Editor’s Note: This article was contributed by Guido van Eijsden, developer of Scenic, a highly rated Motorcycle Touring app for iOS. 

Make no mistake. At highway speeds, wind noise in a helmet WILL cause permanent hearing loss if you don’t protect your ears properly!

In this article, I take a deep dive, through science and experiences, into what exactly causes the noise and how it can be reduced by modifications to your motorcycle, your gear and hearing protection.

The creeping danger

First a bit of science. Long or repeated exposure to sounds at or above 85 decibels can cause hearing loss (source). Sound levels in a motorcycle helmet can reach up to 115 decibels or even more. To humans, a 10 decibel increase is perceived as a doubling in loudness. So 115 decibels sounds 8 times (3 times doubled) as loud as the threshold where hearing loss can occur. For reference, an MP3 player at full loudness produces 105 decibels.

Hearing loss is a combination of the loudness of a sound and the time you are exposed to that sound. The shorter the time, the louder the sound can be before hearing loss occurs. The longer the time, the quieter a sound needs to be to prevent hearing loss. Typically, on a motorcycle, we ride for a long time, often at high speeds. And the higher the speed, the louder the helmet noise. From a hearing loss perspective, that’s the worst combination!

So, on a motorcycle at highway speeds, where we are exposed to loud sounds for a long period of time, helmet noise can be extremely dangerous. Not only can it permanently damage our hearing, it also causes fatigue. I’ve done full day rides, without good hearing protection, being exhausted at the end of the day. It’s no fun and fatigue can be a danger in itself, reducing attention to the operation of your motorcycle and the traffic around you.

Hearing loss is not noticed instantly. It’s a creeping danger. Have you ever been to a club, bar or concert where the music is very loud… where the evening or the day after your ears are still ‘ringing’? That ringing is called tinnitus. While tinnitus is not a sign of hearing loss, prolonged exposure to loud sounds is the most common cause of tinnitus (source). Most of the time, the hearing loss goes in small increments, not noticeable to you. Again, it’s a creeping danger. Over time, however, these small increments can add up, possibly leaving you needing a hearing aid as you get older. In an old 2004 study it was concluded that 6% of riding instructors and a whopping 40% of professional motorcycle racers suffer hearing loss (source).

The cause of Helmet Noise

Not surprisingly, helmet noise is caused by wind. Most importantly the riding wind, but also side winds can have an effect. Because we can’t change the wind caused by mother nature, I’ll focus on riding wind here. Obviously, the faster we go, the faster the riding wind hits our motorcycle and helmet, and the louder the noise in our helmet becomes.

It’s not only our speed that determines the noise level though. It’s the flow and direction of the wind too. In fact, I found that, the flow and direction of the wind has more influence on the noise level than my speed. With flow I mean how clean the airflow is when it hits your helmet. And with clean I mean an uninterrupted constant flow of air, the opposite of turbulent airflow. As an example… when you ride on the highway with no other traffic around, the air hitting your motorcycle is clean, but when you are riding closely behind or next to a truck, the air becomes turbulent. You can feel this as your motorcycle becomes less stable.

Now, a clean airflow around your motorcycle does not mean a clean airflow on your helmet. To put it simply, where your motorcycle is, there can be no air. As your motorcycle moves through the air, it displaces the air. The air has to get out of the way and return again as your motorcycle moves forward. This constant displacement of the air causes turbulence. The amount of turbulence is highly determined by the shape of an object moving through the air. The best shape that causes the least amount of turbulence, is the shape of a raindrop. That’s why most professional racing bikes try to mimic this shape as much as possible. In other words, they try to make the motorcycle as aerodynamic as possible. In general, however, our motorcycles are far from that shape, so turbulence is just something we have to live with.

If we would form one solid shape with our motorcycle we would only experience turbulence behind us, but on all motorcycles with a screen, there is a gap between the screen and where our helmet is. Above image shows very clearly that the turbulent air (blue lines) are mostly behind the rider and between the windscreen and the rider. Also note the turbulent air coming from below, behind the screen.

High-speed air flows over our screen creating a sort of vacuum just behind our screen. Other air, from other sides and below, tries to fill that vacuum, creating turbulent air behind our screen. And that’s usually where our helmet is so that turbulent air hits our helmet from all sides. Below picture shows this in a simplified way.

The below picture shows another situation. The screen is not as high as in the above picture. It causes less turbulence, but all the airflow over the screen is concentrated, hitting our helmet head on. Also not an ideal situation.

Buffeting

Buffeting is a special, extremely unpleasant, kind of turbulence. The airflow hits our helmet in such a resonating frequency and with such force that it causes a very low droning sound. It can even be so strong that it shakes/vibrates our helmet, sometimes even blurring our vision.

Factors influencing Helmet Noise

If you’ve ridden different motorcycles for a longer period of time, you know there can be many causes for helmet noise. A lot of factors come into play. From my research and experience I found that all below factors can influence helmet noise. Some have more influence than others. If I had to take an educated guess, this is the order in which they influence helmet noise, ordered from most influential to least influential.

  • Our windscreen (height, width and angle of the screen)
  • Rider position (position and angle of our helmet)
  • Our helmet
  • Use of a scarf, balaclava or helmet skirt
  • The motorcycle (fairing) design

The motorcycle windscreen

I’ll handle this together with rider position as they are heavily intertwined. One can get quite scientific about this, so I will 🙂 In this research paper helmet noise was measured for different windscreen heights, different speeds, different windscreen angles and different helmet angles (emulating different riding positions). Here’s a picture of the setup they used.

They measured in a wind tunnel, under strictly regulated conditions, eliminating all other factors that can influence helmet noise. As a screen, they used a square plate, so not exactly a normal motorcycle screen form or shape, so keep that in mind. Here’s a conceptual drawing of the setup they used.

The results in the report are a bit difficult to interpret, so I transformed the key results to the below 4 bar charts. Each chart gives the result for a different speed and helmet angle (rider position) combination, while the bars vary the screen angle and screen height. Screen height is measured as the distance from the top of the screen relative to where the ears would be in a helmet (h in the above drawing). The base of the screen was positioned 30cm away from the center of the helmet (x in the above drawing), except for the most right bar, where it had to be positioned a lot further away (84cm), to achieve the angle and the screen height.

Now, I’m taking these absolute results with a grain of salt, because this was a very ‘synthetic’ situation. The difference between the results is what I’m most interested in. With this in mind, a couple of things are noticeable:

  • Speed makes a huge difference. In all cases, the doubling of the speed from 40 km/h (25 mph) to 80 km/h (50mph) caused at least a 10 decibel increase. As discussed above, to the human ear, this is felt like doubling the noise.
  • Without windscreen is the quietest in almost all scenarios, except the two at low speed with the screen at the same height as the ears. Although even in these two scenarios the difference is small.
  • With an upright riding position, with an angled screen, the sound level increases for higher screens. With a straight screen however, the sound level decreases as the screen gets higher.

So, what’s the best screen height and angle? Well, going by these results it’s as simple as adding up the values of the same colored bars. This results in no screen being the best with a score of 423, followed by a score of 428 for the straight screen at ear height.

We can do a bit better than that though. Typically our riding position is fixed. According to this study, if your bike has a straight up riding position you are best of without windscreen, followed by the same straight screen at ear height. However, if you have a forward position on the bike it’s a three-way draw between no windscreen, the 40 degree angled screen at ear height and the straight screen at ear height.

We can even go a bit further than that. As sound levels at low speeds are lower, thus less damaging to our ears, and we as motorcyclists typically ride fast, one could argue that the high speed values should way more when picking ‘the best’ setup. Actually, this does not make much of a difference. Still, no screen comes out as a winner, followed by the straight screen at ear height.

There’s one important thing to note. Test results for the straight screen 15cm above ear height are missing (because the screen started vibrating excessively). It might be that this screen setup would actually perform similarly or perhaps even better than no screen. Alas, we can’t be sure without the data, although the one reading we do have seems to suggest this.

My personal interpretation from all of this: GO TINY/without or GO HUGE! Why do I say this? Because that’s also my experience from the 6 bikes I’ve owned so far. The only bike I truly enjoyed riding long stretches of highway on, was my BMW R1200RT. It has a huge screen which is electronically adjustable. On the highway I always had it in the top position, reaching well over my head. After this, my Buell 1125CR (naked), BMW R1150 Rockster (naked) and my Yamaha XJ600S (removed screen), were the most enjoyable on the highway. Next to this I owned a Honda Interceptor and currently I own a Yamaha FJ09 / MT09 Tracer. Both have a medium screen and both are exhausting to ride long stretches of highway on.

Helmets, Scarfs / Balaclavas & Helmet Skirts

As our friends at WebBikeWorld stated:

It is our considered opinion, based on many years of evaluating dozens of different motorcycle helmets of all types and talking to experts in the field that there are basically only two types of motorcycle helmets: loud and louder.

Motorcycle Helmet Noise – by WebBikeWorld

So helmets are noisy. We all know that. But there is a huge difference between full-face helmets and open-face helmets. I won’t even discuss open-face helmets here. They are definitely in the “louder” category.

The full face and modular helmets cover your whole face and have a chin guard. This is not only better from a safety perspective, but especially the chin part helps a lot in reducing noise. In short, they reduce the amount of air that can enter in your helmet. And that is essential to reducing helmet noise. Typically, the more air entering your helmet the noisier it gets.

Air enters in your helmet by vent holes, through your visor (even if closed) and at the bottom hole: you know, the part where your neck sticks out. This last part is especially important, because, as mentioned above, directly under the helmet is usually also the area where a lot of turbulent air is.

Some helmet manufacturers pay special attention to noise reduction. Shoei and Schuberth are good examples of this. They test their helmets in wind tunnels and design the outer shell accordingly. Also they pay special attention to the inner liner and the neck role, to keep as much air out as possible. I own a Schuberth and it’s very quiet indeed. But I found it’s only very quiet in CLEAN AIRFLOW. When turbulence is involved it becomes loud. I dare to say as loud as any other helmet.

In order to prevent air entering the helmet from below, a lot of riders use scarfs and balaclavas. In my personal experience, this helps a lot, especially thicker scarfs and even a thick collar on my jacket helps reduce the helmet noise a lot. Another way to reduce air entering from below is the use of a helmet skirt, like the WindJammer or the NOJ Quiet Rider. They all help keep the air out thus reducing helmet noise. However, in warmer weather, this might not be the way to go. Reviews of the windjammer as well as the quiet rider report on their helmet fogging up when installed.

Motorcycle (fairing) design

As mentioned above, riding with a screen creates a vacuum behind the screen and air will come in from below and sideways to fill up that vacuum, causing turbulence and sometimes even buffeting. Mostly, it’s relatively easy to check if this is happening for you. Just hold one of your hands around the tank area and around the dashboard and screen, to see if it gets any better. This video by MCRider explains how to do this.

For most motorcycles ‘air deflectors’ are available that guide the airflow to a different direction. They mount on different parts of the frame or fairing, depending on your bike and the area where you want to deflect the air.

Conclusion

All the above factors can make a lot of difference in reducing helmet noise. The windscreen on your motorcycle is by far the biggest factor in this. So, start there (and remember… go tiny or go huge) and once you find the best setup for you and are still experiencing excessive helmet noise, start looking at your helmet. Get a good, quality build helmet, with a good visor seal, a well designed aerodynamic shell and well-designed vent holes. And, if you’re riding in a colder climate, add a scarf, a thick balaclava or a helmet skirt. If that is still not enough start looking at air coming up from below and from the sides of your frame/fairing and see if that can be resolved with air deflectors.

Last, but certainly not least, wear earplugs! Even if you achieve the most ideal setup for you, earplugs are a necessity if you ride motorcycle. There are many kinds, from those cheap orange disposable earplugs, to special motorcycle earplugs filtering out only certain frequencies, to top of the line custom molded earplugs that fit your ear perfectly. It depends on your budget and what you’re comfortable with, but just ware something. Especially on those long stretches of highway.

Ride safe and enjoy the ride!

 

Featured Image: XC Engineering srl

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