KDXRIDER.NET

I was starting to plan some rides for next season and was wanting to ride in some of Missouri's State Parks and came accross this:

Motorized vehicles must be equipped with functioning brakes and muffler, with noise limit not to exceed 86dBA


What is that quiet? I thought 92 was pretty much the standard...

I wonder if their sound test is from a different distance than whatever is the standard for Db tests. That seems awfully stringent. The only way I'm aware of getting a bike that quiet is w/ one of those exhaust snorkel devices. http://www.thedbsnorkel.com/

They tested one on a KTM200EXC in this months Dirt Rider and it went from 92 to 78 Db.

I forget who but someone tried and they don't fit on the KDX.

I reckon I've farted louder than 86db.

KDXer wrote: I reckon I've farted louder than 86db.

Too much information.

Good point. It probably wouldn't fit on the KDX's oem muffler/sa, but it should fit on an aftermarket silencer/sa I would think? I'm not sure what Inda is using on his machine. Boy, what an exhausting subject.

Here's a link to State OHV Regulations... Don't know how up to date it is since they don't have Misouri's new 86 dBA rules on it.

http://www.nohvcc.org/IMAGES/ohvregs.htm

My KDX with a FMF spark arrestor would read that low when tested at enduros. It did better after I repacked it. Repack with 1/2 the string type stuffing in a package of FMF repack material. If remember right, it read 85db.

I wonder why they are using the DbA weighted scale? For reference; A weighting strips the lower and higher frequencies from the sound and only measures those frequencies between 1000 and 4000 Hz. A curve might look like this:

Alright....
I give up!!!!

Why isn't my link showing up as a graphic?

I converted it to a JPG instead.

After writting the following I thought maybe someone would say - what the hell was he thinking??!! FWIW - its part of the importance of knowing where this stuff comes from when we comment on noise/riding/closing area issues. Also some information for self-persevation of one's own hearing - IMO

The weighted dBA scale is set up to measure frequencies between 0-20000 hz. (normal range of hearing for a young healthy human ear.) The frequencies are broken up into specific band widths which are then weighted to mimic the damage response to the human ear.

The human ear can be exposed to intense low frequencies for extended periods of time without suffering long-term permanent damage to a normal person's ability to hear: Intense high frequencies noises for extended periods of time will damage a person's long-term hearing ability much quicker than will low frequency noises.

The "weighting" term (as used in the dBA scale) is a reflection of the human ear's ability to handle noise without suffering long-term effects and was originally based upon national consensus standards developed for a standard 40 hour/5 day work week for workplace noise exposures. Emphasis was to prevent noise exposures which would permanently damage human hearing in the frequency range used for communication (talking).

Since the ear can take more lower frequency noise without damage decibels are subtracted to that portion of the scale (allowable): Since the ear can not take as much sound pressure at higher frequencies decibels are added from the higher frequencies.

Since noise is normal not a pure tone - the various hz bands are weighted when measuring noise on the dBA scale. If you understand the above explanation you also should understand some of the reason 4-strokes seem to be louder - even if their measured dBA is similar to the 2-stroke using the dBA scale. (Hint - they are louder if measured on a sound pressure scale that is not weighted or "dBC scale.

Edit - The chart reflects this weighting but is not the easiest represention to understand that I have seen. I'll look tomorrow for a representation of what happens and try to figure out how to post it on here, if there is any interest.

You cannot generally link to a graphic that is on another site/server unless that site/server's PURPOSE is to do such a thing..sharing pictures. (like imageshack..where KayD put the graphic in question).

Consider about a brazillion people looking at the chart that is hosted/posted at phys.unsw.edu.au, but linked in other places (like kdxrider). Their bandwidth goes through the roof...and nobody is even looking at their site!!

So...such links are generally not allowed...unless you're quite the dough-headed webmaster.

It is also generally considered an unethical thing to do even if you CAN possibly do it. It's theft of bandwidth.

It has nothing to do with it being gif, tif, jpg,or kodachrome.

As far as 86dbA goes, maybe it's the 'A' part of it that makes the difference. Seems much more likely to me that the POINT of the limit is to LIMIT access.

Maybe they can't say, 'NO MOTORIZED VEHICLES'..but they CAN set the noise limit to whatever they want.

In reference to the context of 'Motorized vehicles must...', what were they talking about? In order to get into the park you must meet that standard? Or is it specifically intended for off-highway vehicles?

Well... sounds like it is A weighted... I have never researched it much and my bike has never been tested. It seems like more and more places are doing it or threatening to do it.

It could be that if a bike seems loud they will test it... who knows? The low 86 number may be enough for the braincell challenged riders to just turn and go... hope so!

I just want to be quiet enough to ride anywhere I want.

canyncarvr wrote:
.... Seems much more likely to me that the POINT of the limit is to LIMIT access.

Maybe they can't say, 'NO MOTORIZED VEHICLES'..but they CAN set the noise limit to whatever they want.

CC - I believe you are correct with the above statements. It seems more and more landowners and non-motorized people are expressing their irritation with loud vehicles whether the vehicles are dirt bikes, ATV or snowmachines. This is being reflective in alot of ways - from limiting the number of entries that an motorized event is permitted - to limiting the noise at the property boundaries - to measuring dB levels at the start (and sometimes at the end of an event) to monitor the group adherence to permit requirements - etc..

People are people and we all have different wants, needs, and priorities.

The snowmachiner who is racing a loud machine pass cabins at midnight; the dirt biker who races (dust/dirt/roost) or rides a loud bike past hikers, cyclists, horseback riders; the ATV rider riding down a closed trail or creating their own new trails are hurting the motorized community of riders.

(Even though I'm a motorhead I get pissed when in a parking lot unloading and some Jack Ass will be spinning doughnuts on their machine or just tearing up and down an adjacent hill: It is 100 times more annoying when you can't talk to your friends because the offensive machine is loud!!!)

Indawoods - the dBA scale could be argued to be the best scale to use if we are talking about hearing damage: But it could also be argued to be the worest scale to use if we are talking about noise irritation factors.

86dBA if measured at 20 inches as in a standard enduro type test would have no stock high performance bikes passing the test. I believe 96dBA is currently the general test standard. (With another group pushing for 93dBA at 20 inches limit.)

Another thing to consider is the decibel scale is logrimthic and so a 3 decible change in sound pressure is either halfing the sound pressure level or doubling the SPL depending on which way you are going. So a change from 96dBA to 93dBA is a 50% reduction: 96 to 90dBA is a 75% reduction: 96 to 87dBA is a 87.5% reduction in SPLs. Your 'hearing perception' of the noise does not drop nearly this fast but from the physics perspective this drop in SPL is happening.

Can you type louder!!! I can't hear you!!!

WHAT !?!?!?

KDXer wrote:WHAT !?!?!?

Hey I'm not DEAF!!!!. What did you say???!!!!

I'm thinking it's a typo.... what do you guys think? I'd call them buy not sure if they are open right now...

If I recall 86db was displayed on the STOCK EXHAUST Set-Up...
I would call them, maybe someone typed an 8 instead of a 9....
If not, put your stock on, have it tested and then put the aftermarket on