Sound DB levels (race track BAN)

[Excaliber]

Under the RULES section from the NorCal Shelby Club site:
4.1.11 MUFFLERS
Mufflers are required on all cars. The exhaust system must be able to meet the sound limit for the venue: Laguna Seca - 90dB(A), Infineon Raceway - 103dB(A), Thunderhill - 105dB(A). No open exhausts will be allowed.
Note: For Thunderhill exceptions to this rule may be made on a case by case basis, at the discretion of the chief steward or event organizer. There are no exceptions at Laguna Seca or Infineon Raceway.

Apparently the DB reading is taken "at speed" while your on the track.

Exhaust Systems That Don't Work (from the Web Site).

• Open exhaust, obviously doesn't work!
• Glasspack mufflers do not work!
• 3 inch pipe Flowmasters don't work!
• Flowmasters with center inlet or center outlet don't work!
• 3 inch pipe or larger Brand-X mufflers don't work!
• Shorter than 28 inch LoBaks don't work!
• Race style LoBaks don't work!
• Borla mufflers without catalytic converters or without a secondary muffler such as a Supertrapp don't work.
• Monza style exhaust or European high performance mufflers on Ferrari's, Porsche's, etc., don't work.
• Stinger type of exhaust on Porsche's & Mazdas, commonly known as expansion chambers, don't work.

107-110 DB is pretty common for a "Cobra" at highway speed. From what I have found so far you can only expect a FEW DB drop with things like "Supertrapp" exhaust tips, cone inserts, etc. The NorCal club is looking for any ideas that might help, they DO NOT have a 100% solution at this time for Cobras. GT-350's and various street cars are in the same boat with the noise issue.