Reducing wind noise

I used to live in Edinburgh, a breezy city at the best of times. Once it was so windy that I could feel my second floor flat moving slightly – in a Victorian building made out of sandstone.

So I have a fair bit of experience of trying to make field and location recordings in high winds. For the uninitiated, wind on a microphone makes a rumbly distorting sound. Directional mics are especially bad for it. Here are some examples:

Wind creates very low frequency vibration in the mic diaphragm, so that the mic is essentially sending a DC current into the preamps. This not only makes a lot of sub bass, hence the rumble, but also overloads the preamps, hence the distortion.

Some people are more tolerant than me, and argue that a bit of wind noise can give a sense of weather and atmosphere.

But if wind is causing you trouble, here are some suggestions for how to reduce it.

The best solution is to avoid getting wind noise into your recordings in the first place. To achieve this you can:

1. Use appropriate wind protection. Foam windshields are not much good for outdoors unless there’s very little wind around. You need the furry things – you might have seen them on TV, thrust in front of a politician or being knocked over by footballs when a goal is scored. Wimbledon even has special green coloured ones to blend in with the grass.

Rycote make windshields in all shapes and sizes, for just about any decent mic or recorder available. Their basic wind jammers ones are cheap (from around £30) but less effective; the more sophisticated ones are more pricey, going up to around £500 depending on the options. My experience is that you get what you pay for: the more expensive ones are more effective.

2. If you’re on a tight budget consider Rode’s offerings (e.g. the ‘blimp’, ‘dead cat’ and ‘dead kitten’ models offer varying levels of protection but at lower prices than the Rycote equivalents), or try to borrow a wind protection kit from somewhere, or hire stuff – look for places that loan out broadcast sound gear, such as The Warehouse in Edinburgh and Glasgow .

Alternatively there is the DIY approach. I’ve not had much success with that myself. There are online tutorials about how to build your own windshield, so I once spent an entire weekend sourcing fake fur and disassembling several sieves, whose mesh I then heat-glued together with a reshaped wire coathanger to make a zeppelin style basket. The mic was held in place by elastic bands. The only fur I could find was luminous pink, so it looked like a tiny Elton John costume. Sadly it wasn’t very effective. Soon afterwards I managed to find funds to buy the real deal from Rycote. The sieve/fur/coathanger/Elton John job got binned swiftly. Never looked back.

3. Buy a high wind cover for your Rycote. This is a fleece layer that sits between the basket and the fur, and it adds a few dB of wind noise reduction. See here for one example. It’s not too expensive, and I think it does work, enough to be worth using. Together with the fur it reduces the high frequencies a bit, but a modest shelving boost in post (e.g. in your audio editing software), say 3dB from around 8kHz, will help with that.

4. Find shelter e.g. by angling your body into the wind and pointing the mics away, or looking for a structure that will act as a windbreak, or moving into the lee of a hill. I usually carry a rucsac with me when I’m out recording, so I sometimes dump that on the ground and put the mics in the lee of it to break up the air flow a bit.

5. Get low down. Wind shear means that wind velocity drops massively the lower to the ground you go, and increases as you go higher. Try putting your windshielded mic actually on the ground – it can help. (I’ve heard of acousticians measuring wind turbine noise by mounting miniature mics in wooden boards, with the mic flush to the surface. The boards are then placed on the ground with a windshield over the top.)

6. Use omnidirectional mics. They are more resistant to wind than directional mics. DPA 4060 miniature mics are good for this. They still need some windshielding, but in any given windshield they will perform better than a directional mic. I find that the little lavalier windjammers that fit over these mics, like furballs, are OK for a light breeze, but for anything more I have to mount the DPAs in my full Rycote suspension. But then they work great, and the combo seems to be more wind resistant than when I have directional mics mounted in the windshield.

7. Consider using contact mics or hydrophones when recording in a windy place. Contact mics will sometimes pick up a bit of the air whistling past them, but otherwise they’re immune to wind noise. And hydrophones, being in the water, won’t be troubled by unruly air flows.

8. Engage the high pass filter on your recorder. This will only be helpful if the filter is a hardware one located in the preamps. Peter Cusack once explained to me that often these filters are digital, and therefore at a point in the signal chain after any overloading of the preamps has already occurred. In that case you’re probably better off waiting until post-production and doing high pass/low cut filtering there, so you have more control over the situation (see below).

In the Sound Devices 702 that I use, the first pole of filtering is analogue, 40Hz with a 6dB per octave slope, which can definitely help reduce the overloading of the preamps from very low frequencies.

9. Avoid recording in high winds. Stating the obvious, and sometimes not possible, but worth thinking about. Wait till it’s all blown over.

If you end up with wind noise in your recordings, there are several ways to reduce it:

• Edit it out. If the noise is a problem for just a few occasional moments, you can cut out the relevant sections in your editing software and use equal power crossfades to join the bits either side back together again. This works particularly well where the recording is of a fairly continuous sound, so the crossfade won’t be too noticeable.
• Try a noise reduction program such as iZotope RX. The Advanced version of RX has a de-wind module specifically designed to remove wind noice. This software is aimed at professionals, so it’s extremely impressive but with a price tag to match. If you’re a DIY or hobbyist recordist on a budget, you could try the free demo, and if it works well for you look at monthly subscription options. Or you could look for a sound engineer who has RX Advanced and would be willing to help you for a modest fee (this is the sort of freelance audio work I often do for people – feel free to drop me a line). There is also a low cost version of RX called Elements which you could try. It doesn’t have the de-wind module, but it has a general purpose noise reduction facility called ‘voice de-noise’. My advice would be to train it on a section of wind noise using the ‘learn’ button. It can then be used to intelligently remove these offending frequencies from the whole audio file.
• Apply a high pass filter or low cut equalisation. You’ll need to play around with the frequency and slope. I suggest starting with about -6dB of shelving at around 100Hz, and then move the frequency around a bit to find the best spot. If you’re having trouble deciding on the frequency, one trick is to start with a peak EQ and boost a lot, say by +12dB or even more, and sweep around to find the frequency where the noise seems to jump out at you most. Then cut at that frequency. It’s easy to overdo it though. If you cut too much bass from everything you can end up with very thin sounding results, so proceed with caution. It will work better where the other sounds are higher frequency, e.g. most bird song isn’t going to be affected by cutting low frequencies, whereas the drone of traffic contains lots of low end so will be more adversely affected.
• Use automation to activate the filtering/EQ right at the moment when it’s needed, and then remove it afterwards. That way, the low end will be retained in the rest of the recording. In DAWs such as Logic audio you can automate the controls to achieve this. Set an EQ plugin on your channel. Turn automation  on. Again, start with a low shelf cut around 100Hz, maybe a bit higher; again play around and listen for what works best. Then find your spike of wind noise in the waveform, zoom in, and use the automation to adjust the amount of cut on the EQ. Start with the EQ gain at zero dB, then just before the noise automate it down to say -12dB, and then bring it back up again to zero. The shorter the time you cut for, the more extreme cut you can get away with. Using a slight curve in the automation line will usually be more subtle and less of an obvious edit than if you just switch the filter straight in and then out again.

This ‘how to’ guide was produced as part of a research fellowship entitled ‘Researching sonic environments: exploring audio methodologies’. Thanks to the AHRC for funding this project.