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Why do Semi Trucks Make Loud Noises (Explained & Solved)

Noise is inevitable in a working semi truck. While some are harmless noises, others aren’t so innocuous.

Thus, you need to identify which noise requires a mechanic, which is less urgent, or which is violating the law.

If you’re curious as to why your semi truck produces loud noises, let’s find out all the reasons in this article.

Here’s the rundown of why Semi Trucks make Loud Noises

Semi trucks are heavy-duty machines that have naturally loud engines when in operation. Loud noises can be attributed to a faulty engine at times. Semi trucks also make extremely loud noises when features like brake retarders or horns are used, with noise levels ranging from 100 to 175 decibels.

Why do Semi Trucks Make Loud Noises?

Semi trucks use various types and sizes of engines. These factors affect the level of noise of a vehicle. 

For instance, if your semi truck is using a diesel engine, expect to hear a louder noise. If you want your semi truck to generate quieter sounds, install a gas or petrol engine.

Don’t fret if your semi truck produces loud noises. It’s normal for a semi truck especially commercial ones to give out louder sounds than a regular car.

As long as the sound is not intentional and you’re not insinuating alarms or breaking regulations, you’re good to go.

However, if the loud sounds seems new to your ears, don’t hesitate to have your semi truck checked.

Aging is the most common reason for loud noises from your truck. Due to wear and tear, tons of vehicular problems will occur and these will generate loud noises. 

Do you hear a tapping noise from the exhaust? If yes, then your car is probably experiencing an exhaust leak.

How about a shoe tapping sound? Well, your truck got problems with its engine.

While it’s easy to get used to the sound of your semi truck, don’t take it for granted. Otherwise, you’ll face a hefty repair cost.

How Much Noise does a Truck make?

The noise level of vehicles are measured in decibels (dB). A semi truck produces between 80-100 dB.

Knowing and controlling the decibels a semi truck makes is important because states have noise laws for cars and trucks.

Take note that the legal limit of semi trucks in most states is 95 dB. Check your state law as this limitation may vary.

Why are Diesel Engines in a Semi truck so Loud?

Diesel engines have many more advantages than other type of engines. Hence, they are loved by motor enthusiasts.

They don’t require regular maintenance and provides more torque and power. However, their one major drawback is its noise.

Diesel engines are louder than other engines because they perform under higher pressure. For instance, the fuel of a diesel engine is already injected inside the compression of the cylinder.

The overcrowded small components such as metal caps, oil pipes, and small valves also add to the noise.

However, there are a lot of ways to reduce the sound of a diesel engine and without compromising the power of your semi truck.

Some remedies that you can make to reduce at least 10 to 15 dB from the diesel engine are the following:

Sound damping material. This is the most cost-effective way to lessen the level of noise of the engine. Put the material in comprehensive areas to absorb sound. These areas could be the firewall, cabin, and engine bay.

Synthetic engine oil. If you have the budget, use synthetic oil for lubrication. They provide a better result than regular oils. The PTFE (Teflon) ingredient is great in coating your engine’s moving parts. This reduces noise and friction.

Additives. If you want a cheaper oil, go for oil-based additives. It will also create a protective coating on the engine. This will also reduce friction and sound.

How Loud are Semi Truck Diesel Engines?

Approximately, a semi truck diesel engine produces 100 dB of noise. This is loud enough to distress people nearby. 

On top of that, most semi trucks are used for construction and their equipment may also produce a loud sound.

This situation will not only put people’s ears in jeopardy but cause their safety at risk.

To imagine how loud is 100 dB, remember that a normal conversation is 60 dB and a running motorbike is 95 dB. If you hear 70 dB of noise for a prolonged period, it may cause damage to your hearing. 

Hence, hearing a 100 dB from a diesel engine may cause immediate harm to your ears.

Why do Semi Truck Horns make such Loud Noises?

Horns work with compressed air that causes the diaphragm of a horn to produce a loud sound. They are loud for a reason.

 As you know, horns are not used to honk at people so they could walk faster while crossing the streets. 

Its purpose is to alert people to prevent hazards and accidents. Hence, the need to be loud. Imagine the number of accidents there would be without these horns.

The loudness of the horn has to prevail over the sound of other surrounding vehicles and the truck engine itself for it to be heard and be effective.

How Loud is a Semi Truck Horn?

The levels of noise that semi truck horns make are louder than a regular vehicle. The reason is obvious. Semi trucks are heavy objects and it is frightening to imagine it going of course.

A semi truck horn can produce 100-150 dB. It is loud enough to be heard in case of emergencies. 

Since many people make fun of horns and cause panic to other people, states imposed laws to regulate their use.

Of course, different places would have varying laws and regulations. But for most states, truck horns are limited between 150-175 dB.

Why do Jake Brakes in a Semi Truck make Loud Noises?

Do you hear the loud sound the semi truck makes when it suddenly stops? Well, the driver might have used the jake brake rather than the usual foot brake. 

Oftentimes, a jake brake is used to control the speed of a semi truck as it passes a steep road.

When it is used, it activates the exhaust valve located inside the engine’s cylinder creating a loud noise.

How many Decibels is a Jake Brake?

A properly muffled jake brake can generate 85 dB. This is the lowest sound it could make. However, when it is poorly muffled, its starting noise level could be as high as 105 dB. 

The sound of jake brake is comparable to a gunshot. Thus, it can create disturbances in the vicinity. For this reason, they are heavily regulated. 

In some states, the jake brake is prohibited in public places and residential areas to prevent panic and annoyance to people.

Why do Brake Retarders in a Semi Truck make Loud Noises?

Brake retarders are often called collective jake brakes. So, it typically works like a jake brake. It slows down vehicles in difficult situations without causing harm to the brake system.

However, while brakes retarders are powerful, their downside is their noise level. When it is activated, the energy stored inside the compression will produce a loud noise.

This vehicle component is mostly used by commercial trucks like semi-tractors, delivery, and heavy trucks. It plays a vital role in the cost-effectiveness of commercial vehicles. 

How Loud are Brake Retarders on a Semi Truck?

Retarders can produce 80 – 110 dB of sound level. For this reason, local government units and concerned citizens have issues with their noise.

Have you ever heard the clutter of a machine gun? That’s how a brake retarder sounds like.

Since a retarder is important in heavy trucks, you can’t prohibit manufactures to stop installing them on these vehicles.

After all, retarders provide safety and confidence to the drivers while driving a semi truck.

But when noise problems become prevalent in an area, most local governments put up signs on the highway prohibiting truck drivers to use brake retarders.

How do Noise Regulations Affect Trucking Operations?

Noise regulations heavily affect trucking operations. This is because the most important parts of a working semi truck like the engine and brakes normally produce loud sounds when used. 

As such, when loud noises are prohibited in a certain area, the safety and the effectiveness of the semi-truck are compromised.

Not to mention that it also affects the confidence of the driver on the road.

However, we should respect when these kinds of laws are imposed. As a rule, “the welfare of the people is the supreme law.”