GB/T 16405-2025 Acoustics—Measurement of insertion loss of ducted silencers without flow—Laboratory survey method

Scope

This document describes a laboratory alternative pipe measurement method for determining the insertion loss of circular and rectangular resistive silencers and other piping components used in ventilation and air conditioning systems when there is no airflow.
Note: ISO 7235 describes a laboratory measurement method for insertion loss of ducted silencers with airflow.
This document is applicable to silencers designed for flow velocities not exceeding 15 m/s. This method does not consider the impact of airflow-induced noise and is only suitable for silencers where airflow-induced noise does not significantly affect their performance. Since most silencers used in offices and homes are designed for flow velocities below 15 m/s, this document provides a more economical method compared to ISO 7235.
Due to differences in sound sources and the presence of airflow in pipelines, the insertion loss values obtained by this measurement method may differ from those measured in the field. Different sound and airflow fields in pipelines can lead to different results. In this document, the sound field is mainly in the plane wave mode. Since the test is conducted in conventional pipelines, the measurement results are subject to an identifiable upper limit on insertion loss due to the influence of lateral sound transmission caused by vibration of the pipeline wall structure.
This document is applicable to circular silencers with diameters of 80 mm to 2,000 mm, or rectangular silencers with a cross-sectional area within the same range.

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