14 July 2010
How to reduce wind noise on your smartphone recordings
Just over 200 years ago Admiral Sir Francis Beaufort developed the Wind Force Scale for the Royal Navy. It was the first system for standardising observations of wind speed, and it did so in simple and clear language:
Leaves and small twigs in constant motion;
wind extends light flag.
Raises dust and loose paper;
small branches are moved.
Small trees in leaf begin to sway;
crested wavelets form on inland waters.
Anyone who's been out and about recording with their smartphone has probably found that wind noise starts to intrude by 3 on the Beaufort Scale: leaves and small twigs in constant motion. The dull, rasping sound of the wind moving chaotically over the microphone is distracting at best, and at worst will overwhelm every other sound present.
Smartphone manufacturers face a double problem with wind noise. Not only is turbulence present in the airflow at large, but the rectangular shape of a smartphone produces miniscule eddies around itself. The effects are least strong when the mic is positioned off-centre on the bottom edge of the phone.
With care, wind noise can be reduced further. Here are some tips on how to go about it.
First, don't rely on the sound of the breeze in your ears as a guide to how much wind noise your smartphone is picking up. It's better to attend to visual cues, like those described in the Beaufort Scale, or to how strong the wind feels against your face.
Second, trying to shield your smartphone by turning your back on the wind will help, but only a little. Walls, solid fences, and bus shelters all make much more effective windbreaks.
Third, you can use a woolly smartphone 'sock' as an improvised windshield. One with a fairly open weave will produce less muffled results than a sock with a microfibre lining. Pulling the sock about half way down the phone lets you get at the touchscreen and also creates a small but necessary air space around the microphone.
Here are a couple of short before-and-after examples. First, a smartphone recording made in St Pancras train station with some wind noise introduced by blowing on the phone:
Next, a recording made in the same spot using the smartphone sock as a windshield:
The sock produces some muffling but otherwise makes a noticeable improvement to what is probably equivalent to a slight or gentle breeze, and for not much money at all.
Editor, UK SoundMap