Wind Noise

Wind Noise: The bane of all motorcyclists that shift up past first gear... If you've ever traveled the speed limit or beyond (who me??), you've wished that wind noise would not trouble you any longer! Well, good news, you can fight back. See the links at the bottom of this short novel for more info, and now let's start with a little primer on how wind noise is created and why technology hasn't really solved the problem just yet.
We ride because we love the wind in our hair, the feeling of freedom it brings, and the joy of being propelled by these marvelous machines we have today. But air has to step out of the way as we pass through it, and because its a fluid, not unlike water, it has to fill in the void created by the fairing.  Unfortunately, that happens very quickly.  The fighter jet pilot does not have to hear the sonic boom made by the aircraft because it can't keep up with the plane, but the void we create on the bike follows us along and wreaks havoc on our ears, clothing, microphones and so on.

When the air collapses back into the void, it does so with a force equal to the atmospheric pressure, generally 14.7 lbs per square inch at sea level. So, imagine three bags of sugar sitting on every square inch of you and your bike and you can see that there's considerable force at play here.

That collapsing 'void' or more properly, 'low pressure area' behind the fairing is like a vacuum to the surrounding 'high pressure' atmosphere and it comes rushing in fast and hard. You've all heard lightening.   That sound is not electricity, it's the sound made when the super-heated air collapses into the low pressure 'tube' that a lightening bolt makes as it heats and expands the air into a low pressure tube (hot air balloon-like) and once the bolt is done, BANG! The air collapses back in on itself, just like the air around your motorcycle does as you pass through.  Is it any wonder we have such a time with buffeting?

Aerodynamics help with this, but few motorcycles are really designed for aerodynamic efficiency.  In fact, most factory touring bikes are akin to pushing a half sheet of plywood down the road at 70mph. 

We can see examples of vehicles that take this wind thing seriously.  Big fairings on Semi's and in some cases 'tail fairings' to ease the high pressure air back together without the turbulence of a quick 'chop-off' like we have behind motorcycle fairings.

We make the fronts of trucks pointy to save gas, but if we made them pointy on the back, the wind buffeting wouldn't happen. Boat-tail cars had this in mind back in the 40's...even tho the execution wasn't perfect. Bottom line, aerodynamics are ugly, expensive and rarely considered when designing motorcycles other than serious competitive racers.  For the touring community, some have it better than others.  The Honda Goldwing, in Ed's personal opinion, is the worst offender and has the least aerodynamic fairing on the market.  The back seat of a Goldwing is only a bit more chaotic and noisy than the front.

Still with me? Good.

So, as you ride, the atmosphere bangs you on the side of the head randomly, and it's not only annoying but can damage your hearing, and play nasty games with your intercom system's microphone. How do we fight back?

1. Put higher pressure behind the windshield. Vents allow higher pressure air streams to enter behind the shield, but too much and you defeat the purpose of unloading your chest and head from the rushing air, and too little and it does no additional benefit.

Two-layer windshields allow a 'curtain' of high pressure air to flow over your head and move the envelope of collapsing air behind you, ideally.  I've personally tried a 2-layer shield, and found it makes things worse in many cases.  Unless you ride behind a shield that is well higher than your helmet, you're probably going to get buffeting bad enough to make riding unappealing.

2. Don't use a windshield. Less wind noise, but now you're fighting to stay upright on the bike at highway speeds. And the rushing air can be amplified by some helmets to a dangerous level.

3. WEAR FOAM EARPLUGS and protect your hearing. Cheap, effective, and easy. We can't stress enough how well this changes the riding experience. May be illegal in some states, so check with your local officials.

When it comes to intercom systems and microphones, you have fewer choices. A live microphone is designed to amplify small sounds, and we place it out there where some very very large sounds to deal with it? First, we tend to want to use a wind screen to diffuse the pressure waves of buffeting, which is the main cause of dissatisfaction with motorcycle intercoms. This is rarely effective since buffeting is not what foam windscreens are designed to deal with.  I've said many times, that foam windscreens are more ornamental than effective on most mics in the market.  The reason is that foam is compliant and the tiny deformations created by wind buffeting pass through the foam to the mic, so in a sense, the windscreen actually carries the sound to the mic.  Foam is good for light wind and to protect against vocal pops and sibilance, but ineffective against buffeting.

Our most effective treatment for mics is to put a second diaphragm on the mic to block the wind's overpressure that make the mics sound like they're being slammed agains the walls, which is techincally correct in the case of the moving diaphragm inside the mic!  That's why your voice signal gets chopped and there's so much noise in the mic during riding.  To do this method, you need to put some heat shrink tubing over the mic and shrink it down so it forms a tight diaphragm over the two sides of the mic.  Doing this allows the cover to vibrate but not move significantly enough to transmit heavy wind buffeting energy to the mic diaphragm. 

We also can tune our intercom to use as little volume or gain as possible to still have communications. Sure, louder or stronger voices are comforting and easy to listen to, but the very amplification used to make them pleasing is amplifying all the noise, and most of that is far more powerful...and to make things worse, the wind noise and speech occupy the same basic frequency ranges, so filtering the wind noise from voice electronically won't ever be effective. Think about it: what is speech but 'crafted wind noise..."??  At EdSets, we use high output mics, which seems like insanity till you consider that using less intercom volume with a hotter mic gives you better signal-to-noise ratio, and better overall performance.

Ok, so what about noise cancelling microphones and active noise canceling electronics? Good question. The facts of life are that noise canceling microphones are not the panacea you we want them to be.This 'technology' is applied by use of a hole on both sides of the diaphragm of a microphone so the ambient (meaning distant) sounds can reach both sides of the mic at the same time and cancel out. Speech or other nearby waves or spikes (like wind buffeting) can easily toss the diaphragm around like a sheet in a hurricane because they are very directional, and not 'ambient' like the sound of a lawnmower on a summer afternoon down the block...that's what the noise cancelling mic can deal with.  That semi in front of you at 70 mph on a windy day?  Forget it.

So, then what about that famous company and their active noise canceling technology, why isn't that part of every headset? Two reasons: it is not effective against the type of noise we deal with on motorcycles, and it's very expensive. Here's the basics: Let's say I add 3 + 3 = 6. Still with me? I hope so! If I add 3 + (-3), however I get Zero! That's the idea behind active noise canceling. Add the 'negative' image of a sound to the original sound, and you cancel them out (read back now on those little holes on both sides of a "noise canceling mic"...same idea... To do this with active electronics we sample the sound, make the electrical 'inverse' of it using a simple inverting amplifier, and then sum them together.  Works great in a coffee shop or on an airplane.  Get a set and try them in your car with windows up.  Wonderful.  Now, roll down one or more windows...Game Over!  The active electronics can't predict buffeting or other random  noises based on past samples, and that's where active noise cancelling headsets fall apart.  Other technologies are needed to cope with our problems on motorcycles.

Even if we had electronics that could do what we want, there are other issues: Headset amplifiers and the small speakers in the helmet can't cooperatively push back hard enough to create a zero-pressure area over your ear when the offending sound wave is coming from the back side of a 70 mph semi trailer or a buffeting blast from the side of your windshield.  Rough calculations say a 150-watt amp and 12" or 15" speakers would do the trick.  We have 150mW (one-thousandth the power needed) and a 1.5" speaker, about a tenth the size we need.

What is EdSets doing about all this?  Innovating.  We're working on a patented new microphone for motorcycle use that is as immune to wind noise as you can get.  Using physics rather than electronics we plan to leapfrog every other technology out there.  We're also working on a new ultra-transparent speaker that delivers sound strong enough to sound natural even through earplugs so that your hearing can be protected while listening to studio quality sound in the helmet, and using communications that are clear, crisp and intelligible no matter the situation.

With all said and done, wind noise is part of motorcycling. If you take the wind out of motorcycles, I'm not sure I want to ride them anymore!  But we CAN live with it.

If you want to read more about hearing protection and how electronic sound canceling techniques lose effectiveness on motorcycles and similar environments, follow these links. Ed has always held that foam earplugs and  properly designed mics are more effective when combined that all the electronics in the world.  You can't cheat physics, but you can use physics to your advantage!

Thanks for reading!

ISVR Research on wind noise and motorcycles...
Hope for Hearing link...

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