Text Box: Sound Limits Could Cost the Solo Community $2.0M
Text Box: Introduction Sound limits have become a hot topic on many Solo boards these days. Are the cars too loud? Are sound levels costing us sites? Are the sound levels approaching dangerous levels? Are the current rules adequate? These are the questions which are being debated and the SCCA has taken notice. The SCCA monitored sound levels during the SCCA National Tour at Milwaukee. MLS Motor Racing has obtained a copy of these results, and our own 1998 Camaro SS came in at 105dB. A copy of the raw data can be found in the SCCA Raw Data tab below. Analysis Utilizing this data it is possible to estimate how many vehicles may not be within compliance at different max allowable sound levels based on the following assumptions: 1. The SCCA test is accurate and repeatable. This would be confirmed by performing a Gauge Repeatability and Reproducibility (GR&R) study. 2. The vehicles sampled at the SCCA Milwaukee National Tour are a homogenous representation of the entire Solo Racing community 3. There are approximately 13,000 Solo racers nation wide. This is based on the fact that there were over 91,000 solo entries in 2007 and we'll assume that the "average" competitor entered 7 events. 4. The average cost of modifying a non-compliant exhaust system is $200. For some competitors it may cost less. They may be able to bring the car into compliance by installing a turn down. Others may spend more than $200 because they may have to install a new "cat- back" system. We have made a few substantial assumptions in our calculations for cost. These assumptions need to verfied by the SCCA. The bottom chart on the right show that the sample taken in Milwaukee fits the normal distribution. When we perform the capability analysis, upper graph, we see that the average car sound level is 94db and the standard deviation is 8.17db. If the upper limit is set to 100dB, 22.93% of the vehicles would be out of compliance. Using probability theory we can determine the percentage of vehicles that would be out of compliance at different sound levels, see Table 1. For example, if the limit was set at 100db, 23%, or 2293 cars would not be in compliance. When the limit is reduced to 88 db, (The OSHA max limit for an 8 hour shift without hearing protection), then over 75% of the vehicles would not be in compliance. If there are 13,000 competitors, the cost to the solo community to meet an 88db requirement would approach $2.0M. Conclusions Sound limits may make sense, especially at event sites where high sound levels could affect the availability of the site, but at what cost? This question is probably better answered by individual regions. However, at sites where sound is not an issue, it is hard to justify the expense of compliance, especially if that cost could exceed $2.0M. The perception of "adequate sound levels" varies from racer to racer and to person to person. To some 100db my be OK, but others think 90db is the way to go. Also, the repeatability and reproducibility of the measurement system for determine sound levels needs to be investigated. Sound meters are measurement devices just like weight scales. We all know that weight scales must be accurate and repeatable. Nobody would disqualify a car with a set of scales that did not report the same weight for a known mass repeatedly. The same has to be true with the sound meters prior to implementing a sound limit requirement. Lastly, this analysis was done taking only one sample of the solo population and it is assumed that this sample is a homogenous representation of the solo community. In order to gain more confidence in the data, more sampling should be complete, not only at National Events, but also at the local level. Ideally all measurements should be taken with the same sound equipment, by the same operator to minimize variation due to gauge variability. Personal View Many of our fellow competitors have told us that the MLS Motor Racing Camaro is "extremely loud," but it never seemed that loud to us. Now we have data from the SCCA that reinforces their opinions. Since our car tipped the meter at 105db, we have decided to research options to reduce this sound level without reducing engine performance or adding weight. And of course, we still want it to sound "good."
Table 1
Proposed Limit Percentage of Cars That Will Exceed Proposed Limit Number of Cars That will Exceed Proposed Limit Total Cost
110 2.47% 322 $64,320
108 4.27% 556 $111,100
106 7.01% 911 $182,220
104 10.92% 1420 $284,060
102 16.21% 2107 $421,460
100 22.93% 2981 $596,140
98 30.98% 4027 $805,360
96 40.06% 5207 $1,041,460
94 49.71% 6463 $1,292,500
92 59.38% 7720 $1,543,980
90 68.51% 8907 $1,781,340
88 76.63% 9962 $1,992,420
86 83.43% 10846 $2,169,260
Mean: 93.94
Standard Deviation: 8.17
Number of Solo Competators: 13,000
Average Exahaust Upgrade Cost: $200