Stumbled on this
thread/post from skeleton at fz6-sportbikes:
>>>
few weeks ago I experimented with noise abatement for a few hours on a long straight ride.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SPEED
- The following measurements pertain to a stock FZ6, riding with a full face helmet and with the visor sealed, wearing high quality custom moulded ear plugs. Rider is seating in upright posture, with helmet above the wind screen level. Speeds are as read by the speedometer (which is known by gps to over-estimate by 8%).
- The noise level is proportional to the square of the speed (physics).
- The noise level is perceptable as slow as 40 kph.
- The noise level becomes mildly uncomfortable as slow as 60 kph.
- The noise level is tolerable indefinitely at 100 kph (I can ride for hours here).
- The noise level is very uncomfortable at 120 kph. (I can bearly hear myself talk.)
- The noise level is painful and eventually causing harm at 140 kph.
- The noise level is intensely painful and unbearable at 160 kph. (I can bearly hear myself scream.)
- Conclusion:
Long distance riding is only sustainable below 120 kph, and 100 kph is ideal.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ EARPLUGS
- I have tried the following ear plugs. The following data lists their audible attenuation rating; this is consistent with my own perception. (Note -3 dBA is perceived by human ear to be half the noise level - this is very noticeable.)
20 dBA = Conventional mp3 music ear phones (Sony).
24 dBA = Moulded mp3 music ear phones (Klipsch).
28 dBA = Conventional cylindrical shaped plugs.
33 dBA = E-A-Rsoft FX earplugs (bell shaped plugs).
36 dBA = Custom moulded silicone ear plugs ($100 pair).
- Conclusion:
Music ear phones should be used only for limited time period and at lower speeds.
Earplugs are essential and custom moulded silicone is the best.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELMET
- I rode with a borrowed Arai non-flip helmet to compare it with my flip-up helmet. I could not perceive any significant difference in the sound attenuation.
- I wear mostly a Shoei Multitec (flip up) helmet. This is a very good helmet as far as flip-up types go.
The underside of the chin is open, which allows air turbulence to occur and make noise.
If I plug the underside with a rag, then the noise appreciably diminishes (but no one would ride that way).
- I also have a BMW System-6 (flip up); this is slightly better than the Shoei but more expensive.
The underside of the chin is sealed with a body fitting foam section. This precludes any air turbulence.
This feature seems to be why the BMW helmet is quieter than the Shoei.
- I have added a small strip of soft foam against the inside edge of the helmet at the ear cavity. This foam will then contact with my ear plugs and maintain a constant pressure against them - essentially pushing them in and sealing them to the skin of my ear. This significantly increases the noise attenuation of the earplugs; however the added pressure eventually causes discomfort to the soft tissues of the outer ear.
- I have experimented with taping over all the seams and joints of the Shoei helmet - even the visor. This resulted in a helmet more sealed and aerodynamic than non-flip helmets. Regardless, this taping had virtually no benefit to sound attenuation.
- I have ridden momentarily with my hands in front of my helmet to block the wind flow. There were two positions where my hands obstructed wind flow sufficiently to reduce the noise: 1) both hands fully in front of the helmet about a foot away and completely obsuring my vision - this functioned equivalently as a blind wind screen, and 2) one hand beside and in front of my ear but sticking outwards, akin to Dumbo the Elephants outstretched ears - this functioned to move the boundary layer away from the side of the helmet.
- Conclusion:
Flip-up helmets are not appreciably louder than non-flip helmets.
A tight fitting helmet is much quieter than a loose one as it helps to seal the ear chamber.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ WIND SCREEN
- I have a stock screen on my FZ6; I have not experimented with any others. Instead, I have experimented with my helmet position with respect to the screen.
- The air flow streams off the edge of the screen essentially horizontal, regardless of vehicle speed, and regardless of location around the radius of the screen. Thus, air flow does not continue on the same geometric path as defined by the slope of the wind screen. Once it reaches the top of the screen, it transitions to a horizontal trajectory almost instantly past the trailing edge.
- The human ear is about level with our eyes. The boundary layer of air (where turbulence starts) streaming back from the screen can be kept above the ear by merely alligning one's eyesight at or just below the top edge of the wind screen. For the FZ6, this requires me to lay my chest upon the tank, with my head and neck cranked back. (I'm in good shape, for which my body can tolerate this posture for a few hours with little discomfort. I would image many riders would find this very uncomfortable. Regardless, I will lay on the tank solely to relieve the strain on my ears.)
- Try this: ride with helmet above the wind screen level and note the high sound level. Now, duck down with helmet below the wind screen and note the sound level is only marginally lower. This is because allot of noise is created *AT* the small wind screen of the FZ6; then it propogates to the rider's ear, regardless of him ducking under the wind screen. Additional noise is created as it eddies about the front of the bike which has minimal fairing. Contrast this with riding a full sized touring bike with its large and continuous body fairing and tall and wide wind screen. The touring bike causes much less eddies and turbulent air flow as it rides into the wind compared to the sport bike design of the FZ6. I test rode a Honda ST1300 with its wind screen placed in the lower position, and I sat up to position my helmet above the boundary layer. That ride was no louder than me riding the FZ6 with my helmet under the boundary layer.
- Conclusion:
Placing helmet at eyesight level (or lower) to the top edge of wind screen is adequate to be below the boundary layer.
A larger (tall and wide) wind screen is significantly better than tall and narrow.
A wider body fairing is significantly better than little or no fairing.
Placing a tall screen on the FZ6 is not sufficient to compete with the quietness of the broader fairing and wind screen of a full touring bike.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ENGINE NOISE
- Try this: park the bike, put it in neutral, then rev the engine to 7000 or 8000 rpms. It is screaming in your ear, right? Well that same sound level is arriving at the rider at full highway speeds. But is this the primary source of noise? Nope!
- Don't try this but I did: park the bike on center stand, put it into 6th gear, and rev the engine to 7000 or 8000 rpms. Notice the sound that additionally comes from the running drive chain. Most is from the engine but the chain does add an appreciable level of noise.
- I rode at 130 kph, noticed the noise level, then quickly pulled in the clutch and let the engine wind down to 1300 rpms. Surprise: the loud noise level is almost unchanged! That's because most of the noise is not coming from the engine, despite it screaming loud level. Note, the chain is still spinning of course.
- We all know tires rolling on the road make impact noise. This is actually significant. Slick tires are quieter than treaded tires, and narrower ones are quieter than fat ones.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ BIKE COMPARISON
- I did some subjective measurements of noise level on the FZ6, and compared it with the BMW K1300GT. For noise attenuation, most full-sized touring bikes should be essentially similar, as their screen, body fairing and engine displacement are similar.
- This analysis serves to question:
1) What is the reduced noise level of a touring bike compared to a sport-touring bike?
2) What is the required reduced riding speed on the FZ6 to yield the same noise level on a full touring bike?
- Conclusion:
A full touring bike produces about 30% of the noise level as a sport-touring bike to the rider's ear.
A full touring bike can travel at double the speed of a sport-touring bike to yield the same noise level.
<<<
I, myself, was bothered during the ride (4-5 hours) today (err.... yesterday) by wind noise. I have been using these
earplugs with Shoei RF1100. And thought they were the best (most noise reduction) of the ear plugs that I could find in local stores.... I will definitely be looking for substitutes...
