DENVER (KDVR) — If you’ve ever encountered someone driving a vehicle so loud that you just know it shouldn’t be legal, you might be onto something.

At least in Colorado.

That’s because there’s a law designed to reduce noise on roads by requiring mufflers.

Mufflers are devices that dampen sound from internal combustion engines.

What does the law say?

Colorado law doesn’t allow any modifications that cause “excessive or unusual noise,” and you aren’t allowed to install a bypass or cutoff for the muffler.

The law doesn’t list what decibels — or sound levels — are acceptable or unacceptable. However, any aftermarket mufflers can’t be any louder than what originally came with the vehicle.

Because electric vehicles don’t have mufflers, the law doesn’t apply to them.

But if you’re caught with an aftermarket muffler that’s too loud — or if you’ve decided to bypass your muffler to make your car louder — you can face a fine of up to $100.

People in commercial vehicles that don’t have mufflers face a fine of up to $500.

What about other states?

The laws on mufflers vary from state to state, with some having stricter laws and others less so.

People are only required to have mufflers and not use bypass or cutoff devices in Texas, Wyoming, Utah, Kansas and New Mexico. The law in Nebraska is similar to the one in Colorado.

A few states, including California, Oregon and Washington, have specific decibel levels that are acceptable.

For example, in California, sound levels on vehicles smaller than a light truck or van not being allowed to exceed 95 decibels, which is around the same level as an average motorcycle, according to the Centers for Disease Control and Prevention.