Someone cranked up the volume of the public address system.有人调大了公共广播系统的音量。The news was announced on the public address system at the high school.消息是在这所中学的广播里宣布的。A public address system magnifies all the little noises and coughs.有线广播系统把一点点声音、一点点咳嗽都放大了。