In the Jinrongjie area of Beijing, a public square has for years served as a venue where amateur dancers gather at night. However, their loud music led to frustrated local residents calling the Beijing 12345 Citizen Hotline to complain about the noise. They included schoolchildren who said they struggled to do their homework. Eventually, a solution was found, in the form of innovative directional sound wave technology. The CGTN documentary "Hotline Beijing" reveals how local officials, scientists and residents worked together to restore harmony to one community.