ISO 11821:1997

Overview

ISO 11821:1997 – Acoustics - Measurement of the in situ sound attenuation of a removable screen is an international standard developed by the ISO Technical Committee on Acoustics. This standard specifies engineering methods for evaluating the sound attenuation performance of removable screens installed indoors and outdoors. Removable screens are often used in industrial and commercial settings to reduce noise exposure at specific locations, such as workstations or work areas near machinery.

The standard defines a practical, repeatable methodology for measuring the insertion loss provided by these screens under actual usage conditions (“in situ”), rather than under idealized laboratory conditions. This is critical for assessing the real-world effectiveness of noise control solutions and informing investments in occupational safety and comfort.

Key Topics

• In situ Sound Attenuation Measurement: Focuses on determining the actual noise-reduction effect provided by a removable screen at the location where it is used.
• Removable Screen Definition: Covers any object (e.g., panel, curtain, mobile barrier) designed to block or reduce sound transmission by breaking the line of sight between the noise source and the area to be protected.
• Applicable Measurement Methods: Both actual noise sources and artificial sound sources can be used, with procedures specified for each.
• Influencing Factors:
  • Diffraction around screen edges
  • Transmission through screen materials
  • Absorption by the screen and its environment
  • Room geometry and reflective surfaces (for indoor applications)
• Measurement Procedure:
  • Requirements for acoustic instrumentation (in line with IEC standards)
  • Microphone placement rules for assessing protected positions and areas
  • Correction methods for background noise
  • Calculation of insertion loss (difference in sound level with and without the screen)
• Reporting Requirements: Outlines comprehensive documentation of test conditions, instrumentation, screen description, measurement results, and uncertainties.

Applications

ISO 11821:1997 is valuable for:

• Industrial Noise Control: Assessing and verifying the effectiveness of portable or removable screens in factories, workshops, or maintenance areas.
• Occupational Health and Safety: Helping employers and safety professionals evaluate workplace interventions to comply with noise exposure regulations.
• Product Development: Providing manufacturers of acoustic screens with a standardized method for testing and documenting product performance claims.
• Site-Specific Noise Management: Facilitating tailored noise mitigation in cases where barriers must be easily repositioned or removed to accommodate changing work layouts or processes.
• Quality Assurance: Delivering objective, comparable metrics for specifying or purchasing acoustic screens based on in situ performance.

Related Standards

Professionals working with ISO 11821:1997 may also need to consult related international standards, including:

• IEC 651, IEC 804, IEC 942, IEC 1260: Requirements for sound level meters, integrating-averaging meters, calibrators, and acoustic filters.
• ISO 10053: Measurement of office screen sound attenuation.
• ISO 10847: In situ determination of insertion loss of outdoor noise barriers.
• ISO 11546-2: Measurement of sound insulation performance of enclosures in situ.
• ISO 11957: Sound insulation testing for cabins.
• ISO 11690-2: Recommended practices for low-noise workplace design.
• ISO 140-3: Methods for laboratory measurement of airborne sound insulation.

By adhering to ISO 11821:1997, organizations and professionals ensure that sound attenuation of removable screens is measured accurately under actual use conditions, supporting effective noise management in dynamic environments.