Sound system equipment : headphones and earphones associated with portable audio equipment - maximum sound pressure level measurement methodology and limit considerations - part 2 : matching of sets with headphones if either or both are offered separately 音响系统设备:便携式音频设备用头戴式受话器和耳机.最大声压级测量方法和限值考虑.第2部分:单独使用一个或同时使用两个时头戴式受话器设置的匹配