ISO 20145:2019

Overview

ISO 20145:2019 - Pneumatic fluid power - Test methods for measuring acoustic emission pressure levels of exhaust silencers - establishes standardized acoustic test methods for pneumatic exhaust silencers. The standard defines two measurement modes: steady-state mode (constant upstream pressure; steady-state tests per ISO 6358‑1) and discharge mode (noise during pressure decrease; discharge tests per ISO 6358‑2). It is intended for manufacturers and test laboratories to evaluate and compare sound pressure levels emitted at the outlet of exhaust silencers and compressed-air discharge devices.

Key topics and technical requirements

• Two measurement methods
  • Steady-state mode: evaluates noise under constant upstream pressure (measurements normally include 6.3 bar or the maximum admissible pressure if lower).
  • Discharge mode: measures noise during pressure decay; pressure range includes 6.3 bar for comparability.
• Test bench and instrumentation
  • Test benches and upstream measurement tubes must follow ISO 6358‑1 or ISO 6358‑2 specifications.
  • Flow rate must be recorded during sound measurements; pressure measured only in the upstream pressure-measuring tube.
  • Acoustic instrumentation requirements reference IEC 61672‑1 (sound level meters), IEC 61260 (filters), and IEC 60942 (calibrators).
• Sound measurement geometry
  • Single-position measurement: microphone at 1 m from the tube centre, 60° from axis, at 1 m height.
  • Three-position measurement: three microphones on a 1 m radius arc at 15°, 60° and 105°, 1 m height - improves precision and lowers uncertainty.
• Acoustic quantities and corrections
  • Equivalent continuous A-weighted sound pressure level (LAeq) is used, over frequency range of interest (100 Hz–20 kHz).
  • Background noise correction (K1A) and environmental correction (K2A) procedures are specified; annexes provide calculation examples.
• Reporting and uncertainty
  • Test reports must include test setup, instrumentation, measured pressures/flows, LAeq results, corrections applied and measurement uncertainty. Informative annexes show example reports and uncertainty analyses.

Practical applications and who uses ISO 20145:2019

• Manufacturers of pneumatic components and exhaust silencers for R&D, product development, and quality control.
• Independent test laboratories performing repeatable acoustic certification and comparative testing.
• Acoustic engineers and compliance teams preparing noise declarations per ISO 4871 or assessing workplace noise from compressed-air systems.
• Procurement and OEMs comparing silencer performance for system integration and noise-reduction planning.

Related standards

• ISO 6358‑1, ISO 6358‑2 (flow test methods)
• ISO 11202 (noise emission measurements)
• ISO 4871 (declaration/verification of noise emission)
• IEC 61672‑1, IEC 61260, IEC 60942 (acoustic instrumentation)

ISO 20145:2019 provides a clear, standardized approach for measuring acoustic emission of pneumatic exhaust silencers, enabling reliable product comparison, compliance and noise-reduction design.