The police have bought 12 Acoustic Hailing Devices (AHD) at a cost Tk 50 lakh each for the purpose of driving away protesters. Although it is a non-lethal weapon, the AHDs give out a piercing sound, which, health experts say, can seriously damage hearing of people within a 1km radius. AHDs allow law enforcers the option of scattering crowds without going anywhere near them. The high pitch sonic beams are supposed to be administered following specific guidelines, i.e. operators of these devices are not supposed to emit a sound that crosses the 130 decibel threshold. Health practitioners claim that sound emitted at a level over 85 decibels can cause hearing loss.