As some cities deploy "sound cannons" to communicate with and disperse crowds gathered for recent Black Lives Matter protests, an association representing speech and hearing professionals is warning that the devices can cause permanent hearing damage.

The American Speech-Language-Hearing Association issued a statement Tuesday cautioning against the use of long-range acoustic devices, or LRADs, used by police departments. The devices, which were originally designed for military use, can be used as public speaker systems that drown out noise created by protestors. However, they can also be used as a form of crowd control by emitting loud sounds that cause discomfort and disorientation.

ASHA said it was disturbed by news reports that some cities had used LRADs during recent protests. They noted the devices can emit sounds up to 162 decibels, which can cause migraines, balance loss, permanent hearing loss and other auditory issues.

"Proponents say these devices, which have speech communication capability, are needed for purposes such as making public addresses to large or noisy crowds," ASHA said. "Yet, the decibel level of speech presented through LRADs is unsafe, capable of causing temporary and permanent hearing loss for those in front of, behind, or on the periphery of the device. And the troubling fact remains: LRADs have been and can be easily s.et at extremely high decibel levels that can cause serious lasting harm."

ASHA is not the first association to criticize a form of crowd control used by law enforcement. The American Academy of Ophthalmology recently condemned the use of rubber bullets, noting the ammunition has caused permanent eye damage and blindness.

AAO called for law enforcement to stop using rubber bullets. ASHA didn't go that far in its criticism of LRADs, instead saying it was encouraged by reports that some cities were taking steps to ensure the safe use of the devices. It also advised people heading to large public gatherings to wear sound-reducing earplugs or earmuffs and to hide behind brick or concrete walls if the devices are used.

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