Here are independent DB Ratings sent via email:

DB Ratings at 100 Ft.
Leslie    S5T-F 116db
Nathan   K5   115db
Nathan   K3  114db
Nathan  M5 114db
Nathan  P5 106db
Nathan  P3 103db
   1275 103db
Omega 3000  103db
Buell Blasters 103db
Truck Horns 101db