fixed.


Reader Questions

Question 1: Hello! To start off, this website is awesome! There's so much information! However i am having trouble with my inputs working. I have bought a PODCASTUDIO recording bundle with a USB interface (Behringer Xenyx 502) from Best Buy online. It said that is has everything I need for music production and home recording. however it didn't teach me how to use it! I have everything hooked up right. but when I talk into my mic, it doesnt show up on the computer in Audacity when I press record. Also I have tried every recording input in prefences in Audacity and still nothing. Here is what I have: a dynamic mic (xm8500) connected to a mixer (all of the mixer levels are properly adjusted and I can see the levels of light on my mixer from green-20 to orange-6 when i speak into the mic). The mixer is then connected to a audio interface that connects through RCA cables. The audio interface (Behringer UCA200) then connects via usb to the computer. The weird thing is that I can hear sound from my laptop back to my mixer where I insert headphones into the mixer. Also the RCA cables are all working fine and have no damage or scratches. And everything is plugged in tight. So my ultimate question is, why don't I see any sound coming into my laptop?

Answer: Your problem is likely not Audacity - it is in the signal flow further back. Can you get any visual feedback from the interface? Any lights?

Where are the RCA cables coming from the mixer? Is it the mix bus or the main outputs? I'm sorry, I haven't used many mixers, so I can't say exactly which outputs are right. If I had to guess the source of your problem, I would look first to make sure that the sound is being routed through the mixer directly.

Try looking at the manual for the mixer - it looks like it should work for you. Do you need the CD out, the phones out, and is the correct output selected? Is the output volume sufficient?

Is there another RCA device that you can test the output of the mixer with? Is there another device you can test the RCA input of the interface with?

These are just basic troubleshooting steps - try isolate the problem to one piece of gear, and try to figure out what might be causing it.

Followup: First, thank you for actually responding to my email. Most times when I email someone, they dont reply but I still email anyways. Secondly, what can I say? I did the whole troubleshooting process when I thought all the cords were connected right and i actually made a mistake. So now it WORKS!!!!! I can not explain how happy I was when I first saw those sound waves on Audacity and then playing them back:) Thank you so much for your help and concern!!!!

Question 2: The second question is a rather long one that involves a computer, microphone, two wall clocks, and a rooster. It involves noise, and an interesting way to deal with it. Read about it here.


Well, that's all for this time. Please ask if you have any questions.

Lee Bedroom-Recording.com

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