NS-EN ISO 389-9:2009
声学 听力测定设备校准的参考零 第9部分:确定参考听力阈值水平的首选测试条件 (ISO 389-9:2009)
Acoustics — Reference zero for the calibration of audiometric equipment — Part 9: Preferred test conditions for the determination of reference hearing threshold levels (ISO 389-9:2009)