Whether you ride a motorcycle or you’re simply curious about their functionality, you may be wondering why motorcycles are louder than other types of vehicles. It is a curious thing because motorcycles are smaller so it sometimes doesn’t make sense that they make more noise.
Why are motorcycles so loud? Motorcycles are loud because of the size of the muffler, the length of the exhaust pipes, and the lack of residence time the air and exhaust have to slow down. Additionally, the engine is open to air and atmosphere with no engine compartment encasing and stifling the sound.
Having modified many motorcycle exhaust systems in my day, I’ve become quite familiar with how this affects a motorcycle’s volume. In this article, we’ll explore the reasons behind why motorcycles are so loud and discuss the engineering, cultural, and regulatory factors that contribute to their unmistakable noise.
Why Motorcycles Are So Loud
I often get the question from riders and non-riders alike about why they’re so loud and if motorcyclists do that on purpose. Though the answer may be simple, it does a deserve a detailed explanation. Being a mechanical engineer by profession, I’ll get a little nerdy here.
When you think of a car and how silent they can be, it’s no wonder people think about why motorcycles are louder. But you do have to remember that cars have a bigger muffler compared to motorcycles. It’s actually about 3-4 times bigger than a motorcycle’s muffler. A muffler is what deadens the sound that is coming out of the engine through the exhaust.
Motorcycle mufflers are much smaller, usually no longer than several inches long. That is the biggest reason why motorcycles can be a lot louder than other vehicles. Motorcycles just don’t have the room for a bigger muffler.
The second reason why motorcycles can be so loud is due to the length of the exhaust pipes. The distance from the exhaust port of the engine to the end of the exhaust on most vehicles is 10 – 15 feet long, whereas on a motorcycle it is only about 3 feet.
The sound and the air rushing out of the engine doesn’t have as much residence time inside the pipe to slow down, bounce off the internal walls, and lose some of it’s energy and velocity. In other words, because the exhaust pipes are shorter on a motorcycle, there is a higher force of exhaust and air coming out of them which makes a louder sound.
If you’d like to learn more about how a motorcycle exhaust works, you can read my other article “How Does a Motorcycle Exhaust Work? What People Don’t Understand.”
The third main reason a motorcycle can be so loud is because the engine is open to air and atmosphere and there is nothing shielding the sound of the pistons going up and down inside the engine. Most people don’t realize that the these processes that go on inside any type of engine can be extremely loud. You have to remember there are thousands of mini internal explosions per minute happening.
Other vehicles have an engine that is encased in an engine compartment, so a lot of that sound is deadened. A motorcycle obviously doesn’t have that encasing so it’s completely open for any close by ears to easily hear.
Why Are Newer Motorcycles More Quiet Than Older Motorcycles?
You may have noticed that older motorcycles tend to be much louder than newer motorcycles. A lot of people assume that is because older motorcycles were made during a time where it was a fad to have a loud motorcycle whereas nowadays that’s not really so.
There’s actually a lot more to it than that. With older motorcycles, their mufflers have broken down over time and become less effective. Just like any other part or component on a vehicle, the continual usage and air passing through the muffler will eventually break it down. People just tend to not fix the muffler because the break down is gradual and they may not notice it for a while.
Muffler technology, especially in the past few years, has improved tremendously. Newer motorcycles are made with mufflers with the new technology which makes them much more quiet for a longer period of time.
The technology of motorcycle engines has also improved a lot over the years. As time goes on, engines are made more efficiently with evolved resonators inside the mufflers that are much better at cancelling out the noise.
Additionally, some riders get “short pipes” where they essentially delete the muffler altogether. This makes their exhaust pipes shorter. These are incredibly loud and are generally done on older motorcycles. This gives the appearance that older motorcycles are louder.
Why Do Riders Like Loud Motorcycles?
If you’re not the type who likes loud motorcycles, it’s easy to wonder how a rider could like riding a motorcycle that is so loud and not be impacted by it. It can often be annoying for those around them that don’t appreciate it.
There are two main reasons why motorcyclists like having a loud motorcycle. The first reason is that they simply enjoy the loud sound. I can’t give a scientific explanation for that, but some people really do just like hearing how loud their motorcycle can be. It’s a cultural thing.
I personally don’t love having extremely loud motorcycles, but I don’t mind the rumble an older motorcycle has. Perhaps the reasons people love their motorcycle being so loud is so they have a way to show off their ride. The noise will certainly get people to look.
But perhaps the biggest reason motorcycle riders like to have loud motorcycles is for safety. I don’t know about you, but I can frequently hear motorcycles coming from about a mile away. As a driver, this gives me more awareness that there’s a rider on the road to look out for.
Unaware car drivers are the biggest cause for motorcycle accidents. According to HG.org, “The failure of motorists to detect and recognize motorcycles in traffic is the predominating cause of motorcycle accidents. The driver of the other vehicle involved in collision with the motorcycle did not see the motorcycle before the collision, or did not see the motorcycle until too late to avoid the collision.”
Motorcycles And Noise Ordinances
While there may be legitimate reasons to have a loud motorcycle, there can be a few drawbacks. Having too loud of a bike can actually get you in trouble with the law.
Most states in the U.S. have laws about noise ordinances. Moreover, there is actually a federal law that applies to any motorcycle made after 1983. This is known as the Noise Control Act and it regulates how manufacturers make their motorcycles to ensure they don’t make them too loud.
If someone were to make any alterations to their motorcycle to make them louder, they would need to check in with their local laws to see how loud they can legally make it. Cities will have laws stating what decibel is considered too high on the roads. It’s totally fine to make the alterations you want on your motorcycle, a rider just needs to be aware to not make it too loud.
Conclusion
Motorcycles are well known for making a lot of noise. This is because of the smaller muffler and exhaust pipes which results in less residence time for the exhaust to slow down. Motorcycle engines are also not encased in anything, so it’s easier to hear almost everything that is going on inside of them.
Aside from that, motorcyclists seem to enjoy their loudness. The world has accepted that these are just simply louder machines. I personally enjoy the low rumble while out on a ride and associated it with enjoying the open roads. What do you think? Do you you enjoy the noise motorcycles emanate or do you think it’s annoying?
Related Question
What are the noise limits for motorcycles? Each city and/or state is a little different with their laws and a lot of it depends on the speed of the motorcycle, but in general motorcycles (or any other type of vehicle for the matter) should not be any louder than 80-85 decibels.my article here.