When gunshots rattle some Denver neighborhoods on Friday night residents should not be alarmed.

The Denver Police Department will be testing its ShotSpotter system from 8 p.m. to midnight, according to a flier that has been posted on the department’s District 2 and District 4 Facebook pages.

District 2 covers Northeast Denver and District 4 covers the west and southwest portions of the city. The District 2 notification specifically addressed the Park Hill neighborhood.

When police first tested the ShotSpotter system in January 2015, the department ended up apologizing to neighbors in multiple northeast neighborhoods because it failed to give widespread notification. The shots were heard beyond the immediate neighborhoods where police were firing their guns.

ShotSpotter is a network of acoustic sensors that can detect gunfire and pinpoint the shooter’s location. The system is designed to speed police response time to shootings and increase weapons-related arrests. It can differentiate between the sound of gunshots and other loud city noises.

The Denver Police Department was the first law enforcement agency to use the technology.

Denver police keep exact locations for the system a secret. It is not deployed city-wide.

In December, the department asked for $525,000 to expand ShotSpotter, saying it had been successful in leading detectives to shooters and in helping them confiscate guns from criminals.

On Friday night, officers will be firing into a bullet trap. There should be no danger to the public, the police flier said.

Neighbors should expect to hear multiple shots during the four-hour testing window.

Noelle Phillips: 303-954-1661, nphillips@denverpost.com or @Noelle_Phillips