Motorcyclists get a bad rep for the noise pollution they cause while casually riding through the street. They annoy the regular car drivers and wake up babies in their cribs. There are several reasons why motorcycles are so loud, and we’ll address them in this article.
Motorcycles can be loud for many reasons: a stock exhaust system replaced by a loud aftermarket one is the main reason. The second reason is a muffler that’s broken down and hasn’t been replaced, something that is quite common on older motorcycles.
Motorcycles are in general louder than cars because the motorcycle exhaust pipe is shorter so the engine noise escapes into the environment before it’s had a chance to quiet down. It’s also the case that motorcycle engine compartments are not sound deadened as those in larger vehicles, so more of the engine noise can escape through the engine encasing itself.
1. Aftermarket exhaust system
Motorcycles are actually not too loud in their original format. They are typically under 90 dB when straight from the factory. However, many owners replace the stock exhaust system with a louder one. This is sometimes done to increase the power of the motorcycle, but often it’s also done precisely to make the motorcycle louder.
But why make it louder to being with? Well, that’s a question that only the owner can answer! But the most common reasons are:
- to show off: in my estimate the most common reason
- for safety reasons: loud pipes saves lives, a loud motorcycle is better heard by other drivers, lowering the chance of an accident, even though some people disagree because the pipe and sound are pointed backwards and so it does very little to warn the drivers up ahead
- more power: some riders will sacrifice their ear drums for a 5-10 increase in horsepower
- they damaged the stock exhaust system: so they had to replace it with something, and the aftermarket exhaust is louder
2. Harley engines need to be louder
Stock Harleys have very restrictive air cleaners and exhaust systems. The exhaust also has a catalytic converter which restricts air flow even further. This is why its engine is put under a lot of pressure as the air/fuel flow is exceptionally low.
So many Harley owners decide to let their engine breathe, and they do this by removing these obstructions. They replace the air cleaner and exhaust system with a more free-flowing aftermarket version and remove the catalytic converter in the process. Now the engine is much more powerful, but unfortunately it’s also very loud.
Some riders install straight pipes with no internal baffles which are EXTREMELY loud, and completely unnecessary. This is where the outrageous noise produced by some Harleys comes from. Also, a straight pipe adds nothing to the performance except on high rpm, so owners who install them are specifically interested in the obnoxious noise and aren’t doing it for performance.
As I said, don’t judge every loud biker as being obnoxious on purpose, because sometimes it’s justified to increase noise in order to improve performance, and at other times it’s done for the sound increase alone.
3. Older motorcycles were made louder
It’s true that in previous decades it was considered cool to have a louder motorcycle, so they were manufactured with that in mind. Nowadays you’ll notice that newer motorcycles are much quieter, and that’s because the mufflers are made with newer, quiet technology and the engines are better as well.
If you happen to meet an old motorcycle on the road that’s pretty loud, it could also be the case that its muffler has broken down over time and become less effective.
4. The exhaust pipe is short
When comparing motorcycle and car loudness, you have to take into consideration the length between the engine and the exhaust port. In cars that length is usually 10 to 15 feet long while on motorcycles it’s only about 3 feet. This means that the sound coming from the engine doesn’t get lessened as much before it goes into the environment.
5. The engine compartment lacks sound insulation
Some of the noise comes directly from the engine compartment itself. The processes of pistons going up and down inside the engine along with thousands of mini explosions per minute occurring simultaneously.
A motorcycle engine is not encased in thick, sound deadening material that cars usually are because then the engine compartment would be too large and ruin the aesthetics and driving potential of the bike. Unfortunately, the less thick material there is between the source of the noise (engine) and the external environment, the greater the perception of noise will be.
6. Quiet motorcycle helmets
While the regular passerby is extremely irritated by the noise from a motorcycle, the rider can be oblivious to it because he has a quiet helmet.
Many motorcycle helmets nowadays are designed to provide a quiet riding experience. They’re made from a combination of thick encasing on the outside and very dense foam on the inside which soaks up much of the noise before it can reach the rider’s ears.
The rider could also be using a headset and listening to music which would further conceal the noise from his/her ears. But the other drivers and pedestrians don’t have this luxury so the animosity between the two parties continues.
Read More: Quietest Motorcycle Helmets Tested Reviews
Final Word: Why are Motorcycles so Loud
Motorcycles are not necessarily loud. Based on factory settings they are typically under 90 dB, but the upgrades to exhaust system made by many owners can make them much louder than that. The reasons for these upgrades are numerous, from road safety and improved engine performance to pure attention seeking. So I hope this article has cleared up some misconceptions in regards to motorcycle noise.