Rumbler sirens have a low frequency or tone that sends vibrations up to 70 yards away to alert drivers that an ambulance is coming.

"It is kind of an odd sound that people aren't used to that gets their attention and makes them look around," said Cooper Arvisais, an EMT for Flight for Life. "[Then] they usually see the lights [and pull over]."

Hospital officials said with the increased usage of cell phones and iPods, it has become increasingly difficult to alert motorists that an ambulance is near.

Arvisais said cars and trucks are more soundproof, so drivers cannot hear a siren until it is almost upon them.

"You can have the lights [and] sirens and everything and you are two feet away from [a car's] bumper and [the driver] still doesn't realize you are there," said Arvisais.

Rumbler sirens are becoming more prevalent throughout the U.S. and have been proven to be more efficient in getting the attention of vehicles and pedestrians as well, according to a news release.

St. Anthony's Hospital has outfitted its two primary ambulances with Rumbler sirens. The hospital said they are among the first emergency vehicles in the metro area to do so.

7NEWS uncovered that Denver Health is testing similar technology on one of its command vehicles.

"[Denver Health is] planning on putting them into our next generation of ambulances as we buy them," said Scott Bookman, chief paramedic of Denver Health.

Bookman tested the system on Friday and said he was impressed.

"So far it has been really effective," said Bookman. "I was out [Friday]] testing and at every intersection that we came to, cars stopped sooner, and there seemed to be more awareness that my vehicle was coming through the intersection."

Bookman said the Howler, the system he was testing, sounded "like a subwoofer coming out of a large stereo system." He said, "you can truly feel the ground shaking underneath you."

Arvisais said the Rumbler vibrates cars directly infront of where the ambulance is driving. He said people walking on the sidewalk or who live in the homes along the street where the ambulance is driving will not feel the vibration.