Most states and most manufactures use the SAE standards and testing procedures for determing these levels, But local authority rules in some cases Ie were when and how you can determine this is a real can of worms. Most pwc and boats with stock mufflers are at or below the recomened level You also can go on line and find your state testing procedure for most any given PWC or BOAT There are a ot of rules to make the test fair and impartial. GOOD LUCK
LAGING HANDA