Exhaust drone is an annoying, monotone sound and vibration that occurs in some aftermarket exhaust systems. It’s usually caused when the frequencies of the engine and exhaust are aligned at a certain RPM (typically 2,000-3,500 RPM). Drone is most noticeable at highway speeds, not during acceleration or low-speed driving.
You’ll never hear exhaust drone in a car that uses the stock exhaust system. That's because engineers reduce unwanted exhaust noise through design before the car ever leaves the factory. It's only when you start modifying your exhaust system that you can experience exhaust drone.
What Causes Exhaust Drone?
Exhaust drone is caused by the sound frequencies of the engine and exhaust resonating with each other. When the resonance frequencies are the same, they’re likely to create a pressure wave. This is why drone occurs at a specific RPM (which is different for every car and exhaust). Drone is more common with a loud, low-frequency exhaust. This creates a hollow buzzing that can grate on your ears.
Drone is also more likely to occur with track exhaust systems. These loud, performance-oriented systems are designed to give you a high-volume exhaust note. That often comes at the expense of comfort for your ears. You might even feel it resonating in your rib cage or teeth. Mufflers or resonators in track exhaust systems won’t be as effective at preventing drone compared to stock.
The resonator and muffler reduce exhaust drone.
Not every aftermarket exhaust system is going to have drone. In fact, most don’t, and many are specifically designed to combat the phenomenon. Some people are happy to trade sound and performance for some drone on the highway. Others are more comfortable with an aftermarket system that’s engineered to have no drone at all.
Will a Muffler Delete Cause Drone?
Getting rid of (deleting) your muffler has a good chance of causing drone. It’s true that the primary job of the muffler is to lower your volume, not change the pitch or tone. However, there are also acoustic properties within the muffler itself. The baffles can change the frequency and affect drone.
Your muffler will reduce overall exhaust volume, which can reduce drone.
Plus, removing your muffler will make your system louder overall. If there were bothersome frequencies before, they may have been quieted and unnoticeable. More volume means a higher chance you’ll hear any drone that may exist. Putting your muffler back on is a good way to combat drone.
Do Resonators Reduce Exhaust Drone?
One of the primary purposes of a resonator is to reduce exhaust drone. In addition to creating a tone that engineers think will sound good for the car, a resonator mitigates frequencies that would otherwise cause exhaust drone.
A resonator is important for changing your exhaust sound and reducing drone.
This means that one of the best solutions for solving exhaust drone is to change or add a resonator. If you’ve deleted your resonator as part of an exhaust upgrade, consider adding it back. Or select a cat-back exhaust kit with a resonator specifically designed to reduce drone.
Remember that resonators and mufflers work together. You can probably get away with not having one of them. But deleting both will greatly increase your chance of experiencing exhaust drone.
How Can You Reduce Exhaust Drone in Your Car?
The exact cause of exhaust drone isn’t always easy to isolate. Adding a resonator is the best way to get rid of drone. A muffler also has a good probability of success. If you don’t want to go with either of these components or haven’t gotten results, you can try adding sound insulation or modifying other parts of the exhaust system.
Add Noise Insulation
One solution for exhaust drone is adding noise insulation. This won’t address specific frequencies, but it will make things quieter and reduce vibration. Sound deadening can be used to reduce overall decibel level in the cabin. CLD (constrained layer dampener) tiles and other noise insulation, like Dynamat, work well. Even simple things, like keeping your spare tire in its place or using carpeted floor mats, can have an effect.
Add Resonated Exhaust Tips
Resonated exhaust tips are designed to slightly change your exhaust note. Since your tailpipes can be a cause of drone, changing the tips is a way to dampen or adjust the frequency. They don’t make a massive difference, but the modest tweak in acoustics might be enough to get rid of exhaust drone. Plus, they’re affordable and can add style to your exhaust pipes.
Taking steps to reduce exhaust drone will improve your comfort while driving.
Additionally, installing exhaust tips of a different size can change the overall length of your exhaust piping. Changing the length of the pipes is a surefire way to change the frequency. However, it’s not cost-effective to try dozens of different pipe lengths to find the right one.
Change the Entire Exhaust System
Another, more drastic solution is to change out your entire exhaust system. If you don’t want to mess with your resonator and muffler (or already tried), an entirely new system could be in order. No-drone systems have become very popular, and many companies offer different technologies to help cancel out drone.
Unfortunately, there will have to be some trial and error if you’re dedicated to getting rid of drone and still having a loud exhaust system.
Sources: It Still Runs