What is it? Concerns after gov't unleashed an acoustic weapon on Kenyans during anniversary protests

An Armoured Personnel Carrier (APC) rode the streets of Nairobi to intimidate those who had taken to the streets to honour their fallen heroes, raising eyebrows about what purpose it served in a peaceful procession.

The automobile was equipped with an LRAD, or a Long Range Acoustic Device, which is marketed to law enforcement agencies as a "safe solution" for crowd control, but they are not as safe.

These acoustic weapons, also known as sound cannons, project very loud, focused sound over long distances and, in this case, for the purpose of dispersing crowds and protesters.

It blasts this lethal sound up to 160 dB, a sound similar to a 12-gauge shotgun firing close to your ear and extremely lethal.

A safe decibel level for the human ear is 70 dB or below, which medical experts have said is safe for unlimited daily exposure. These sound levels come from a vacuum cleaner, which also becomes an earsore after long exposure.

An 85 dB, such as lawnmowers and heavy traffic, is the recommended safety limit and causes damage after about 8 hours.

Permanent hearing damage is caused after a 15-minute exposure to 100 dB, which is similar to the maximum volume of your mobile phone.

Immediate damage can occur at the pain threshold, which is 120dB and above. These levels are experienced from sirens and even in close-range concerts.

Unlike conventional loudspeakers that disperse audio in all directions, LRADs restrict the sound wave into a highly concentrated path using a narrow beam

This audio beam can be projected anywhere from 600 meters to 5,500 meters away, depending entirely on the size and power of the specific model.

Serious questions remain about the safety and efficacy of these weapons because acute exposure to focused sound can provoke pain, disruption of the inner ear's vestibular system, resulting in dizziness or vertigo and hearing loss.

Safety

Earplugs cannot protect persons from these acoustic weapons since they are not designed to block intense decibel levels, but using layered hearing protection with disposable foam earplugs and industrial-grade over-ear earmuffs can be viable, but will not block the sound entirely.

Acoustic shielding can also work since sound waves deflect off dense materials. One can improvise a barrier using dense objects like brick and concrete walls or a dense physical shield to absorb and deflect the sound waves.

Manoeuvres have also been encouraged since retreating directly backwards along the beam path will still expose the crowds. Combat experts advise sideway movements at 90-degree angles to rapidly exit the concentrated zone of sound.

Use of LRADs on peaceful protesters is strictly illegal for civilian use in most jurisdictions.

Some of them are Serbia, Poland and the United States, which have strict legal regulations prohibiting the active deployment of LRADs for crowd dispersion following agitation from civil rights. 

Although their police forces possess the technology, they are restricted to keeping it inactive during demonstrations.

In Kenya, while there is no specific ban against their use by the National Police Service (NPS), the courts have barred authorities from using excessive police force on peaceful protesters.

Under the Sixth Schedule of the NPS Act, officers are required to first attempt non-violent means, and the use of lethal force is only permissible when strictly necessary to protect life or to prevent a person from committing a serious felony involving violence.