MuckRock has been filing requests around long range acoustic devices in an effort to learn about policies, usage, the variety of different devices, and the price tags involved with these high powered sound cannons. So far, we have managed to get some particularly illuminating material from Chicago, Houston, and the Massachusetts State Police.

Records released last week show D.C. Metropolitan Police Department employed a Long Range Acoustic Device during the Women’s March to “direct the crowd flow.” This is the latest evidence of an worrying trend in which police departments are increasingly using the incredibly powerful LRAD to deal with non-violent protests at the risk of causing permanent hearing loss.