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Shhhhhhhhh!...let's keep it down out there!

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#1
Let me get this outta the way right now. I like the sound of a fire-breathing thumper with the throttle pinned WFO. But I, along with everyone who shares my likes had better start doing they're part to reverse this trend of un-godly loud aftermarket exhaust systems and get used to quieter systems.

Go to www.motorcycledaily.com for some insight on this topic and how it relates to the publics perception of us.

Db's are going to be more important to me than h.p.'s while shopping for my next system.

Thump on!
 
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#2
So......how offensive would you say 97dB is? Thats what my Big Gun system tested out at in the dunes this weekend.

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#3
97db? Thats pretty loud. To me though, thats just about right...no earplugs needed.

However, if we want to keep riding areas open, we have to be more concerned with what the opponents consider offensive. I'm gonna aim for 92 dbs or less. Stroker has a turndowned insert for my WR250 muffler but doesn't state how much reduction it provides. I dropped em' an email to find out yesterday. I will let ya know how it goes.

The FMF powerbomb with the stock muffler is supposed to suppress a little also and if they're h.p. claims are accurate, I may try one.

Thump on!

[This message has been edited by Buckwheat816 (edited 02-28-2001).]
 

Neil Wig

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#4
Keep in mind that dB measurements are a logarithmic scale. This means that for every gain of 6 dB, the sound energy doubles. So, 97 dB is almost 1/2 the sound energy of 100 dB. I don't have any test data to back this up, but I would suspect the sound energy to be the driving factor when considering how far the sound will travel (and how many people will be bothered by that sound). So, when you see a "modest" increase in sound level of 2 or 3 dB, it is equivelant to 30% to 50% more sound energy.

Later
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#5
Neil is right. The db reading can be misleading, and it doesn't address frequency. Peoples annoyance level has as much to do with the frequency of sounds as it does with amplitude/volume. So db is just part of the problem

As an example of Neil's point, OSHA provides a list of how long you can expose your ears to a specific volume before damage occurs.

90 dB A 8 hrs.
95 dB A 4 hrs.
100 dB A 2 hrs.
105 db A 1 hr.
110 db A 30 min.
115 dB A 15 min.
120 dB A HUHHH?????????????
 
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Jonala

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#6
Buckwheat,

I've been doing experiments on a 2001 XR 250. I've made custom inserts that fit into the tail section to the muffler.

My results showed that a insert that had a down turned pipe made no difference on my dB meter. The bike did "sound" quieter. I was surpised with that result.

I would be interested in seeing what response you get from Stroker.
 

BadgerMan

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#7
That’s a true story.

I have done testing of small electric motors in a sound proof environment and you can have two motors that both pass the max db spec but they will sound very different and one may even sound substantially “louder”. You have to do an analysis of the entire frequency spectrum to get the true picture. I don’t know much about db meters but IMO, they are a fairly crude measurement tool with a high R&R percentage. I do know (based on experience with different bikes) that four strokes are easier to get through an enduro sound check. I have heard two theories on this:

1. Older guys, like me, run sound checks and they like the sound of four strokes! LOL!
2. Db meters are “more forgiving” of the frequencies that four strokes typically emit.

I am not sure which to believe but I do know that sound pressure levels of varying or mixed frequency are tough to accurately measure in a repeatable manner.
 

Vic

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#8
It would seem that the real solution to this problem would come from noise cancellation technology. Does anyone know enough about this to comment on whether or not it could be feasibly applied to dirt bikes?
 
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#9
A paved, oval racetrack sits abandoned with pine trees growing through the track, infield, and metal bleachers less than a mile from my house. The track ended up in the city limits due to annexation. While the city council could find no legal means to shut down the track, the community petitioned them to shut down the track, primarily because of noise complaints. A resolution was passed prohibiting the sale of alcoholic beverages which apparently made the track unprofitable and it has never re-opened.
If you will notice from my address, this occured in the deep south. If the people down here will not tolerate this type of noise, the rest of you in other parts of the country haven't got a prayer.
If you can run a load exhaust only on private land and change to the stock exhaust when on more sensitive riding areas, I commend you on your behavior. In my experience, riders tend to lose patience with changing the exhaust, and the loud one is usually left on the bike.
Dirt bike riders are an extremely small percentage of the population; the rest care very little of our effort to perserve off-road riding. We can jump up and down screaming about out rights to make noise. Just as your right to freely swing your arms and fists ends at my nose; our right to make noise ends at someone's eardrum.
I am astounded that some dirt bike riders are so politically naive that they cannot understand the other 99% of the voting population and what our less than 1% has to lose.
 

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#10
Well obviously I'm not a sound engineer but I think part of the problem is with the nature of the sound being emitted by our thumpers compared to the two strokes.

Folks are saying the new thumpers are too loud (they are) as opposed to 2-strokes (also too loud).

The lower frequency (longer wave) tone of the thumpers tends to be "omni-dircetional" it's as much "felt" as "heard" this is why you can place your subwoofer anywhere in your surround sound system.

But the higher frequency (shorter wave) "center channel" sounds (like a two stroke) need to be placed at ear level for optimum performance.

When your in the woods you can hear the big four strokes coming or going because the sound waves are more spread out, as opposed to the more linear two stroke soundwaves.

The pipe guys have to do something. or we all lose. we need to stop this "I won't give up 2 hp or 1 lbs of weight" and the "they better not mess with my closed course pipe!" mentality. The truth is as long as the "closed course pipes" are available, John Q. Biker is going to put them on their trail bike and ride it on public lands.

Tis better to ride with loss, than to not ride at all.

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#11
I think that a noise cancellation system would be unfeasable for bikes. The systems I saw on an automotive show were very complex and took into account the shape and volume of the cabin as well as passenger head position. It was very precise stuff and only intended to pacify occupants of the vehicle...not bystanders.

I do think that there is much to be learned and applied from the automotive applications as far as sound wave manipulation goes. The systems for bikes only seem to absorb sound (most, very little). DynoMax and a few other performance muffler makers have made great advances in quieter systems by just incorporating tuned fins, dams, or whatever within the muffler that still allow for flow that is near straight-through designs. This is the technology that I think the motorcycle guys need to be copying.

Thump on!
 
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#12
While I agree with notion of keeping the bikes quiet, where does it end. If 95db. is O.K. then the next time it will be pushed to 90db. and so on until mouse flatulence drowns us out. The gun lobby understands this and fights all legislation tooth and nail. Once you let the 'do gooders' dictate any regulations it won't stop there. Not everyone has to be happy with what everyone else does. To rob a Liberal ideal "share the misery." Simple fact is the people complaining about the noise don't want it modified they want it eliminated.
 
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#13
Posted by Jonala

*My results showed that a insert that had a down turned pipe made no difference on my dB meter. The bike did "sound" quieter. I was surpised with that result.*

The reason it sounded quieter with the turned down tip even though the actual decible level was the same is because the sound was being directed towards the ground, where some of the sound energy was absorbed.
 

steve125

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#14
I'm getting rid of my DSP exhaust for the 250f. It shares the same can as the FMF. From a performance standpoint they deserve a pat on the back. But to mass produce a muffler(105db)thats this annoyingly loud, they could use a swift kick in the butt!
 
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#15
It saddens me to say this....

You can make your bike as quiet as you want. I love the noise my 650 makes. I also ride in Nevada. I see 1 person in a 10 day trip in the hills, if I am lucky. That person is usually a cattle rancher off in the distance.

I agree with keeping you bike as quiet as you can. BUT, if most of Glamis can be closed because of a FLOWER, the public has gone completely NUTS. These are all excuses to ban off road vehicles.

It won't matter if we are off-roading on a silent invisible hovercraft. Someone will make up something about the impact to the pigmy shrew's feeding source. It's all a bunch of S%$T.

It's going that way with guns and your car is next. Visit Kalifornia. This place is pathetic.

Lastly, all of these saviors of the land-WHERE ARE THEY? I have spent a great amount of time outside and I have yet to see a tree-hugger(except on t.v.) These people are not even in the back country.

I loved life a lot more when I was a kid and was ignorant of how things work. If you ride a dirt bike, your government is out to get you. It's only a matter of time.



KDK
 

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