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The decibel limit for the 2007 racing season is 99-decibels. While racing in ATVA-sanctioned events last year, pro riders were required to comply with a 102-decibel limit as measured using the Society of Automotive Engineers J-1287 test standard. The test is performed with a sound meter on the "A" scale measured 20 inches from the exhaust, with the engine running at a designated rpm. For example, a 450cc quadcycle tested at 3,750 rpm.
AMA Pro ATV racing will use the same test on competitors, but instead of measuring machines at a designated rpm, the test rpm will be determined by the formula of 306,000 divided by the engine’s stroke. What this means is that the pro machines will be tested at a slightly higher rpm than in previous seasons.
Amateur racers will still be tested under the old procedures.
Another important distinction for this year’s pro competitors is that the race manager can require post-race sound testing. In that event, the AMA technical inspector will conduct the test, and the machine must meet a sound limit of 101 decibels.
Given the stricter requirements and the proximity of the first round of the series - the ATV Southern Nationals at Mill Creek Motocross Park in Pell Alabama , March 10-11 – Pro riders will be permitted a grace range within 3 decibels of the maximum limit of 99 decibels for the first four rounds of the series.
Thereafter, Pro riders must meet the 99-decibel limit by the fifth round - the Birch Creek National at Birch Creek in Danville, VA , April 28-29.
The 12-round Series revs up on March 10-11 with the ATV Southern Nationals at Mill Creek MX Park, located in Pellcity alabama, and concludes August 11-12 with the Loretta Lynn’s Dirt Days, in Hurracane Mills- end -