Sound Off

No doubt you've heard the saying "There is a fine line between love and hate." What is just as true, but less often considered, in the motorized world is "There is a fine line between sound and noise." And actually, the comparison is even more prophetic, as most people love sounds and hate noise. So the real question is, where does sound end and noise begin?

Sound is defined in Webster's dictionary as "mechanical radiant energy that is transmitted by longitudinal pressure waves in a material medium (as air) and is the objective cause of hearing." Noise is defined as "a sound that lacks agreeable musical quality or is noticeably unpleasant." According to the recently passed California Assembly Bill 2274, effective January 1, 2003, "All off-road vehicles must meet the static noise test limit of 96 decibels to legally use any and all public off-road riding areas." This standard is a reduction from 99 decibels and applies to all EPA-legal bikes manufactured since January 1, 1986, and all competition bikes made since January 1, 1998. To keep this from being another toothless law, California authorities purchased enough of the new QUEST sound meters at a cost of $1400 each to equip the rangers in the field so they can actually enforce the limit.

As it stands, it is really simple to understand. If you want to hear the pleasant sound of your machine running in California, then its sound must be 96 decibels or less in the static test. If your bike makes more than 96 decibels, it's too noisy and won't be allowed on public lands. But for those of you in states with more/less stringent requirements, remember, what happens in California tends to work its way eastward. This is not a regional issue, but a national one that off-road riders must accept.

So we incorporated the same 20-inch stationary test that you could receive from a USFS ranger into our 24-Hour test. Like your friendly ranger, we did our testing on the machines per the Motorcycle Industry Council (MIC) and Society of Automotive Engineers (SAE) J1287 July 1998 stationary test at both the beginning and end of the 24-hour period. In addition, we monitored sound levels in the field, measuring from 50 feet away to alongside the bikes--as per the 82-decibel EPA test, which is a second-gear full-throttle acceleration test that all EPA-legal motorcycles must pass. We weren't scientifically rigorous about this test for two reasons. First, this isn't a practical test for off-road machines in the field and thus isn't used by any authorities for sound enforcement. And second, we were only interested in the subjective comparison of the 24-Hour test bikes and other machines, including the noncomplying ones, out on the trails.

To add veracity to our testing (not that we can't be trusted), we had the static testing done by volunteers from the BlueRibbon Coalition and U.S. Forest Service rangers, using their equipment and following the guidelines printed by the MIC each year which lists the procedures and test rpm for all models. This is where things get a little bit dicey. Originally, the official test procedure and guidelines were developed before adjustable power valves on two-stroke engines and before multivalve, high-lift, high-rpm four-stroke engines existed. The SAE J1287 specifies the test rpm used is half the maximum rated rpm stated by the manufacturer. We encountered two basic problems just in our testing at the 24-Hour.

The first is the delay in information gathering, printing and distributing to the authorities. The MIC distributes the official pamphlet each April with the test rpm supplied by the manufacturers. This means for our test done the first week of February, and basically for the first five months of each calendar year, the authorities monitoring the noise levels don't have current information on new models. In fact, we didn't have the test specifications for the new Yamaha WR250F and WR450F and the Gas Gas EC-250 and FSE-450 (ours was the first in the country). What this means to you is the difference between riding and not riding. So be prepared and gather the specifications from your owner's manual or dealer to verify the proper rpm your machine is supposed to be tested at and keep the paperwork in your truck or fanny pack.

Second, we discovered as little as 50 rpm can greatly sway sound levels. Just halving the maximum rpm for bikes without information in the MIC handbook can really throw off the data gained in the test. The specified test rpm on most of the modern adjustable-power-valved two-strokes tends to be close to the rpm when the valve opens, drastically increasing the noise level. Four-strokes experience a similar problem, but this time with carburetor settings. A carb that's too lean or too rich can cause difficulty in maintaining the proper test rpm, which can then induce erroneously high noise levels during the test.

The good news is our testing revealed that all 11 bikes made it under the 96-decibel limit. The surprise was that, after 24 hours, most machines actually tested lower. This could have been the result of carbon buildup on the inside of the pipes, deadening of the noise or rich conditions caused by dirty air filters. But the bottom line for you is that all bikes still passed after a full day of hard riding.

Our unscientific 50-foot drive-by test also impressed us, demonstrating the disparity in noise levels between the test machines and other bikes equipped with motocross-style (closed-course) silencers. The loudest bike we observed was a 450 exhaling through an aftermarket closed-course system at 106 decibels. What should be noted is that's 106 decibels at 50 feet away; up close your ears would be ringing from the roar. Since this was not a completely scientific, regimented test under a controlled environment, we had bikes pass by at half to full throttle. Naturally, this affects the decibel levels, but the overall data we obtained does represent a good cross section of actual trail usage and associated sound radiation.

The trailside sound test gives the perspective the general public gets as we whiz by them. And it points a finger at excessively deafening bikes with motocross mufflers on the trails--not machines equipped with proper silencers--as a strong instigator of the language in California's AB2274, which reduced the acceptable limit to 96 decibels. This is an extremely important point.

Back in the early '70s, the slogan was "less sound = more ground." A lot of effort went into getting noise under control and progress was made, especially with the advent of water-cooled engines. So it was checked off our lists and forgotten. But that's the problem: The general population didn't forget and now our neglect is biting us in the butt.

Personally, I will not trail ride with a loud four-stroke sporting a closed-course silencer. Those things hurt my ears and, undoubtedly, will lead to closure of trails and possibly motocross tracks I want to ride. A side effect of our formal 24-Hour testing revealed that off-road-approved bikes in our test not only meet the noise requirements of the general population but are fast and fun as well. These are the kind of bikes we need to be riding if we want to hear the pleasing sound of our engines on the trails in the future.

We also invited the aftermarket exhaust companies to bring any systems they felt were quiet, then ran them through the sound gauntlet and a quick ride test. Here is what we found:

Standard Quiet:

Sean Finley: The CRF held on to its traditionally smooth easy-to-ride power and had great response in the low-end. The bike lost a small percentage of overall power but still had enough grunt for the track and trails.

Bill Keefe: The Big Gun system delivered a strong responsive hit of power off the bottom and worked great on the trail. This relatively quiet system offered plenty of power and was still fun to ride.

Tip Insert:

SF: Once we installed the smaller tip, I noticed very little difference in engine performance, but the bike was very quiet while I was riding.

BK: As expected, the performance took a slight nosedive feeling flatter across the board. The response was predictable, smooth and easy to ride. Even with a slight loss of power, the Big Gun exhaust still felt very alive for being so muted.

Glen Sizemore: The Q had more bottom than stock but was still smooth throughout. Quiet with easy-to-manage power, yet not boring to ride.

SF: The E-Series has great power that was close to stock but more responsive off the bottom. I liked this system on both the motocross track and trail.

John Lovett Jr.: The E-Series maintained the smooth linear power delivery but was more torquey than the stock unit. The biggest gain I noticed was off the bottom the power was very responsive.

George Lamonte: The E-Series lacked the roll-on the stock unit has but has an explosive mid that pulls hard into the top-end. I liked this unit for both MX and off-road.

JL: With the E-Series mounted up to last year's YZ426F the power was much smoother than stock. The Yamaha lost the big hit in the mid and was not as torquey.

GL: The E-Series made good power throughout the entire powerband. It was explosive when you really get on it and had decent overrev.

No Insert:

BK: With no sound baffle in, the Yoshimura system delivered better roll-on off the bottom and pulled harder throughout the entire powerband. The motocross setup was a 10 on both the track and the trail for me.

Mid Insert:

BK: After inserting the quiet tip, the power felt muffled and less responsive. The loss of power was more noticeable on the motocross track than when out on the trail. This system still provided adequate power to tackle anything on the trail or motocross track.

SF: The Yosh system gave a smooth power delivery through the entire power range. This system was so quiet I could hear engine noise.

Small Insert:

BK: The power really begins to fall off with the smallest tip inserted. This tip is not recommended for the motocross track. On the trail, the power stumbles when you snap the throttle; the bike doesn't make power until you build up revs. The subdued tip made shifting out of the question, but if you require a very quiet exhaust, this would do the trick.

SF: Once we installed the small tip, I noticed an inconsistent hesitation in the powerband. It was still smooth most of the time and very quiet on the trail.