Minimizing Wind Noise
Reducing wind noise on a location shoot
By Ben Longden
Nothing annoys me more on a location shoot than wind noise. In fact I've had more than an earful of it, and decided to do something serious about it.
The occasion was on location at a major horse stud, filming a tutorial for my client, a major veterinarian firm in northern Victoria. Up until now, all previous talking head pieces had been done in the stables; this time however, it was to be an outside shoot for a specialist tutorial, but a strong wind had sprung. REALLY strong. The talent was around 30 metres from the camera and wearing a radio microphone clipped to the shirtfront, and it fitted with a custom-made foam windsock. It certainly didn't help the situation to have the talent speaking quietly either, typically hovering around -15db, which meant the compressor was working overtime to compensate.
I could hear the wind rustle then crackle while I was monitoring through my cans (headphones) and stopped tape to do another take. By now, the wind noise was utterly swamping the speech.
Turning your back
The problem was fixed immediately by having the subject turn their back to the wind, as his body sheltered the mic. Mind you the lighting issue was now another problem, but a quick rejig of reflectors and lights fixed that.
This particular wind problem got me to thinking; what can I do to reduce the wind noise problem on outdoor shoots? I mean to say the radio mic has a foam windsock and the Rode shotgun ,ic not only has a foam shield, but also permanently wears a furry.
I did a net search and found, well, nothing much. There are certainly lots of patent applications for electronic noise reduction systems, but a bare handful on the issue at hand.
Asking mates in the industry proved I had been on the right track for years.
But to me this was an area where I confess I have little knowledge or expertise, despite a childhood spent building electronic gear including mic preamps, mixers and amps and an adult life using them and creating radio adverts.
Danger! Science content
What I did know from basic science was that the microphone element inside the mic was designed to pick up sound waves, and that the movement of air, no matter how gentle would always create sound as it struck any object.
The clue was to have it strike the object as far away from the mic element, and preferably have the resulting sound and energy absorbed instead of being reflected so it could hit the microphone element.
Or to put it in another way, having no moving air next to the microphone.
A quick way of checking this thinking was to stand into the wind, and cover the ears. Deflecting the wind worked. While I have always thought of a foam windsock on a mic as more of protection from physical damage than wind noise, I thought it time to literally bite the bullet and do a test.
Noise, damned noise.
When out and about, I use the Rode shotty with 'full protection' and the on camera mic has its foam cover and furry as well. I use this combo simply because it was an economical system of best practice to reduce noise - but how effective was it?
So I played with the gear- the unprotected shotty versus the foam sock, versus the foam sock AND furry. The answer was a no brainer. The furry combo won hands down for wind noise reduction. My sound gathering for fieldwork was up to scratch.
That was until I had to record an interview in slightly stronger wind conditions where there was no escape. And by slight, I am talking of ten knots on an open plain. Monitoring the sound proved the problem was there, even with a sheltered lavaliere or lapel microphone.
Using the shotty on a boompole as I frequently do was no better. There HAD to be a solution. I had heard of using an enclosed case, nicknamed a Zeppelin due to its shape, but found them to be rare and very very expensive.
In flew the Blimp
I discovered Rode Microphones, an Aussie company, was now producing the Blimp. The Blimp is an enclosed protection device for just this situation - and at the brilliant price under $250 including delivery.
No way was I just going to do a review. I needed this gear as well.
When my order turned up, I assembled the mic into it and decided there was only one thing to do and that was to test it. I headed off to the Echuca Airport where it was blowing 25knots.
(Interested readers may also know that Ben - or 'Biggles' as we call him- is also a qualified pilot. For some reason, a large proportion of Auscam authors are interested in either aircraft or fast cars! Misspent youth? Or not yet grown up? Hard to tell - Ed)
Once there I set up the mic stand next to the camera and pointed things toward the wind - and airport windsock so the wind speed could have a visual reference.
As the camera has two audio channels, track 1 was left to the on board mic, in situ with its foam sock and furry combo to act as a reference, so the audio from the test could be directly compared. Channel 2 was set to the Rode NTG-2 connected via coax for the testing.
A picture tells a thousand words. This screen grab shows the dramatic noise reduction capable by the Blimp, as well as the efficiency of basic noise reduction techniques such as a foam sock and a furry.
Flight testing the Blimp
The Rode would be set under several strict conditions;
- Bare mounted in a Rode suspension mount to isolate it from mechanical noise from the mic stand. It was to have no protection. This was to be the baseline measurement. The mic was set to give a flat response, and not engage the bass rolloff, which is used as a common wind noise reduction technique.
- Still mounted in the suspension frame, it was fitted with just the foam windsock
- As above but with a furry slipped over the foam sock.
- Taken out of the suspension mount, the shotty was placed inside the Rode Blimp following the maker's instructions. The Blimp was mounted on the mic stand so it would be in the same physical space as before.
- Exactly as for the Blimp base test, but with the Rode dead Wombat fur coat placed over the Blimp. (Dead wombat is Rode's name for the furry).
- The results were not that surprising. Even looking at the VU meter on the camera and monitoring through the headphones, it roughly indicated there and then that the wind noise reduction increased to the point of being -30db compared to the on camera mic.
In anyone's language, that is a huge reduction. But it was not until the vision was imported into my NLE, and the sound lines gave an astonishing result. The Blimp with Dead Wombat was giving a flatline.
You can easily see the reduction when looking at the photo.
|Rode 1 level; The first test with a bare mic, the on camera mic level on the left, the Rode on the right.|
- On camera mic -17.3. Foam socked Rode -13.8 A gain of 3.5db. Again an expected result, as the on camera mic has more protection.
- On Camera mic -12.8. Rode with Foam sock AND furry -15. A reduction of 2.8db. I was not expecting this result. I was thinking it would be closer to the on camera mic, as the foam is almost identical and the synthetic fur is from the same roll of material. Mind you, the human ear is just able to distinguish a 3db change, which represents a multiplication factor of two in terms of energy. The Rode was receiving half the noise energy as its on camera counterpart.
- On camera mic -12.2. Rode fitted in Blimp -26.3. A reduction of 14.1db. What can I say? Astonishing.
- On camera mic -9.2db. Blimp in a dead wombat -31.2. A reduction of 22db. This is truly a mind-blowing result and considering the conditions, The Rode Blimp was quite at home.
|Rode 2 level; The second test with the Rode wearing just a foam windsock (right hand number)|
Blimps and foam?
The question did arise; what if the mic wore a foam windsock INSIDE the Blimp? Well, what I was able to find out was that this is not advised, as the higher frequency end would be attenuated, and that as the air inside the Blimp was not moving, the foam sock was a waste.
So how does all this work?
Simply by reducing the energy of the wind and absorbing it before it hits the microphone element! With the Blimp, the outside frame supports a very fine mesh, which stops the wind from passing through, and it also absorbs the energy released. With the dead wombat on top, the long hairs further reduce the velocity of the wind, while also allowing sound to pass through.
|Rode 3 levels; With the Rode wearing a foam sock and a deadrat.|
Any shotty will do; almost.
The other great thing is that Rode have recognized that not all the world has caught on and use their mics, so they provide adapter rings for the double ringed suspension frame to carry mics with a diameter from 21 to 30mm up to 325mm long with the usual three pin XLR connection.
To ensure wind proofing, the Blimp is fitted with a tail cable, so you simply attach your mic cables to the handgrip base. For those who want to mount the Blimp, the standard screw thread is there and fits perfectly on a mic stand or boom pole.
Its also light as well, weighing 755g with the tail cable and no mic, its easy to move and balance. The thing to get used to is that it is big; 490mm long and 125mm in diameter and is supplied not only with the dead wombat, but also a special hairbrush and hex key for customizing the suspension mounts to your microphone.
|Rode 4 levels; The noise attenuation of the Blimp is astonishing at -26db.|
Protect the Blimp
As the Blimp is somewhat fragile, it can't be expected to lie in the back of the car getting battered and bruised. One low cost answer is to buy an aluminum tool case that looks like a briefcase from a super, cheap retail outlet for about $30. Remember the Blimp is 490x125mm in size.
The "grab bag" I use is about 20 years old and it easily takes the Blimp, a set of headphones, the Rode Mic, radio transmitter, spare 20m of coax, windsock and furry and wombat along with spare mic batteries, tapes, cables and Panadol...
While Rode Microphones, an Aussie company is renowned as being one of the leaders in mic technology, it has to be acknowledged that their new Blimp is one of the greatest assets any mic user will benefit from.
Just another test
|Rode 5a levels; But wearing the dead wombat, the Blimp is truly in its element at -31db|
Just moving the bare mic in the shockproof mount showed wind noise. This was astonishing, as I had never really thought about it as a potential problem.
As mentioned before, the noise of the still air striking the metalwork of the moving microphone was creating noise. The issue was fixed simply by placing the foam sock on the mic.
I cranked up the air cooler (it was 42 in the shade outside) and repeated the test. The wind noise was noticeable noise even with the foam sock. This was reduced to a negligible level by slipping on the furry.
Moral of the story; for maximum wind noise reduction on set use a furry inside and a Blimp outside.
What is a furry?
Simply it is a custom-made microphone glove made from acrylic fur.
Some makers call it a dead cat, but being a cat lover the name HAD to change. Rode call their series in order of size, dead kitten, deadcat and dead wombat. Other makers call them fur windjammers, windcutters, fluffies, dead koalas and even roadkill.
The best thing is that you can make a fluffy for yourself, if you have access to a sewing machine or know someone with one.
Simply take the mic with foam windsock fitted, and a sheet of paper. Then trace a pattern on the paper to the shape and size of the furry you need for that mic.
Next head to a fabric shop, and ask the assistant if they have acrylic or synthetic fur and buy a metre. And simply transfer the pattern to the fabric, cut and stitch then fit.
You will be able to get away with at least two furries (one for the shotty, and one for the on camera mic) for about $25.
The next thing you need to get is a hairbrush. One with the long plastic bristles about a centimeter apart is best. Once the furry is on the mic, give it a gentle brush to keep the pile from matting, which would otherwise reduce its performance.
Further information; www.rode.com.au