Overview
EN ISO 5135:2020 - Acoustics defines general rules for measuring sound power levels of noise from air-terminal devices, air-terminal units, dampers and valves in a reverberation test room. It is an EN-adopted version of ISO 5135:2020 and is intended for precision-grade acoustic testing referenced to ISO 3741. The standard covers test installations, measurement procedures, frequency bands and reporting requirements used to quantify HVAC noise for product development, certification and building-acoustics assessment.
Key topics and technical requirements
- Scope and applicability
- Applies to air diffusion and air distribution components (air outlets/inlets, terminal units, dampers, valves).
- Equipment must operate under steady-state conditions and occupy no more than 5% of the reverberation room volume. If >2% up to 5%, the room must be qualified with the equipment present.
- Test environment
- Measurements are performed in a reverberation test room qualified per ISO 3741 for precision determination of sound power in octave or one-third-octave bands.
- Positioning relative to reflecting planes matters (install representative of normal use; note the 1.0 m guidance for proximity to reflectors).
- Frequency range
- Typical octave-band mid-frequencies between 125 Hz and 8 000 Hz (optional down to 63 Hz); one-third-octave options also supported.
- Installations and procedures
- Specific mounting arrangements for radiation directly from equipment, via connecting ducts, and for casing-radiated noise are defined.
- Referenced measurement methods and flow/pressure requirements draw on companion documents (e.g., ISO 7235, ISO 5167) and HVAC aerodynamic test standards.
- Measurements, calculations and uncertainty
- Measurement, calculation steps and a dedicated clause on measurement uncertainty ensure repeatability and traceability.
- Reporting
- Standard specifies test-report elements to document test conditions, installation, measured sound power levels and uncertainty.
Applications - who uses it and why
- HVAC product manufacturers - to quantify and publish sound power levels for ducts, terminal devices, valves and units.
- Acoustic test laboratories - for accredited, repeatable measurements in reverberation rooms.
- Consulting engineers and building acousticians - to predict and control HVAC noise in buildings.
- Certification bodies and regulators - to verify compliance with noise performance requirements and label data sheets.
Practical uses include product development, noise optimization, regulatory compliance and inclusion of sound data in technical literature and tender documents.
Related standards
- ISO 3741 (reverberation-room sound power precision methods)
- ISO 7235 (ducted silencers and air-terminal units)
- ISO 5167 (flow measurement)
- ANSI/ASHRAE 70 & 130; EN 12238, EN 12239, EN 1751
Keywords: EN ISO 5135:2020, ISO 5135, reverberation test room, sound power level, HVAC noise, air-terminal devices, acoustic testing.