The House is poised to pass legislation legalizing the use of gun silencers as early as this week, a move that critics say could make it more difficult to identify where gunshots are coming from during a mass shooting like the one that took place in Las Vegas Sunday night.

A provision called the Hearing Protection Act, tucked into the bipartisan Sportsmen Heritage and Recreational Enhancement, or SHARE Act, would eliminate restrictions on silencers and instead treat them as ordinary firearms. Under the National Firearms Act of 1934, suppressors – along with "destructive devices" such as grenades or rocket launchers, "sawed-off" shotguns and machine guns – require federal registration and a special license to own, as well as a $200 tax stamp to purchase that would also be repealed under the proposed law.

A hearing on the bill was initially scheduled for June 14 – the day of the congressional baseball practice shooting that injured House Majority Whip Steve Scalise – but was postponed until early September. It passed out of House Committee on Natural Resources on a party-line vote of 22-13 on Sept. 13 and would be expected to see a similar result when put up for a vote in the full House. Democrats in the Senate are expected to block the measure.

Proponents of the Hearing Protection Act say suppressors are unfairly maligned and make it harder for hunters to hear their surroundings, potentially endangering them and others.

But gun control advocates have slammed the measure as a boon to manufacturers of silencers, whose sales has been slumping in recent years. They also point out silencers would make it much more difficult for law enforcement to stop shooters like the one who opened fire on an outdoor music in Las Vegas, killing at least 50 and injuring hundreds of others Sunday night.

"Law enforcement and military experts have told the American people and Congress they oppose this bill, and that there are very effective hearing protection devices already available on the open market," Kris Brown, president of the Brady Campaign to Prevent Gun Violence, said in a statement after the bill passed out of committee. "Keeping guns out of dangerous hands and stopping school shootings, ambushes of police and other mass shootings before they can start is the priority for the American people – not making it harder to detect a shooting once it starts."

Las Vegas Police say Stephen Paddock allegedly opened fire from the 32nd floor of the Mandalay Bay Resort and Casino, above the Las Vegas Strip, where thousands were attending the Route 91 Harvest Music Festival. Country singer Jason Aldean, the headliner, was on state at the time the shooting began, shortly after 10 p.m.

In video of the shooting taken by bystanders, Aldean can be heard continuing to play for about 15 seconds after rapid gunfire can be heard. The musicians stop playing and the stage lights go off as concert goers recognize the sound of the shots and begin to take cover.

At least 400 people have been taken to hospitals, police say.