You want loud??
Kleinn builds a 2 chime and a 3 chime set.
Desert Rat sells the for $100 and $200 respectively.
I am working on a sound/video clip of mine.
The 2 chime was wicked, then you add a 3 chime set (total of 5 now) to it backed with 150 psi and 3/8" air tubing, It will viberate the sheet metal of the truck.

If money is no real object there are several sets out there that will wake up the dead. I believe the 3 chime with the big air tubing is rated at 159 db at 3 meters, only a wimpy 152 with the 1/4" hose. They are simple and light weight with real nice diaphram housings.

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07.5 3500 Quad, SRW, 4X4, Laramie, Leathered, Dark Metallic Gray, 6.7, 68RFE, 20K Reese, Ride Rite's, 2 Viair air compressors, Bully steps, Kleinn Locomotive air horns (5 in all), Billet polished locking fuel door, 'A' pillar mount Auto Meter Pryo, PML X-deep trans pan
06 Durango 285 RL 5'er Lifted by KZ