气流管道 meaning in English

airflow line

Acoustics - measurement of insertion loss of ducted silencers without flow - laboratory survey method
声学.无气流管道消声器插入的损耗测量.实验室调查法
Acoustics - determination of insertion loss of ducted silencers without flow - laboratory survey method iso 11691 : 1995 ; german version en iso 11691 : 1995
声学.无气流管道消声器插入损失测量.实验室测量法