ISO 2151:2004

Overview

ISO 2151:2004 - "Acoustics - Noise test code for compressors and vacuum pumps - Engineering method (Grade 2)" specifies standardized methods for measuring, determining and declaring the noise emissions of portable and stationary compressors and vacuum pumps. The standard prescribes mounting, loading and operating conditions and defines how to report noise as sound power level and emission sound pressure level at the work station. ISO 2151 targets Grade 2 engineering accuracy and is intended for a broad range of machines including oil-lubricated, oil-free, high‑pressure and portable compressors, rotary positive-displacement blowers and centrifugal blowers (with specific pressure limits). It excludes certain low‑pressure machines, refrigerant compressors and hand‑held units.

Key Topics

• Scope and applicability
  • Covers compressors for various gases (including oxygen and acetylene), high-pressure units (>4 MPa / 40 bar), large compressors (>1 000 kW), portable/skid-mounted units and blowers up to 0.2 MPa (2 bar).
  • Excludes compressors with MAWP <0.5 bar (except acetylene), refrigerant compressors and hand‑held devices.
• Measurement objectives
  • Determine A-weighted sound power level (LWA) referenced to 1 pW and A-weighted emission sound pressure level at the work station (LpWSA).
  • Run machines under representative noisiest conditions (e.g., full-load for compressors, off-load for vacuum pumps).
• Test methods and surfaces
  • Use sound pressure (ISO 3744) or sound intensity (ISO 9614-1/2) techniques to achieve Grade 2 accuracy.
  • Definitions for reference box, measurement surface (parallelepiped or hemispherical), and measurement distance.
• Corrections and uncertainty
  • Apply background noise and environmental corrections (K1, K2).
  • Declare dual-number noise emission values (L, K) where K is total uncertainty (measurement reproducibility + production uncertainty).
• Reporting
  • Required test report content, declared noise emission forms and example reports included in annexes.

Applications

• Manufacturers: declare product noise emission values for specifications, labeling and compliance.
• Acoustic test laboratories: perform standardized Grade 2 noise tests for product development and certification.
• Procurement/specifiers and safety engineers: compare equipment, assess operator exposure and select low‑noise compressors for workshops and industrial installations.
• Product documentation: include measured sound power and emission sound pressure levels to support noise control and workplace safety planning.

Related Standards

• ISO 3744:1994 - sound power via sound pressure (free field over reflecting plane)
• ISO 9614-1/2 - sound power via sound intensity
• ISO 11201 / ISO 11202 / ISO 11203 - emission sound pressure and related methods
• ISO 4871 - declaration and verification of noise emission values
• IEC 61672-1 - sound level meter specifications

Keywords: ISO 2151:2004, noise test code, compressors, vacuum pumps, sound power level, emission sound pressure, A‑weighted, Grade 2, noise emission declaration.