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Signal-to-Noise

In the world of audio recording there’s this thing called the signal-to-noise ratio. The signal is the sound you’re trying to record, like a person’s voice. The noise is all the other sounds in the environment, like the refrigerator and the traffic and sound waves echoing off walls and floors and ceilings. Generally, good audio recordings have a lot of signal and very little noise.

One way to increase the signal and decrease the noise is to use excellent equipment and record in a sound proof studio. Very few of us, however, have these kinds of resources. Luckily, it is possible to get good recordings with inexpensive equipment (even in noisy environments) if you know what you’re doing and pay attention and wear headphones.

Before you even turn on the recorder you should think about what sounds you don’t want to record and see if you can get rid of them. Turn off background music and television sets, as these will make editing very difficult. Turn off refrigerators and fans. If you are outside, move away from traffic. Etc.

Then, when you start recording, put the microphone as close to the signal as you can without the sound distorting. For instance, if you are recording someone talking you want to put the microphone about a foot to six inches from his or her mouth. Any closer will cause distortion. Any farther away the signal will go down and the noise will come up.

To test this, sit in your kitchen and turn on your equipment. Put on your headphones so you can listen to what the microphone is hearing. Stand about six feet away from the microphone and start counting out loud. You should be able to hear the sound of your voice bouncing off the walls. This is noise.

Woman in headphones with microphone labeled Signal

Next, keep counting and move closer and closer to the microphone until you’re about a foot from it. You should be able to hear how the signal increases while the noise goes down. This is just the way microphones work. Our brains automatically shut out the noise and zoom in on the signal, but microphones don’t have brains so they hear everything equally.

It’s not easy to hold a microphone up to somebody’s mouth. To do it well you have to stand close to the person and stick the microphone though the bubble of personal space surrounding the person. It’s kind of rude, in a way. Sort of uncomfortable for both you and the interviewee, especially if you’re nervous and don’t have any confidence in what you’re doing or why.

It’s a lot easier to violate a person’s personal space if you remember you don’t really have a choice. If you hold the microphone a safe and comfortable distance from the person’s mouth then the recording will suck and you’ll have wasted the person’s time and your own as well. But if you act like you know what you are doing then the interviewee will probably relax.

The thing to do, to begin, is just turn on your equipment and put on your headphones and start paying attention to how a microphone hears things. It takes some getting used to, some practice, and even then every environment is different, every signal or thing you want to record is different, so you always need to listen for the signal-to-noise ratio and try to find ways to increase the signal and decrease the noise.

Code-animations and image-collage by Scott Bartolomei Edmonds of Smatter Inc (with photos, CC BY 2.0: Cameraman Phil’s microphone and Carolyn Williams’ new headphones.) Thanks to the Knight Prototype Fund for supporting this Transom Online Workshop resource.

Comments

  • Jay Allison

    10.22.13

    If you unplug someone’s refrigerator, put your car keys in there so you remember to turn it back on. You’ll be unpopular if you forget.

    • Patrick Collins

      10.22.13

      That’s the best reminder I’ve ever heard!

  • geo geller

    10.26.13

    ah… another signal to noise issue i find, comes from your mouth when you are interrupting somebody – so i put my finger over my mouth so when i move my lips it triggers my brain to ask… do i really need to interrupt the flow and put my two cents in – food for thought on signal to noise – a good talker is a better listener