As posted in the March 2024 Fastrack, the following Technical Bulletin modifies Appendix H in the 2024 Solo Rules:

#35471 Sound Committee: Tech Bulletin

Per the sound committee, modify sentences within the first six paragraphs of Appendix H as follows:

  • First paragraph: “The maximum allowed vehicle sound level will be 100.0 dBA 108.0 dBC.”
  • Second paragraph, second sentence: “The measuring point will be 50 feet from the edge of the course using an ANSI Type 2 sound meter set to “A” “C” weighting, “Slow” response.”
  • Third paragraph: “If a driver in a vehicle exceeds 96 dBA 100.0 dBC, the Chief Steward or his/her designated representative will be notified by the Sound Control Steward or representative. The driver of any run producing a sound measurement over 96 dBA 100.0 dBC  will be notified, as soon as reasonably possible following the run, by the Chief Steward, Sound Control Steward, or representative.”
  • Fourth paragraph, first sentence: “If a driver in a vehicle exceeds 100.0 dBA 108.0 dBC, the driver will be allowed to attempt a viable remedy to functionally alter the exhaust system to reduce the sound level of the vehicle before his/her next run that day.”
  • Sixth paragraph, last sentence: “If the driver in the vehicle exceeds 100 dBA 108.0 dBC again on any subsequent run, that run will be scored a DNF and all additional runs the for that driver will be forfeited.”

For the 2024 season, the maximum limit will be raised to 108.0 dBC to allow drivers to learn and make necessary adjustments to meet the sound committee’s proposed limit of 105.0 dBC for 2025.

The sound committee is implementing the changes shown to Appendix H. These changes are the result of a year-long assessment of the implementation and enforcement of the current rules. The inconsistencies of meter placement, readings, and penalty enforcement per the current rules have made it challenging for competitors to understand and meet the expectations as written. The updates to Appendix H aim to create higher consistency and clear expectations for both event personnel and competitors while maintaining sound requirements for site retention and acquisition, worker safety, and the enjoyment of events.

2024 will be a transitional year for the sound rules. The change from dBA measurement to dBC is expected to increase the reported sound level due to the differences in measurement weighting and as a result we are increasing the sound limit to account for this difference. The higher limit does not reflect an allowance to increase the sound level of a car. The limit for 2024 will be 108 dBC. This raised limit for 2024 will provide competitors an opportunity to learn how loud their cars are when measured to the new standard and at a consistent distance of 50 feet. The expected limit for 2025 will be 105 dBC.

The sound advisory committee is also making the following suggestions to better prepare competitors for national sound rule enforcement:

  • A sound meter should be made available during TnT runs at National Tour events.
  • Regions should have a meter or readings available at events to inform competitors prior to attending National events. In the absence of an available meter, several free phone applications exist.