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 a couple of weeks ago when on location at a major horse stud filming a tutorial for my client, a major veterinarian firm in northern Victoria. All the talking head pieces had been shot in the stables and then it was outside to shoot a specialist tutorial. Then the wind started to really spring up. Strong wind. Really strong wind.

The talent was around 30 metres from the camera and wearing a radio microphone clipped to the shirtfront and with a custom-made foam windsock. It certainly didn't help the situation to have the talent speaking so quietly either. The levels were typically hovering around -15dB, which meant the compressor was working overtime to compensate. I heard a rustle then crackle while monitoring and stopped tape to do another take but by now the wind noise was swamping the speech.

turning your back

The problem was fixed immediately by having the subject turn his back to the wind so his body sheltered the mic. Mind you, the lighting was now another issue, but reflectors and lights fixed that. (But that's another story) This got me thinking; what could 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 shotty not only has a foam shield, but also permanently wears a dead rat - a synthetic fur coat. I did a net search and found, well.. nothing.

There were certainly lots of patent applications for electronic noise reduction systems, but a bare handful on the issue at hand. 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. I asked (Editor) David to get AUSCAM sound expert Graeme Hague on board.

warning! 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 as possible, and preferably have the resulting sound and energy absorbed instead of being reflected inside so it could hit the microphone element. In other words having nonmoving 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've 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 wind noise

When out and about, I use the Rode shotty with 'full protection' and the on camera mic has its foam cover and dead rat 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 dead rat.

The answer was a no brainer. The dead rat 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. By slight, I'm talking ten knots on an open plain. Monitoring the sound proved the problem was there, even with a sheltered lavalier or lapel microphone. Using the shotty on a boompole as I frequently do was no better.

There had to be a solution. I'd 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 Then Rode Microphones, an Aussie company, announced it was now producing the Blimp.

It's an enclosed protection device for just this situation - and at a price under $250 including delivery. A quick online shopping order with Auscam advertiser VideoGuys of Melbourne saw the box arrive two days later. No way was I just going to do a review. I needed this gear for my own work.

I just grabbed the Blimp and assembled the mic into it and decided there was only one thing to do - test it. So I headed off to the Echuca Airport where it was blowing up to 25 knots and was 42 degrees in the shade. If you're going to do a road test, why not do it under extremes? So I simply 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 one was left to the on-board mic, in situ with its foam sock and dead rat combo to act as a reference, so the audio from the test could be directly compared. Channel two was set to the Rode NTG-2 connected via coax for the testing.

flight testing the blimp

The Rode would be set under several conditions:

1. 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 roll-off, which is used as a common wind noise reduction technique.

2. Still mounted in the suspension frame, it was fitted with just the foam windsock

3. As above but with a dead rat slipped over the foam sock.

4. 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.

5. Exactly as for the Blimp base test, but with the Rode dead Wombat fur coat placed over the Blimp. 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 improved 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 till the vision was imported into my NLE, and the sound lines gave an astonishing result. The Blimp with Dead Wombat was giving a flat line.

auscam online

To say I was impressed is an understatement. I cut a short .WMV (7.5Mb) of the test, and it should be noted that I've done nothing to the audio tracks at all. The NLE was set to its default settings all the way. Even the vision is untouched. This test has to be heard to be believed. It's now on the AusCam website for download. If you do, open it in your NLE to check the audio lines, or play it but pan between left and right very quickly. For the folks who need numbers, the test results were as follows; Bear in mind the wind was around 15 knots and gusting to 20, as can be seen from the airport windsock.

1. On camera mic -10.1dB. Bare Rode -0.1dB A gain of 10dB. This was to be expected. The on camera mic was protected with its foam sock and dead rat that is always in place. The Rode was completely bare.

2. On camera mic -17.3dB. Foam socked Rode -13.8dB - a gain of 3.5dB. Again an expected result, as the on camera mic has more protection.

3. On Camera mic -12.8dB. Rode with Foam sock AND dead rat -15dB. A reduction of 2.2dB. 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.

4. On camera mic -12.2dB. Rode fitted in Blimp -26.3dB. A reduction of 14.1dB. What can I say? Astonishing. 5. On camera mic -9.2dB. Blimp in a dead wombat -31.2dB. A reduction of 22dB. This is truly a mind-blowing result and considering the conditions, the Rode Blimp was quite at home.

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 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.

The bottom line is providing the immediate area around the mic with non-moving air; of dead space. Simple technology, but until now a very expensive one, costing around $900. Yours from Rode resellers for around $250 including freight.

Any shotty will do - almost.

The other great thing is that Rode has recognized that not all the world has caught on and uses its mics. So they provide adapter rings for the double ringed suspension frame to carry mics with a diameter from 21mm to 30mm and 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.

It's also light as well, weighing 755g with the tail cable and no mic it's 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.

just another test

But what about interior work? As a mic is an expensive and fragile piece of equipment, I've always used it - and stored it - with at least the foam sock as shock protection. I did another test, at home with the air-cooling off so the air inside the room was as still as possible.

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 dead rat.

Moral of the story; For maximum wind noise reduction on set use a dead rat inside and a Blimp outside.

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. The low cost answer is to buy an aluminium tool case that looks like a briefcase from a super-cheap retail outlet for about $30. Remember the Blimp is 490x125mm in size.

The case I use is about 20 years old and it easily takes the Blimp, a set of headphones, the Rode Mic, 20m of coax, windsock and dead rat and wombat along with spare mic batteries.

While Rode Microphones, an Aussie company, is renowned as being one of the leaders in mic technology, It has to be acknowledged that its new Blimp is one of the greatest assets any outdoor mic user will benefit from.

The other thing that Rode has to be congratulated on is the cost; Under $250 delivered. The nearest serious competitor was just under $1000.

By Ben Longden

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