ISO 7235:2003规定了测定方法 有气流和无气流的管道消音器的频带插入损失、管道消音器产生的流动噪声（或再生声）的频带声功率级、有气流的消音器的总压力损失以及空气终端装置的频带传输损失。 测量程序旨在用于环境温度下的实验室测量。ISO 11820规定了消音器的原位测量。 应注意的是，根据ISO 7235:2003在实验室中确定的结果不一定与现场（安装）获得的结果相同，因为不同的声场和流场将产生不同的结果。例如，在实验室条件下的压力损失将低于原位，但在不同实验室之间是可比较的。ISO 7235:2003适用于所有类型的消音器，包括用于通风和空调系统、烟气进气和排气以及类似应用的消音器。其他无源空气处理设备，如弯头、空气终端单元或T型连接器，也可以使用本国际标准进行测试。 不适用于机动车辆使用的反应式消音器。

ISO 7235:2003 specifies methods for determining

• the insertion loss, in frequency bands, of ducted silencers with and without airflow,
• the sound power level, in frequency bands, of the flow noise (or regenerated sound) generated by ducted silencers,
• the total pressure loss of silencers with airflow, and
• the transmission loss, in frequency bands, of air-terminal units.

The measurement procedures are intended for laboratory measurements at ambient temperature. Measurements on silencers in situ are specified in ISO 11820. It is to be noted that the results determined in a laboratory according to ISO 7235:2003 will not necessarily be the same as those obtained in situ (installation), as different sound and flow fields will yield different results. For example, the pressure loss will be lower under laboratory conditions than in situ, but will be comparable between different laboratories. ISO 7235:2003 is applicable to all types of silencer including silencers for ventilating and air-conditioning systems, air intake and exhaust of flue gases, and similar applications. Other passive air-handling devices, such as bends, air-terminal units or T-connectors, can also be tested using this International Standard. It is not applicable to reactive silencers used for motor vehicles.