Manoli Katakis 
Part of the alLure to owning a muscle car or pony car is the raucous noise that spews from the tailpipes. In fact, automakers have scores of engineers that focus on making a car sound delightful.
That fact led the Chevrolet Camaro ZL1 to house one hell of a bark, but for our friends in Australia, Holden Special Vehicles needed to neuter the soundtrack somewhat.
A report from Australian magazine Wheels explains why the Camaro ZL1 is a whole lot quieter than the same car Americans can purchase from their local Chevrolet dealer. Thanks to Australian Design Rule regulations, the Camaro ZL1 needed to meet specific regulations for “drive-by noise.” As in, the noise the car makes as it passes by. These regulations cap noise limits at 74 decibels for cars with automatic transmissions and 75 decibels for models with a manual transmission.
We don’t know what the Camaro ZL1 registered to pass regulations, but we imagine HSV did everything it could to keep the car as loud as possible and still be able to import the pony car, convert it to right-hand drive, and sell it to adoring fans.
This required some modifications, though. Camaro ZL1s sold with the automatic feature two extra resonators at the rear of the exhaust system. Meanwhile, those featuring the manual transmission have a total of four more resonators—two at the rear and two in the front.
The resonators are, specifically, what gives the Camaro ZL1 its hushed tone in Australia. That’s not to say it’s weak, but per the report, the high-performance Camaro does not have the same snarl Americans can enjoy day in and day out.
With the resonators attached, ADR regulations mandated the car must make two passes for sound measurements on each side of the car. The test driver launches the car at full throttle for about 25 feet to take the measurement. Thankfully, the Camaro ZL1 passed.
It’s a rather rigorous process that could have kept the Camaro ZL1 out of Australia if it weren’t for the dedicated gear heads at HSV.
