The Phoenix Police Department wants to purchase two powerful loudspeakers that have been used by some law enforcement agencies to force protesters to disperse.

The model of Long Range Acoustic Devices (LRADs) that Phoenix Police want to buy is capable of producing piercing noises reaching 154 decibels, louder than a jet engine.

Humans begin experiencing discomfort at 110 decibels. Acute hearing loss can occur from exposure to noises above 140 decibels.

Police Chief Jerri Williams said during a Phoenix City Council meeting in June that the department would use the LRAD system to communicate with large crowds.

The need for two LRADs became apparent after the August 22 protests outside a rally for President Donald Trump, she told councilmembers. The department is facing a lawsuit over its response to the protest, which claims that police used excessive force and did not give warnings before using tear gas and pepper ball munitions to disperse the crowd of anti-Trump protesters.

Trump is planning to return to Phoenix in late September. If the purchase is approved, the LRADs would not be ready to use by Trump's visit.

Making a case for the city to purchase the LRAD system, Williams told councilmembers, "This system will allow us to communicate to our community members accurate and timely information so that they can make decisions, and we can direct them to go different places if things get rough downtown."

While the LRADs can be used to deliver messages to large crowds, they can also function as a "sound cannon," "sonic weapon," and "sound gun," to name a few terminologies used by media to describe the machine.

Chief Williams has denied that the LRAD is a weapon, telling city councilmembers in June, "It is not a weapon." She could not be reached for comment.

Mercedes Fortune, a spokesperson for the Phoenix Police Department, would not rule out the possibility of local cops using the LRAD's pain-inducing deterrent tones to disperse protesters.

"I don’t know what will be used or what will not be used," Fortune said. "It will be based on what is necessary. For our purposes, it is for communication purposes only."

She added, "There are different forms of communication."

LRADs have been several police departments to disperse protests using the pain-inducing tones, including during demonstrations in Ferguson, Missouri, and near the Standing Rock Sioux Reservation.

The Second Circuit Court of Appeals ruled in June that LRAD use can constitute excessive force, writing in an opinion, "[P]urposefully using a LRAD in a manner capable of causing serious injury to move non-violent protesters to the sidewalks violates the Fourteenth Amendment under clearly established law."

The case involved seven protesters who claimed the New York Police Department was wrong to deploy the LRAD's piercing tones to disperse them. NYPD attempted to dismiss the suit, arguing that no court had established that LRAD use could be excessive force.

The specific model of LRAD that the Phoenix Police Department wants to buy, the LRAD 500X, would cost $43,134 for two. The department currently has in stock much one much smaller LRAD machine, the LRAD 100x, which Williams told councilmembers was not effective for communicating with protesters during the anti-Trump demonstration.

The LRAD 100x also has the capability to produce the piercing noise, though not as loud as the 500X. Phoenix Police's official after-action report from the August 22 protest suggests officers only used the LRAD to give instructions to the crowd.

Tempe Police Department has one LRAD that it mounts on top of a tactical vehicle, a spokesperson for the department said. Tempe Police gave a demonstration of the device to Phoenix councilmembers on August 22.

The city council's Public Safety and Veterans Committee is scheduled to vote on whether to recommend approval of the LRAD purchase on September 12. After that, the proposal is likely to be brought before the full council.