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