After videoing something outside, I found that, although I hadn鈥檛 noticed it being windy at the time, the recording played back a very obvious wind noise. Why did the wind noises seem much louder during playback?
鈥� In my spare time, I work as a sound engineer for a group of amateur video-makers. We find that wind noise can be a problem when recording on location.
The nature of the sound heard will depend on the shape of your ears and the direction in which you are facing relative to the wind. Conditions will be different for the microphones fitted to the camera, causing the sound heard on playback to vary from what your ears pick up.
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In addition, the brain is accustomed to processing background noises, and will suppress them to the point that they are almost unnoticeable. When your brain processes the sounds on the recording, however, they are suddenly very apparent.
Sound engineers cover outdoor microphones with a furry 鈥渨ind-gag鈥�. These are sometimes referred to as 鈥渄ougals鈥� because they resemble the shaggy dog of that name on the children鈥檚 TV show The Magic Roundabout. They have the effect of reducing air velocity while allowing the pressure changes that carry the sound to pass through.
On location, a sound engineer will always monitor the recording via headphones and so will be more aware than the rest of the crew of unwanted sounds, such as wind noise and the rumble of passing vehicles.
Chris Finn, Beverley, East Yorkshire, UK
鈥� Wind noise has a spectrum that is tilted massively towards low frequencies. By contrast, our ears鈥� sensitivity drops off steeply in the lower octaves. Thus we tend not to hear wind noise as very loud in normal life.
As a designer of microphone windshields, I know that mics 鈥� particularly modern ones 鈥� can have a frequency response that is nearly flat, even at very low frequencies. If they are used without an adequate windshield, the low-frequency content of wind noise can easily drive them and other audio equipment into overload, even though it doesn鈥檛 sound very loud to our ears.
Overloads at frequencies too low for us to hear lead to short-term gaps in the recording, during which the amplifier suppresses all incoming sound. The result is a sort of syllabic muting effect or whumping. This is far more intrusive than the simple sound of onrushing air, and is the characteristic recorded 鈥渨ind noise鈥� that your correspondent objects to.
鈥淥verloads at frequencies too low for us to hear lead to a sort of whumping on the recording鈥�
Chris Woolf West Killatown, Cornwall, UK
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This article appeared in print under the headline 鈥淏lowin鈥� in the wind鈥�