ISO 11691:2020
Acoustics — Measurement of insertion loss of ducted silencers without flow — Laboratory survey method

Standard No.

ISO 11691:2020

Release Date

2020

Published By

International Organization for Standardization (ISO)

Latest

ISO 11691:2020

Scope

This document specifies a laboratory substitution method to determine the insertion loss without flow of ducted, mainly absorbent, circular and rectangular silencers, as well as other duct elements for use in ventilating and air-conditioning systems. NOTE Laboratory measurement procedures for ducted silencers with superimposed flow are described in This document is applicable to silencers where the design velocity does not exceed 15 m/s. As the method does not include self-generated flow noise, this document is not suitable for tests on silencers where this type of noise is of great importance for the evaluation of the silencer performance. As most silencers, particularly in offices and dwelling, have design velocities below 15 m/s, this document can often be a cost-efficient alternative to ISO 7235[5]. The insertion loss determined according to this document in a laboratory is not necessarily the same as the insertion loss obtained in an installation in the field. Different sound and flow fields in the duct yield different results. In this document, the sound field is dominated by plane wave modes. Due to the use of regular test ducts, the results can include some flanking transmission via structural vibrations in the duct walls that sets an upper limit to the insertion loss that can be determined. This document is intended to be used for circular silencers with diameters of 80 mm to 2000 mm or for rectangular silencers with cross-sectional areas within the same range.

ISO 11691:2020 Referenced Document

• IEC 60942 Electroacoustics - Sound calibrators
• IEC 61183 Electroacoustics - Random-incidence and diffuse-field calibration of sound level meters
• IEC 61260-1 IEC 61260-1: Electroacoustics - Octave-band and fractional-octave-band filters - Part 1: Specifications
• IEC 61672-1 Electroacoustics - Sound level meters - Part 1: Specifications
• IEC 61672-3 Electroacoustics - Sound level meters - Part 3: Periodic tests
• ISO 3741 Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Precision methods for reverberation test rooms

ISO 11691:2020 history

• 2020 ISO 11691:2020 Acoustics — Measurement of insertion loss of ducted silencers without flow — Laboratory survey method
• 1995 ISO 11691:1995 Acoustics - Measurement of insertion loss of ducted silencers without flow - Laboratory survey method